1 Visualization {#occt_user_guides__visualization}
2 ========================
5 @section occt_visu_1 Introduction
7 Visualization in Open CASCADE Technology is based on the separation of:
8 * on the one hand - the data which stores the geometry and topology of the entities you want to display and select, and
9 * on the other hand - its **presentation** (what you see when an object is displayed in a scene) and **selection** (possibility to choose the whole object or its sub-parts interactively to apply application-defined operations to the selected entities).
11 Presentations are managed through the **Presentation** component, and selection through the **Selection** component.
13 **Application Interactive Services** (AIS) provides the means to create links between an application GUI viewer and the packages, which are used to manage selection and presentation, which makes management of these functionalities in 3D more intuitive and consequently, more transparent.
15 *AIS* uses the notion of the *interactive object*, a displayable and selectable entity, which represents an element from the application data. As a result, in 3D, you, the user, have no need to be familiar with any functions underlying AIS unless you want to create your own interactive objects or selection filters.
17 If, however, you require types of interactive objects and filters other than those provided, you will need to know the mechanics of presentable and selectable objects, specifically how to implement their virtual functions. To do this requires familiarity with such fundamental concepts as the sensitive primitive and the presentable object.
19 The the following packages are used to display 3D objects:
27 The packages used to display 3D objects are also applicable for visualization of 2D objects.
29 The figure below presents a schematic overview of the relations between the key concepts and packages in visualization. Naturally, "Geometry & Topology" is just an example of application data that can be handled by *AIS*, and application-specific interactive objects can deal with any kind of data.
31 @image html visualization_image003.png "Key concepts and packages in visualization"
32 @image latex visualization_image003.png "Key concepts and packages in visualization"
34 To answer different needs of CASCADE users, this User's Guide offers the following three paths in reading it.
36 * If the 3D services proposed in AIS meet your requirements, you need only read chapter 3 <a href="#occt_visu_3">AIS: Application Interactive Services</a>.
37 * If you need more detail, for example, a selection filter on another type of entity - you should read chapter 2 <a href="#occt_visu_2">Fundamental Concepts</a>, chapter 3 <a href="#occt_visu_3">AIS: Application Interactive Services</a>, and 4 <a href="#occt_visu_4">3D Presentations</a>. You may want to begin with the chapter presenting AIS.
39 @section occt_visu_2 Fundamental Concepts
41 @subsection occt_visu_2_1 Presentation
43 In Open CASCADE Technology, presentation services are separated from the data, which they represent, which is generated by applicative algorithms. This division allows you to modify a geometric or topological algorithm and its resulting objects without modifying the visualization services.
45 @subsubsection occt_visu_2_1_1 Structure of the Presentation
47 Displaying an object on the screen involves three kinds of entities:
48 * a presentable object, the *AIS_InteractiveObject*
50 * an interactive context, the *AIS_InteractiveContext*.
52 <h4>The presentable object</h4>
53 The purpose of a presentable object is to provide the graphical representation of an object in the form of *Graphic3d* structure. On the first display request, it creates this structure by calling the appropriate algorithm and retaining this framework for further display.
55 Standard presentation algorithms are provided in the *StdPrs* and *Prs3d* packages. You can, however, write specific presentation algorithms of your own, provided that they create presentations made of structures from the *Graphic3d* packages. You can also create several presentations of a single presentable object: one for each visualization mode supported by your application.
57 Each object to be presented individually must be presentable or associated with a presentable object.
60 The viewer allows interactively manipulating views of the object. When you zoom, translate or rotate a view, the viewer operates on the graphic structure created by the presentable object and not on the data model of the application. Creating Graphic3d structures in your presentation algorithms allows you to use the 3D viewers provided in Open CASCADE Technology for 3D visualisation.
62 <h4>The Interactive Context </h4>
63 The interactive context controls the entire presentation process from a common high-level API. When the application requests the display of an object, the interactive context requests the graphic structure from the presentable object and sends it to the viewer for displaying.
65 @subsubsection occt_visu_2_1_2 Presentation packages
67 Presentation involves at least the *AIS, PrsMgr, StdPrs* and *V3d* packages. Additional packages, such as *Prs3d* and *Graphic3d* may be used if you need to implement your own presentation algorithms.
69 * *AIS* package provides all classes to implement interactive objects (presentable and selectable entities).
70 * *PrsMgr* package provides low level services and is only to be used when you do not want to use the services provided by AIS. It contains all classes needed to implement the presentation process: abstract classes *Presentation* and *PresentableObject* and concrete class *PresentationManager3d*.
71 * *StdPrs* package provides ready-to-use standard presentation algorithms for specific geometries: points, curves and shapes of the geometry and topology toolkits.
72 * *Prs3d* package provides generic presentation algorithms such as wireframe, shading and hidden line removal associated with a *Drawer* class, which controls the attributes of the presentation to be created in terms of color, line type, thickness, etc.
73 * *V3d* package provides the services supported by the 3D viewer.
74 * *Graphic3d* package provides resources to create 3D graphic structures.
75 * *Visual3d* package contains classes implementing commands for 3D viewer.
76 * *DsgPrs* package provides tools for display of dimensions, relations and XYZ trihedrons.
78 @subsubsection occt_visu_2_1_3 A Basic Example: How to display a 3D object
81 Void Standard_Real dx = ...; //Parameters
82 Void Standard_Real dy = ...; //to build a wedge
83 Void Standard_Real dz = ...;
84 Void Standard_Real ltx = ...;
86 Handle(V3d_Viewer)aViewer = ...;
87 Handle(AIS_InteractiveContext)aContext;
88 aContext = new AIS_InteractiveContext(aViewer);
90 BRepPrimAPI_MakeWedge w(dx, dy, dz, ltx);
91 TopoDS_Solid & = w.Solid();
92 Handle(AIS_Shape) anAis = new AIS_Shape(S);
93 //creation of the presentable object
94 aContext -> Display(anAis);
95 //Display the presentable object in the 3d viewer.
98 The shape is created using the *BRepPrimAPI_MakeWedge* command. An *AIS_Shape* is then created from the shape. When calling the *Display* command, the interactive context calls the Compute method of the presentable object to calculate the presentation data and transfer it to the viewer. See figure below.
100 @image html visualization_image004.png "Processes involved in displaying a presentable shape"
101 @image latex visualization_image004.png "Processes involved in displaying a presentable shape"
103 @subsection occt_visu_2_2 Selection
105 Objects that may be selected graphically, are displayed as sets of sensitive primitives, which provide sensitive zones in 2D graphic space. These zones are sorted according to their position on the screen when starting the selection process.
107 @image html visualization_image006.png "A model"
108 @image latex visualization_image006.png "A model"
110 The position of the mouse is also associated with a sensitive zone. When moving within the window where objects are displayed, the areas touched by the zone of the mouse are analyzed. The owners of these areas are then highlighted or signaled by other means such as the name of the object highlighted in a list. That way, you are informed of the identity of the detected element.
112 @image html visualization_image007.png "Modeling faces with sensitive primitives"
113 @image latex visualization_image007.png "Modeling faces with sensitive primitives"
115 @image html visualization_image008.png "In a dynamic selection, each sensitive polygon is represented by its bounding rectangle"
116 @image latex visualization_image008.png "In a dynamic selection, each sensitive polygon is represented by its bounding rectangle"
118 @image html visualization_image009.png "Reference to the sensitive primitive, then to the owner"
119 @image latex visualization_image009.png "Reference to the sensitive primitive, then to the owner"
122 @subsubsection occt_visu_2_2_1 The Sensitive Primitive
124 The sensitive primitive along with the entity owner allows defining what can be made selectable, and providing the link between the applicative object and the sensitive zones defined by the 2D bounding boxes. To be dynamically selectable, an object has to be represented either as a sensitive primitive or a set of them, e.g. 2D boxes that will be included in a sorting algorithm.
126 The use of 2D boxes allows a pre-selection of the detected entities. After pre-selection, the algorithm checks which sensitive primitives are actually detected. When detected, the primitives provide their owners' identity.
128 @image html visualization_image010.png "Example of sensitive primitives"
129 @image latex visualization_image010.png "Example of sensitive primitives"
131 In the example, the sensitive line segment proposes a bounding box to the selector. During selection, positions 1 and 2 of the mouse detect the box but after sorting, only position 2 retains the line segment as selected by the algorithm.
133 When the Box associated with the position of the mouse intersects the Box of a sensitive primitive, the owner of the sensitive primitive is called and its presentation is highlighted.
135 The notion of sensitive primitive is important for the developer when defining his own classes of sensitive primitives for the chosen selection modes. The classes must contain *Areas* and *Matches* functions.
137 The former provides the list of 2D sensitive boxes representing the sensitive primitive at pre-selection and the latter determines if the detection of the primitive by the 2D boxes is valid.
140 @subsubsection occt_visu_2_2_2 Dynamic Selection
142 Dynamic selection causes objects in a view to be automatically highlighted
143 as the mouse cursor moves over them. This allows the user to be certain that the picked object
144 is the correct one. Dynamic Selection is based on the following two concepts:
146 * a Selectable Object (*AIS_InteractiveObject*)
147 * an Interactive Context
149 <h4>Selectable Object</h4>
151 A selectable object presents a given number of selection modes which can be redefined, and which will be activated or deactivated in the selection manager's selectors.
153 Note that the selection mode of a selectable object, can refer to the selection mode of the object itself or to the selection mode of its part.
155 For each selection mode, a *SelectMgr_Selection* object class is included in the selectable object. (Each selection mode establishes a priority of selection for each class of selectable object defined.)
157 The notion of **Selection** is comparable to the notion of **Display**. Just as a display contains a set of graphic primitives that allow display of the entity in a specific display mode, a **Selection** contains a set of sensitive primitives, which allow detection of the entities they are associated with.
159 <h4>Interactive Context</h4>
161 The interactive context is used to manage both selectable objects and selection processes.
163 Selection modes may be activated or de-activated for given selectable objects. Information is then provided about the status of activated/de-activated selection modes for a given object in a given selector.
165 See also <a href="#occt_visu_3">AIS: Application Interactive Services</a>.
167 Let us consider, for example, a 3D selectable shape object, which corresponds to a topological shape.
169 For this class, seven selection modes can be defined:
170 * mode 0 - selection of the shape itself
171 * mode 1 - selection of vertices
172 * mode 2 - selection of edges
173 * mode 3 - selection of wires
174 * mode 4 - selection of faces
175 * mode 5 - selection of shells
176 * mode 6 - selection of solids
177 * mode 7 - selection of compsolids
178 * mode 8 - selection of compounds
180 Selection 2 includes the sensitive primitives that model all the edges of the shape. Each of these primitives contains a reference to the edge it represents.
182 The selections may be calculated before any activation and are graph independent as long as they are not activated in a given selector. Activation of selection mode 3 in a selector associated with a view V leads to the projection of the 3D sensitive primitives contained in the selection; then the 2D areas which represent the 2D bounding boxes of these primitives are provided to the sorting process of the selector containing all the detectable areas.
184 To deactivate selection mode 3 remove all those 2D areas.
187 @subsubsection occt_visu_2_2_3 Selection Packages
189 Selection of 3D data structures is provided using various algorithms. The following selection packages exist : *SelectBasics*, *SelectMgr*, *Select3D* and *StdSelect*.
193 *SelectBasics* package contains the basic classes of the selection:
194 * the main definition of a sensitive primitive: *SensitiveEntity*, which is a selectable entity in a view;
195 * the definition of a sensitive primitive owner: *EntityOwner* this entity relates the primitive to the application entity which is to be selected in the view.
196 * the algorithm used for sorting sensitive boxes: *SortAlgo*
198 *EntityOwner* is used to establish a link from *SensitiveEntity* to application-level objects. For example, *SelectMgr_EntityOwner* (see below) class holds a pointer to corresponding *SelectableObject*.
200 ### Standard Selections
202 *Select3D* package provides definition of all 3D standard sensitive primitives such as point, curve and face. All these classes inherit from 3D *SensitiveEntry* from *SelectBasics* with an additional method, which allows recovery of the bounding boxes in the 2D graphic selection space, if required. This package also includes the 3D-2D projector.
204 *StdSelect* package provides standard uses of the classes described above and main tools used to prevent the developer from redefining the selection objects. In particular, *StdSelect* includes standard modes for selection of topological shapes, definition of several filter standard <i> Selection2d.ap </i> classes and 3D viewer selectors.
206 Note that each new Interactive Object must have all its selection modes defined.
208 ### Selection Management
210 *SelectMgr* package is used to manage the whole dynamic selection process.
212 It provides low level services and classes *SelectMgr_SelectionManager* and *SelectMgr_ViewerSelector*. They can be used when you do not want to use the services provided by *AIS*.
214 There are also implementations of *ViewerSelector* interface for 3D selection in *StdSelect* package: *ViewerSelector3d*.
216 *SelectMgr* manages the process of dynamic selection through the following services:
218 * Activating and deactivating selection modes for Interactive Objects.
219 * Adding and removing viewer selectors.
220 * Definitions of abstract filter classes.
222 The principle of graphic selection consists in representing the objects which you want to select by a bounding box in the selection view.
223 The object is selected when you use the mouse to designate the zone produced by the object.
225 To realize this, the application creates a selection structure which is independent of the point of view.
226 This structure is made up of sensitive primitives which have one owner object associated to each of them.
227 The role of the sensitive primitive is to reply to the requests of the selection algorithm whereas the owner's purpose is to make the link between the sensitive primitive and the object to be selected.
228 Each selection structure corresponds to a selection mode which defines the elements that can be selected.
230 ### Example: Selection of a Geometric Model
232 For example, to select a complete geometric model, the application can create a sensitive primitive for each face of the interactive object representing the geometric model.
233 In this case, all the primitives share the same owner.
234 On the other hand, to select an edge in a model, the application must create one sensitive primitive per edge.
238 void InteractiveBox::ComputeSelection (const Handle(SelectMgr_Selection)& theSel,
239 const Standard_Integer theMode)
243 case 0: // locating the whole box by making its faces sensitive
245 Handle(SelectMgr_EntityOwner) anOwner = new SelectMgr_EntityOwner (this, 5);
246 for (Standard_Integer anIt = 1; anIt <= aFacesNb; anIt++)
248 theSel->Add (new Select3D_SensitiveFace (anOwner,[array of the vertices] face I);
251 case 1: // locating the edges
253 for (Standard_Integer anIt = 1; anIt <= 12; anIt++)
256 Handle(mypk_EdgeOwner) anOwner = new mypk_EdgeOwner (this, anIt, 6); // 6->priority
257 theSel->Add (new Select3D_SensitiveSegment (anOwner, firstpt (anIt), lastpt (anIt));
264 The algorithms for creating selection structures store the sensitive primitives in a <i>SelectMgr_Selection</i> object.
265 To do this, a set of ready-made sensitive primitives is supplied in the <i>Select3D</i>package.
266 New sensitive primitives can be defined through inheritance from <i>SensitiveEntity</i>.
267 For the application to make its own objects selectable, it must define owner classes inheriting <i>SelectMgr_EntityOwner</i>.
269 Selection structures for any interactive object are generated in <i>ComputeSelection()</i> method.
270 In the example below there are different modes of selection on the topological shape contained within the interactive object,
271 selection of the shape itself, the vertices, the edges, the wires, the faces.
274 void MyPack_MyClass::ComputeSelection(
275 const Handle(SelectMgr_Selection)& theaSelection,
276 const Standard_Integer theMode)
281 StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_SHAPE);
284 StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_VERTEX);
287 StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_EDGE);
290 StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_WIRE);
293 StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_FACE);
299 The <i>StdSelect_BRepSelectionTool</i> object provides a high level service which will make the topological shape <i>myShape</i> selectable when the <i>AIS_InteractiveContext</i> is asked to display your object.
303 The traditional way of highlighting selected entity owners adopted by Open CASCADE Technology assumes that each entity owner highlights itself on its own. This approach has two drawbacks:
305 * Each entity owner has to maintain its own <i>Prs3d_Presentation object</i>, that results in large memory overhead for thousands of owners.
306 * Drawing selected owners one by one is not efficient from the OpenGL usage viewpoint.
308 That is why a different method has been introduced.
309 On the basis of <i>SelectMgr_EntityOwner::IsAutoHilight()</i> return value <i>AIS_LocalContext</i>
310 object either uses the traditional way of highlighting (<i>IsAutoHilight()</i> returned true)
311 or groups such owners according to their Selectable Objects and finally calls <i> SelectMgr_SelectableObject::HilightSelected()</i> or
312 <i>ClearSelected()</i>, passing a group of owners as an argument.
314 Hence, an application can derive its own interactive object and redefine <i> HilightSelected()</i>,
315 <i>ClearSelected()</i> and <i>HilightOwnerWithColor()</i> virtual methods
316 to take advantage of such OpenGL technique as arrays of primitives.
317 In any case, these methods should at least have empty implementation.
319 The <i>AIS_LocalContext::UpdateSelected (const Handle(AIS_InteratciveObject)&, Standard_Boolean)</i>
320 method can be used for efficient redrawing a selection presentation for a given interactive object from an application code.
322 Additionally, the <i>SelectMgr_SelectableObject::ClearSelections()</i> method now accepts an optional Boolean argument.
323 This parameter defines whether all object selections should be flagged for further update or not.
324 This improved method can be used to re-compute an object selection (without redisplaying the object completely)
325 when some selection mode is activated not for the first time.
327 @subsubsection occt_visu_2_2_4 How to use dynamic selection
329 Several operations must be performed prior to using dynamic selection:
330 1. Implement specific sensitive primitives if those defined in Select3D are not sufficient. These primitives must inherit from *SensitiveEntity* from *SelectBasics* or from a suitable Select3D sensitive entity class when a projection from 3D to 2D is necessary.
331 2. Define all the owner types, which will be used, and the classes of selectable objects, i.e. the number of possible selection modes for these objects and the calculation of the decomposition of the object into sensitive primitives of all the primitives describing this mode. It is possible to define only one default selection mode for a selectable object if this object is to be selectable in a unique way.
332 3. Install the process, which provides the user with the identity of the owner of the detected entities in the selection loop.
334 When all these steps have been carried out, follow the procedure below:
335 1. Create an interactive context.
336 2. Create the selectable objects and calculate their various possible selections.
337 3. Load these selectable objects in the interactive context. The objects may be common to all the selectors, i.e. they will be seen by all the selectors in the selection manager, or local to one selector or more.
338 4. Activate or deactivate the objects' selection modes in the selector(s). When activating a selection mode in a selector for a given object, the manager sends the order to make the sensitive primitives in this selector selectable. If the primitives are to projected from 3D to 2D, the selector calls the specific method used to carry out this projection.
340 At this stage, the selection of selectable entities in the selectors is available.
341 The selection loop informs constantly the selectors with the position of the mouse and questions them about the detected entities.
343 Let us suppose that you create an application that displays houses in a viewer of the V3d package and you want to select houses or parts of these houses (windows, doors, etc.) in the graphic window.
344 You define a selectable object called *House* and propose four possible selection modes for this object:
345 1. selection of the house itself;
346 2. selection of the rooms
347 3. selection of the walls
348 4. selection of the doors.
350 You have to write the method, which calculates the four selections above, i.e. the sensitive primitives which are activated when the mode is.
351 You must define the class *Owner* specific to your application. This class will contain the reference to the house element it represents: wall, door or room. It inherits from *EntityOwner* from *SelectMgr*.
352 For example, let us consider a house with the following representation:
354 @image html visualization_image011.png "Selection of rooms in a house"
355 @image latex visualization_image011.png "Selection of rooms in a house"
357 To build the selection, which corresponds to the mode "selection of the rooms"
358 (selection 2 in the list of selection modes), use the following procedure:
362 Void House::ComputeSelection
363 (Const Handle(SelectMgr_Selection)& Sel,
364 const Standard_Integer mode {
366 case 0: //Selection of the rooms
368 for(Standard_Integer i = 1; i <= myNbRooms; i++)
370 //for every room, create an instance of the owner, the given room and its name.
371 Handle(RoomOwner) aRoomOwner = new RoomOwner (Room(i), NameRoom(i));
372 //Room() returns a room and NameRoom() returns its name.
373 Handle(Select3d_SensitiveBox) aSensitiveBox;
374 aSensitiveBox = new Select3d_SensitiveBox
375 (aRoomOwner, Xmin, Ymin, Zmin, Xmax, Ymax, Zmax);
376 Sel -> Add(aSensitiveBox);
379 Case 1: ... //Selection of the doors
381 ) // ComputeSelection
384 @image html visualization_image012.png "Activated sensitive boxes corresponding to selection mode 0 (selection of rooms)"
385 @image latex visualization_image012.png "Activated sensitive boxes corresponding to selection mode 0 (selection of rooms)"
387 @image html visualization_image013.png "Activated sensitive rectangles in the selector during dynamic selection in view 1"
388 @image latex visualization_image013.png "Activated sensitive rectangles in the selector during dynamic selection in view 1"
390 @image html visualization_image014.png "Activated sensitive polygons corresponding to selection mode 1 (selection of doors)"
391 @image latex visualization_image014.png "Activated sensitive polygons corresponding to selection mode 1 (selection of doors)"
393 @image html visualization_image015.png "Sensitive rectangles in the selector during dynamic selection in view 2"
394 @image latex visualization_image015.png "Sensitive rectangles in the selector during dynamic selection in view 2"
396 @section occt_visu_3 Application Interactive Services
397 @subsection occt_visu_3_1 Introduction
399 Application Interactive Services allow managing presentations and dynamic selection in a viewer in a simple and transparent manner.
401 The central entity for management of visualization and selections is the **Interactive Context**. It is connected to the main viewer (and if need be, the trash bin viewer). It has two operating modes: the Neutral Point and the local visualization and selection context.
403 The neutral point, which is the default mode, allows easily visualizing and selecting interactive objects loaded into the context.
405 **Local Contexts** can be opened to prepare and use a temporary selection environment without disturbing
406 the neutral point. It is possible to choose the interactive objects, which you want to act on, the selection modes, which you want to activate, and the temporary visualizations, which you will execute.
408 When the operation is finished, you close the current local context and return to the state
409 in which you were before opening it (neutral point or previous local context).
411 **Interactive Objects** are the entities, which are visualized and selected. You can use classes of standard interactive objects for which all necessary functions have already been programmed, or you can implement your own classes of interactive objects, by respecting a certain number of rules and conventions described below.
413 @image html visualization_image016.png
414 @image latex visualization_image016.png
416 An Interactive Object is a "virtual" entity, which can be presented and selected. An Interactive Object can have a certain number of specific graphic attributes, such as visualization mode, color and material.
418 When an Interactive Object is visualized, the required graphic attributes are taken from its own **Drawer** if it has the required custom attributes or otherwise from the context drawer.
420 @image html visualization_image017.png
421 @image latex visualization_image017.png
423 It can be necessary to filter the entities to be selected. Consequently there are **Filter** entities, which allow refining the dynamic detection context. Some of these filters can be used at the Neutral Point, others only in an open local context. It is possible to program custom filters and load them into the interactive context.
425 @subsection occt_visu_3_2 Interactive objects
427 Entities which are visualized and selected in the AIS viewer are objects. They connect the underlying reference geometry of a model to its graphic representation in *AIS*. You can use the predefined OCCT classes of standard interactive objects, for which all necessary functions have already been programmed, or, if you are an advanced user, you can implement your own classes of interactive objects.
429 @subsubsection occt_visu_3_2_1 Presentations
431 An interactive object can have as many presentations as its creator wants to give it.
433 3D presentations are managed by PresentationManager3D. As this is transparent in AIS, the user does not have to worry about it.
435 A presentation is identified by an index and by the reference to the Presentation Manager which it depends on.
437 By convention, the default mode of representation for the Interactive Object has index 0.
439 @image html visualization_image018.png
440 @image latex visualization_image018.png
442 Calculation of different presentations of an interactive object is done by the *Compute* functions inheriting from *PrsMgr_ PresentableObject::Compute* functions. They are automatically called by *PresentationManager* at a visualization or an update request.
444 If you are creating your own type of interactive object, you must implement the Compute function in one of the following ways:
449 void PackageName_ClassName::Compute
450 (const Handle(PrsMgr_PresentationManager3d)& aPresentationManager,
451 const Handle(Prs3d_Presentation)& aPresentation,
452 const Standard_Integer aMode = 0);
455 #### For hidden line removal (HLR) mode in 3D:
457 void PackageName_ClassName::Compute
458 (const Handle(Prs3d_Projector)& aProjector,
459 const Handle(Prs3d_Presentation)& aPresentation);
462 @subsubsection occt_visu_3_2_2 Hidden Line Removal
464 The view can have two states: the normal mode or the computed mode (Hidden Line Removal mode). When the latter is active, the view looks for all presentations displayed in the normal mode, which have been signalled as accepting HLR mode. An internal mechanism allows calling the interactive object's own *Compute*, that is projector function.
466 By convention, the Interactive Object accepts or rejects the representation of HLR mode. It is possible to make this declaration in one of two ways:
468 * Initially by using one of the values of the enumeration *PrsMgr_TypeOfPresentation*:
469 * *PrsMgr_TOP_AllView*,
470 * *PrsMgr_TOP_ProjectorDependant*
472 * Later by using the function *PrsMgr_PresentableObject::SetTypeOfPresentation*
474 *AIS_Shape* class is an example of an interactive object that supports HLR representation. It supports two types of the HLR algorithm:
475 * the polygonal algorithm based on the shape's triangulation;
476 * the exact algorithm that works with the shape's real geometry.
478 The type of the HLR algorithm is stored in *AIS_Drawer* of the shape. It is a value of the *Prs3d_TypeOfHLR* enumeration and can be set to:
479 * *Prs3d_TOH_PolyAlgo* for a polygonal algorithm;
480 * *Prs3d_TOH_Algo* for an exact algorithm;
481 * *Prs3d_TOH_NotSet* if the type of algorithm is not set for the given interactive object instance.
483 The type of the HLR algorithm used for *AIS_Shape* can be changed by calling the *AIS_Shape::SetTypeOfHLR()* method.
485 The current HLR algorithm type can be obtained using *AIS_Shape::TypeOfHLR()* method is to be used.
487 These methods get the value from the drawer of *AIS_Shape*. If the HLR algorithm type in the *AIS_Drawer* is set to *Prs3d_TOH_NotSet*, the *AIS_Drawer* gets the value from the default drawer of *AIS_InteractiveContext*.
489 So it is possible to change the default HLR algorithm used by all newly displayed interactive objects. The value of the HLR algorithm type stored in the context drawer can be *Prs3d_TOH_Algo* or *Prs3d_TOH_PolyAlgo*. The polygonal algorithm is the default one.
491 @subsubsection occt_visu_3_2_3 Presentation modes
493 There are four types of interactive objects in AIS:
494 * the "construction element" or Datum,
495 * the Relation (dimensions and constraints)
497 * the None type (when the object is of an unknown type).
499 Inside these categories, additional characterization is available by means of a signature (an index.) By default, the interactive object has a NONE type and a signature of 0 (equivalent to NONE.) If you want to give a particular type and signature to your interactive object, you must redefine two virtual functions:
500 * *AIS_InteractiveObject::Type*
501 * *AIS_InteractiveObject::Signature*.
503 **Note** that some signatures are already used by "standard" objects provided in AIS (see the <a href="#occt_visu_3_5">list of Standard Interactive Object Classes</a>).
505 The interactive context can have a default mode of representation for the set of interactive objects. This mode may not be accepted by a given class of objects.
507 Consequently, to get information about this class it is necessary to use virtual function *AIS_InteractiveObject::AcceptDisplayMode*.
511 The functions *AIS_InteractiveContext::SetDisplayMode* and *AIS_InteractiveContext::UnsetDisplayMode* allow setting a custom display mode for an objects, which can be different from that proposed by the interactive context.
515 At dynamic detection, the presentation echoed by the Interactive Context, is by default the presentation already on the screen.
517 The functions *AIS_InteractiveObject::SetHilightMode* and *AIS_InteractiveObject::UnSetHilightMode* allow specifying the display mode used for highlighting (so called highlight mode), which is valid independently from the active representation of the object. It makes no difference whether this choice is temporary or definitive.
519 Note that the same presentation (and consequently the same highlight mode) is used for highlighting *detected* objects and for highlighting *selected* objects, the latter being drawn with a special *selection color* (refer to the section related to *Interactive Context* services).
521 For example, you want to systematically highlight the wireframe presentation of a shape - non regarding if it is visualized in wireframe presentation or with shading. Thus, you set the highlight mode to *0* in the constructor of the interactive object. Do not forget to implement this representation mode in the *Compute* functions.
524 If you do not want an object to be affected by a *FitAll* view, you must declare it infinite; you can cancel its "infinite" status using *AIS_InteractiveObject::SetInfiniteState* and *AIS_InteractiveObject::IsInfinite* functions.
526 Let us take for example the class called *IShape* representing an interactive object :
529 myPk_IShape::myPK_IShape
530 (const TopoDS_Shape& SH, PrsMgr_TypeOfPresentation aType):
531 AIS_InteractiveObject(aType), myShape(SH), myDrwr(new AIS_Drawer()) {SetHilightMode(0);}
532 void myPk_IShape::Compute
533 (const Handle(PrsMgr_PresentationManager3d) & PM,
534 const Handle(Prs3d_Presentation)& P,
535 const Standard_Integer TheMode)
539 StdPrs_WFDeflectionShape::Add (P,myShape,myDrwr); //algo for calculation of wireframe presentation break;
541 StdPrs_ShadedShape::Add (P,myShape,myDrwr); //algo for calculation of shading presentation.
545 void myPk_IsShape::Compute
546 (const Handle(Prs3d_Projector)& Prj,
547 const Handle(Prs3d_Presentation) P)
549 StdPrs_HLRPolyShape::Add(P,myShape,myDrwr);
550 //Hidden line mode calculation algorithm
554 @subsubsection occt_visu_3_2_4 Selection
556 An interactive object can have an indefinite number of selection modes, each representing a "decomposition" into sensitive primitives; each primitive has an Owner (*SelectMgr_EntityOwner*) which allows identifying the exact entity which has been detected (see <a href="#occt_visu_3_6"> Dynamic Selection</a> chapter).
558 The set of sensitive primitives, which correspond to a given mode, is stocked in a SELECTION (*SelectMgr_Selection*).
560 Each Selection mode is identified by an index. By Convention, the default selection mode that allows us to grasp the Interactive object in its entirety is mode *0*.
562 The calculation of Selection primitives (or sensitive primitives) is done by the intermediary of a virtual function, *ComputeSelection*. This should be implemented for each type of interactive object on which you want to make different type selections using the function *AIS_ConnectedInteractive::ComputeSelection*.
564 A detailed explanation of the mechanism and the manner of implementing this function has been given in <a href="#occt_visu_3_6"> Dynamic Selection</a> chapter.
566 Moreover, just as the most frequently manipulated entity is *TopoDS_Shape*, the most used Interactive Object is *AIS_Shape*. You will see below activation functions for standard selection modes are proposed in the Interactive context (selection by vertex, by edges etc). To create new classes of interactive object with the same behavior as *AIS_Shape* - such as vertices and edges - you must redefine the virtual function *AIS_ConnectedInteractive::AcceptShapeDecomposition*.
568 You can change the default selection mode index of an Interactive Object using the following functions:
569 * *AIS_InteractiveObject::HasSelectionMode* checks if there is a selection mode;
570 * *AIS_InteractiveObject::SelectionMode* check the current selection mode;
571 * *AIS_InteractiveContext::SetSelectionMode* sets a selection mode;
572 * *AIS_InteractiveContext::UnsetSelectionMode* unsets a selection mode.
574 These functions can be useful if you decide that the *0* mode used by default will not do. In the same way, you can temporarily change the priority of certain interactive objects for selection of 0 mode to facilitate detecting them graphically using the following functions:
575 * *AIS_InteractiveObject::HasSelectionPriority* checks if there is a selection priority setting for the owner;
576 * *AIS_InteractiveObject::SelectionPriority* checks the current priority;
577 * *AIS_InteractiveObject::SetSelectionPriority* sets a priority;
578 * *AIS_InteractiveObject::UnsetSelectionPriority* unsets the priority.
581 @subsubsection occt_visu_3_2_5 Graphic attributes
583 Graphic attributes manager, or *AIS Drawer*, stores graphic attributes for specific interactive objects and for interactive objects controlled by interactive context.
585 Initially, all drawer attributes are filled out with the predefined values which will define the default 3D object appearance.
587 When an interactive object is visualized, the required graphic attributes are first taken from its own drawer if one exists, or from the context drawer if no specific drawer for that type of object exists.
589 Keep in mind the following points concerning graphic attributes:
590 * Each interactive object can have its own visualization attributes.
591 * The set of graphic attributes of an interactive object is stocked in an *AIS_Drawer*, which is only a *Prs3d_Drawer* with the possibility of a link to another drawer
592 * By default, the interactive object takes the graphic attributes of the context in which it is visualized (visualization mode, deflection values for the calculation of presentations, number of isoparameters, color, type of line, material, etc.)
593 * In the *AIS_InteractiveObject* abstract class, standard attributes including color, line thickness, material, and transparency have been privileged. Consequently, there is a certain number of virtual functions, which allow acting on these attributes. Each new class of interactive object can redefine these functions and change the behavior of the class.
595 @image html visualization_image019.png "Figure 13. Redefinition of virtual functions for changes in AIS_Point"
596 @image latex visualization_image019.png "Figure 13. Redefinition of virtual functions for changes in AIS_Point"
598 @image html visualization_image020.png "Figure 14. Redefinition of virtual functions for changes in AIS_Shape."
599 @image latex visualization_image020.png "Figure 14. Redefinition of virtual functions for changes in AIS_Shape."
601 The following virtual functions provide settings for color, width, material and transparency:
602 * *AIS_InteractiveObject::UnsetColor*
603 * *AIS_InteractiveObject::SetWidth*
604 * *AIS_InteractiveObject::UnsetWidth*
605 * *AIS_InteractiveObject::SetMaterial (const Graphic3d_NameOfPhysicalMaterial & aName)*
606 * *AIS_InteractiveObject::SetMaterial (const Graphic3d_MaterialAspect & aMat)*
607 * *AIS_InteractiveObject::UnsetMaterial*
608 * *AIS_InteractiveObject::SetTransparency*
609 * *AIS_InteractiveObject::UnsetTransparency*
611 For other types of attribute, it is appropriate to change the Drawer of the object directly using:
612 * *AIS_InteractiveObject::SetAttributes*
613 * *AIS_InteractiveObject::UnsetAttributes*
615 It is important to know which functions may imply the recalculation of presentations of the object.
617 If the presentation mode of an interactive object is to be updated, a flag from *PrsMgr_PresentableObject* indicates this.
619 The mode can be updated using the functions *Display* and *Redisplay* in *AIS_InteractiveContext*.
621 @subsubsection occt_visu_3_2_6 Complementary Services
623 When you use complementary services for interactive objects, pay special attention to the cases mentioned below.
625 #### Change the location of an interactive object
627 The following functions allow temporarily "moving" the representation and selection of Interactive Objects in a view without recalculation.
628 * *AIS_InteractiveContext::SetLocation*
629 * *AIS_InteractiveContext::ResetLocation*
630 * *AIS_InteractiveContext::HasLocation*
631 * *AIS_InteractiveContext::Location*
633 #### Connect an interactive object to an applicative entity
635 Each Interactive Object has functions that allow attributing it an *Owner* in form of a *Transient*.
636 * *AIS_InteractiveObject::SetOwner*
637 * *AIS_InteractiveObject::HasOwner*
638 * *AIS_InteractiveObject::Owner*
640 An interactive object can therefore be associated or not with an applicative entity, without affecting its behavior.
642 #### Resolving coincident topology
644 Due to the fact that the accuracy of three-dimensional graphics coordinates has a finite resolution the elements of topological objects can coincide producing the effect of "popping" some elements one over another.
646 To the problem when the elements of two or more Interactive Objects are coincident you can apply the polygon offset. It is a sort of graphics computational offset, or depth buffer offset, that allows you to arrange elements (by modifying their depth value) without changing their coordinates. The graphical elements that accept this kind of offsets are solid polygons or displayed as boundary lines and points. The polygons could be displayed as lines or points by setting the appropriate interior style.
648 The method *AIS_InteractiveObject::SetPolygonOffsets (const Standard_Integer aMode, const Standard_Real aFactor, const Standard_Real aUnits)* allows setting up the polygon offsets.
650 The parameter *aMode* can contain various combinations of *Aspect_PolygonOffsetMode* enumeration elements:
658 The combination of these elements defines the polygon display modes that will use the given offsets. You can switch off the polygon offsets by passing *Aspect_POM_Off*. Passing *Aspect_POM_None* allows changing the *aFactor* and *aUnits* values without changing the mode. If *aMode* is different from *Aspect_POM_Off*, the *aFactor* and *aUnits* arguments are used by the graphics renderer to calculate the depth offset value:
660 offset = aFactor * m + aUnits * r
662 where *m* is the maximum depth slope for the currently displayed polygons, r is the minimum depth resolution (implementation-specific).
664 Negative offset values move polygons closer to the viewer while positive values shift polygons away.
668 This method has a side effect - it creates its own shading aspect if not yet created, so it is better to set up the object shading aspect first.
670 You can use the following functions to obtain the current settings for polygon offsets:
672 void AIS_InteractiveObject::PolygonOffsets
673 (Standard_Integer &aMode,
674 Standard_Real &aFactor,
675 Standard_Real &aUnits)
676 Standard_Boolean AIS_InteractiveObject::HasPolygonOffsets()
679 The same operation could be performed for the interactive object known by the *AIS_InteractiveContext* with the following methods:
681 void AIS_InteractiveContext::SetPolygonOffsets
682 (const Handle(AIS_InteractiveObject) &anObj,
683 const Standard_Integer aMode,
684 const Standard_Real aFactor,
685 const Standard_Real aUnits)
686 void AIS_InteractiveContext::PolygonOffsets
687 (const Handle(AIS_InteractiveObject) &anObj,
688 Standard_Integer &aMode,
689 Standard_Real &aFactor,
690 Standard_Real &aUnits)
691 Standard_Boolean AIS_InteractiveContext::HasPolygonOffsets
692 (const Handle(AIS_InteractiveObject) &anObj)
695 @subsection occt_visu_3_3 Interactive Context
697 @subsubsection occt_visu_3_3_1 Rules
699 The Interactive Context allows managing in a transparent way the graphic and **selectable** behavior of interactive objects in one or more viewers. Most functions which allow modifying the attributes of interactive objects, and which were presented in the preceding chapter, will be looked at again here.
701 There is one essential rule to follow: the modification of an interactive object, which is already known by the Context, must be done using Context functions. You can only directly call the functions available for an interactive object if it has not been loaded into an Interactive Context.
704 Handle (AIS_Shape) TheAISShape = new AIS_Shape (ashape);
705 myIntContext->Display(TheAISShape);
706 myIntContext->SetDisplayMode(TheAISShape ,1);
707 myIntContext->SetColor(TheAISShape,Quantity_NOC_RED);
713 Handle (AIS_Shape) TheAISShape = new AIS_Shape (ashape);
714 TheAISShape->SetColor(Quantity_NOC_RED);
715 TheAISShape->SetDisplayMode(1);
716 myIntContext->Display(TheAISShape);
719 @subsubsection occt_visu_3_3_2 Groups of functions
721 **Neutral Point** and **Local Context** constitute the two operating modes or states of the **Interactive Context**, which is the central entity which pilots visualizations and selections.
723 The **Neutral Point**, which is the default mode, allows easily visualizing and selecting interactive objects, which have been loaded into the context. Opening **Local contexts** allows preparing and using a temporary selection environment without disturbing the neutral point.
725 A set of functions allows choosing the interactive objects which you want to act on, the selection modes which you want to activate, and the temporary visualizations which you will execute. When the operation is finished, you close the current local context and return to the state in which you were before opening it (neutral point or previous local context).
727 The Interactive Context is composed of many functions, which can be conveniently grouped according to the theme:
728 * management proper to the context;
729 * management in the local context;
730 * presentations and selection in open/closed context;
731 * selection strictly speaking.
733 Some functions can only be used in open Local Context; others in closed local context; others do not have the same behavior in one state as in the other.
735 @subsubsection occt_visu_3_3_3 Management of the Interactive Context
737 The **Interactive Context** is made up of a **Principal Viewer** and, optionally, a trash bin or **Collector Viewer**.
739 An interactive object can have a certain number of specific graphic attributes, such as visualization mode, color, and material. Correspondingly, the interactive context has a set of graphic attributes, the *Drawer*, which is valid by default for the objects it controls.
741 When an interactive object is visualized, the required graphic attributes are first taken from the object's own <i>Drawer</i> if one exists, or from the context drawer for the others.
743 The following adjustable settings allow personalizing the behavior of presentations and selections:
744 * Default Drawer, containing all the color and line attributes which can be used by interactive objects, which do not have their own attributes.
745 * Default Visualization Mode for interactive objects. By default: *mode 0* ;
746 * Highlight color of entities detected by mouse movement. By default: *Quantity_NOC_CYAN1*;
747 * Pre-selection color. By default: *Quantity_NOC_GREEN*;
748 * Selection color (when you click on a detected object). By default: *Quantity_NOC_GRAY80*;
749 * Sub-Intensity color. By default: *Quantity_NOC_GRAY40*.
751 All of these settings can be modified by functions proper to the Context.
753 When you change a graphic attribute pertaining to the Context (visualization mode, for example), all interactive objects, which do not have the corresponding appropriate attribute, are updated.
755 Let us examine the case of two interactive objects: *obj1* and *obj2*:
758 TheCtx->Display(obj1,Standard_False); // False = no viewer update
759 TheCtx->Display(obj2,Standard_True); // True = viewer update
760 TheCtx->SetDisplayMode(obj1,3,Standard_False);
761 TheCtx->SetDisplayMode(2);
762 // obj2 is visualised in mode 2 (if it accepts this mode)
763 // obj1 stays visualised in its mode 3.
766 *PresentationManager3D* and *Selector3D*, which manage the presentation and selection of present interactive objects, are associated to the main Viewer. The same is true of the optional Collector.
768 @subsection occt_visu_3_4 Local Context
770 @subsubsection occt_visu_3_4_1 Rules and Conventions
772 * Opening a local context allows preparing an environment for temporary presentations and selections, which will disappear once the local context is closed.
773 * It is possible to open several local contexts, but only the last one will be active.
774 * When you close a local context, the previous one, which is still on the stack, is activated again. If none is left, you return to Neutral Point.
775 * Each local context has an index created when the context opens. You should close the local context, which you have opened.
777 The interactive object, which is used the most by applications, is *AIS_Shape*. Consequently, standard functions are available which allow you to easily prepare selection operations on the constituent elements of shapes (selection of vertices, edges, faces etc) in an open local context. The selection modes specific to "Shape" type objects are called **Standard Activation Mode**. These modes are only taken into account in open local context and only act on interactive objects which have redefined the virtual function *AcceptShapeDecomposition()* so that it returns *TRUE*.
778 * Objects, which are temporarily in a local context, are not recognized by other local contexts a priori. Only objects visualized in Neutral Point are recognized by all local contexts.
779 * The state of a temporary interactive object in a local context can only be modified while another local context is open.
783 The specific modes of selection only concern the interactive objects, which are present in the Main Viewer. In the Collector, you can only locate interactive objects, which answer positively to the positioned filters when a local context is open, however, they are never decomposed in standard mode.
785 @subsubsection occt_visu_3_4_2 Management of Local Context
787 The local context can be opened using method *AIS_InteractiveContext::OpenLocalContext*. The following options are available:
788 * *UseDisplayedObjects*: allows loading the interactive objects visualized at Neutral Point in the opened local context. If *FALSE*, the local context is empty after being opened. If *TRUE*, the objects at Neutral Point are modified by their default selection mode.
789 * *AllowShapeDecomposition*: *AIS_Shape* allows or prevents decomposition in standard shape location mode of objects at Neutral Point, which are type-privileged (see <a href="#occt_visu_3_2_4"> Selection</a> chapter). This Flag is only taken into account when *UseDisplayedObjects* is *TRUE*.
790 * *AcceptEraseOfObjects*: authorizes other local contexts to erase the interactive objects present in this context. This option is rarely used. The last option has no current use.
792 This function returns the index of the created local context. It should be kept and used when the context is closed.
794 To load objects visualized at Neutral Point into a local context or remove them from it use methods
796 AIS_InteractiveContext::UseDisplayedObjects
797 AIS_InteractiveContext::NotUseDisplayedObjects
799 Closing Local Contexts is done by:
801 AIS_InteractiveContext::CloseLocalContext
802 AIS_InteractiveContext::CloseAllContexts
806 When the index is not specified in the first function, the current Context is closed. This option can be dangerous, as other Interactive Functions can open local contexts without necessarily warning the user. For greater security, you have to close the context with the index given on opening.
808 To get the index of the current context, use function *AIS_InteractiveContext::IndexOfCurrentLocal*. It allows closing all open local contexts at one go. In this case, you find yourself directly at Neutral Point.
810 When you close a local context, all temporary interactive objects are deleted, all selection modes concerning the context are canceled, and all content filters are emptied.
813 @subsubsection occt_visu_3_4_3 Presentation in a Neutral Point
815 You must distinguish between the **Neutral Point** and the **Open Local Context** states. Although the majority of visualization functions can be used in both situations, their behavior is different.
817 Neutral Point should be used to visualize the interactive objects, which represent and select an applicative entity. Visualization and Erasing orders are straightforward:
820 AIS_InteractiveContext::Display
821 (const Handle(AIS_InteractiveObject)& anIobj,
822 const Standard_Boolean updateviewer=Standard_True);
824 AIS_InteractiveContext::Display
825 (const Handle(AIS_InteractiveObject)& anIobj,
826 const Standard_Integer amode,
827 const Standard_Integer aSelectionMode,
828 const Standard_Boolean updateviewer = Standard_True,
829 const Standard_Boolean allowdecomposition = Standard_True);
831 AIS_InteractiveContext::Erase
832 AIS_InteractiveContext::EraseMode
833 AIS_InteractiveContext::ClearPrs
834 AIS_InteractiveContext::Redisplay
835 AIS_InteractiveContext::Remove
836 AIS_InteractiveContext::EraseAll
837 AIS_InteractiveContext::Hilight
838 AIS_InteractiveContext::HilightWithColor
841 Bear in mind the following points:
842 * It is recommended to display and erase interactive objects when no local context is opened, and open a local context for local selection only.
843 * The first *Display* function among the two ones available in *InteractiveContext* visualizes the object in its default mode (set with help of SetDisplayMode() method of InteractiveObject prior to Display() call), or in the default context mode, if applicable. If it has neither, the function displays it in 0 presentation mode. The object's default selection mode is automatically activated (0 mode by convention).
844 * Activating the displayed object by default can be turned off with help of *SetAutoActivateSelection()* method. This might be efficient if you are not interested in selection immediately after displaying an object.
845 * The second *Display* function should only be used in Neutral Point to visualize a supplementary mode for the object, which you can erase by *EraseMode (...)*. You activate the selection mode. This is passed as an argument. By convention, if you do not want to activate a selection mode, you must set the *SelectionMode* argument to -1. This function is especially interesting in open local context, as we will see below.
846 * In Neutral Point, it is not advisable to activate other selection modes than the default selection one. It is preferable to open a local context in order to activate particular selection modes.
847 * When you call *Erase(Interactive object)* function, the *PutIncollector* argument, which is *FALSE* by default, allows you to visualize the object directly in the Collector and makes it selectable (by activation of 0 mode). You can nonetheless block its passage through the Collector by changing the value of this option. In this case, the object is present in the Interactive Context, but is not seen anywhere.
848 * *Erase()* with *putInCollector = Standard_True* might be slow as it recomputes the object presentation in the Collector. Set *putInCollector* to *Standard_False* if you simply want to hide the object's presentation temporarily.
849 * Visualization attributes and graphic behavior can be modified through a set of functions similar to those for the interactive object (color, thickness of line, material, transparency, locations, etc.) The context then manages immediate and deferred updates.
850 * Call *Remove()* method of *InteractiveContext* as soon as the interactive object is no longer needed and you want to destroy it.. Otherwise, references to *InteractiveObject* are kept by *InteractiveContext*, and the *Object* is not destroyed, which results in memory leaks. In general, if the presentation of an interactive object can be computed quickly, it is recommended to *Remove()* it instead of using *Erase()* method.
852 @subsubsection occt_visu_3_4_4 Presentation in the Local Context
854 In open local context, the *Display* functions presented above can be as well.
858 The function *AIS_InteractiveObject::Display* automatically activates the object's default selection mode. When you only want to visualize an Interactive Object in open Context, you must call the function *AIS_InteractiveContext::Display*.
860 You can activate or deactivate specific selection modes in the local open context in several different ways:
861 Use the Display functions with the appropriate modes.
864 AIS_InteractiveContext::ActivateStandardMode
865 //can be used only if a Local Context is opened.
866 AIS_InteractiveContext::DeactivateStandardMode
867 AIS_InteractiveContext::ActivatedStandardModes
868 AIS_InteractiveContext::SetShapeDecomposition
871 This activates the corresponding selection mode for all objects in Local Context, which accept decomposition into sub-shapes. Every new Object which has been loaded into the interactive context and which meets the decomposition criteria is automatically activated according to these modes.
875 If you have opened a local context by loading an object with the default options <i>(AllowShapeDecomposition = Standard_True)</i>, all objects of the "Shape" type are also activated with the same modes. You can change the state of these "Standard" objects by using *SetShapeDecomposition(Status)*.
877 Load an interactive object by the function *AIS_InteractiveContext::Load*.
879 This function allows loading an Interactive Object whether it is visualized or not with a given selection mode, and/or with the necessary decomposition option. If *AllowDecomp=TRUE* and obviously, if the interactive object is of the "Shape" type, these "standard" selection modes will be automatically activated as a function of the modes present in the Local Context.
881 Use *AIS_InteractiveContext::Activate* and *AIS_InteractiveContext::Deactivate* to directly activate/deactivate selection modes on an object.
883 @subsubsection occt_visu_3_4_5 Filters
885 To define an environment of dynamic detection, you can use standard filter classes or create your own.
886 A filter questions the owner of the sensitive primitive in local context to determine if it has the desired qualities. If it answers positively, it is kept. If not, it is rejected.
888 The root class of objects is *SelectMgr_Filter*. The principle behind it is straightforward: a filter tests to see whether the owners <i>(SelectMgr_EntityOwner)</i> detected in mouse position by the Local context selector answer *OK*. If so, it is kept, otherwise it is rejected.
890 You can create a custom class of filter objects by implementing the deferred function *IsOk()*:
893 class MyFilter : public SelectMgr_Filter { };
894 virtual Standard_Boolean MyFilter::IsOk
895 (const Handle(SelectMgr_EntityOwner)& anObj) const = 0;
898 In *SelectMgr*, there are also Composition filters (AND Filters, OR Filters), which allow combining several filters. In InteractiveContext , all filters that you add are stocked in an OR filter (which answers *OK* if at least one filter answers *OK*).
900 There are Standard filters, which have already been implemented in several packages:
901 * *StdSelect_EdgeFilter* - for edges, such as lines and circles;
902 * *StdSelect_FaceFilter* - for faces, such as planes, cylinders and spheres;
903 * *StdSelect_ShapeTypeFilter* - for shape types, such as compounds, solids, shells and wires;
904 * *AIS_TypeFilter* - for types of interactive objects;
905 * *AIS_SignatureFilter* - for types and signatures of interactive objects;
906 * *AIS_AttributeFilter* - for attributes of Interactive Objects, such as color and width.
908 As there are specific behaviors on shapes, each new *Filter* class must, if necessary, redefine *AIS_LocalContext::ActsOn* function, which informs the Local Context if it acts on specific types of sub-shapes. By default, this function answers *FALSE*.
912 Only type filters are activated in Neutral Point to make it possible to identify a specific type of visualized object. For filters to come into play, one or more object selection modes must be activated.
914 There are several functions to manipulate filters:
915 * *AIS_InteractiveContext::AddFilter* adds a filter passed as an argument.
916 * *AIS_InteractiveContext::RemoveFilter* removes a filter passed as an argument.
917 * *AIS_InteractiveContext::RemoveFilters* removes all present filters.
918 * *AIS_InteractiveContext::Filters* gets the list of filters active in a local context.
923 myContext->OpenLocalContext(Standard_False);
924 // no object in neutral point is loaded
926 myContext->ActivateStandardMode(TopAbs_Face);
927 //activates decomposition of shapes into faces.
928 Handle (AIS_Shape) myAIShape = new AIS_Shape ( ATopoShape);
930 myContext->Display(myAIShape,1,-1,Standard_True,Standard_True);
932 //shading visualization mode, no specific mode, authorization for decomposition into sub-shapes. At this Stage, myAIShape is decomposed into faces...
934 Handle(StdSelect_FaceFilter) Fil1= new
935 StdSelect_FaceFilter(StdSelect_Revol);
936 Handle(StdSelect_FaceFilter) Fil2= new
937 StdSelect_FaceFilter(StdSelect_Plane);
939 myContext->AddFilter(Fil1);
940 myContext->AddFilter(Fil2);
942 //only faces of revolution or planar faces will be selected
944 myContext->MoveTo( xpix,ypix,Vue);
945 // detects the mouse position
948 @subsubsection occt_visu_3_4_6 Selection in the Local Context
950 Dynamic detection and selection are put into effect in a straightforward way. There are only a few conventions and functions to be familiar with. The functions are the same in neutral point and in open local context:
951 * *AIS_InteractiveContext::MoveTo* - passes mouse position to Interactive Context selectors
952 * *AIS_InteractiveContext::Select* - stocks what has been detected on the last *MoveTo*. Replaces the previously selected object. Empties the stack if nothing has been detected at the last move
953 * *AIS_InteractiveContext::ShiftSelect* - if the object detected at the last move was not already selected, it is added to the list of the selected objects. If not, it is withdrawn. Nothing happens if you click on an empty area.
954 * *AIS_InteractiveContext::Select* selects everything found in the surrounding area.
955 * *AIS_InteractiveContext::ShiftSelect* selects what was not previously in the list of selected, deselects those already present.
957 Highlighting of detected and selected entities is automatically managed by the Interactive Context, whether you are in neutral point or Local Context. The Highlight colors are those dealt with above. You can nonetheless disconnect this automatic mode if you want to manage this part yourself :
959 AIS_InteractiveContext::SetAutomaticHilight
960 AIS_InteractiveContext::AutomaticHilight
963 If there is no open local context, the objects selected are called **current objects**. If there is a local context, they are called **selected objects**. Iterators allow entities to be recovered in either case. A set of functions allows manipulating the objects, which have been placed in these different lists.
967 When a Local Context is open, you can select entities other than interactive objects (vertices, edges etc.) from decompositions in standard modes, or from activation in specific modes on specific interactive objects. Only interactive objects are stocked in the list of selected objects.
969 You can question the Interactive context by moving the mouse. The following functions can be used:
970 * *AIS_InteractiveContext::HasDetected* informs if something has been detected;
971 * *AIS_InteractiveContext::HasDetectedShape* informs if it is a shape;
972 * *AIS_InteractiveContext::DetectedShape* gets the shape if the detected entity is an object;
973 * *AIS_InteractiveContext::DetectedInteractive* gets the interactive object if the detected entity is an object.
975 After using the *Select* and *ShiftSelect* functions in Neutral Point, you can explore the list of selections, referred to as current objects in this context. The following functions can be used:
976 * *AIS_InteractiveContext::InitCurrent* initiates a scan of this list;
977 * *AIS_InteractiveContext::MoreCurrent* extends the scan;
978 * *AIS_InteractiveContext::NextCurrent* resumes the scan;
979 * *AIS_InteractiveContext::Current* gets the name of the current object detected in the scan;
980 * *AIS_InteractiveContext::FirstCurrentObject* gets the first current interactive object;
981 * *AIS_InteractiveContext::HilightCurrents* highlights current objects;
982 * *AIS_InteractiveContext::UnhilightCurrents* removes highlight from current objects;
983 * *AIS_InteractiveContext::ClearCurrents* empties the list of current objects in order to update it;
984 * *AIS_InteractiveContext::IsCurrent* finds the current object.
986 In the Local Context, you can explore the list of selected objects available. The following functions can be used:
987 * *AIS_InteractiveContext::InitSelected* initiates the list of objects;
988 * *AIS_InteractiveContext::MoreSelected* extends the list of objects;
989 * *AIS_InteractiveContext::NextSelected* resumes a scan;
990 * *AIS_InteractiveContext::SelectedShape* gets the name of the selected object;
991 * *AIS_InteractiveContext::HasSelectedShape* checks if the selected shape is obtained;
992 * *AIS_InteractiveContext::Interactive* gets the picked interactive object;
993 * *AIS_InteractiveContext::HasApplicative* checks if the applicative object has an owner from Interactive attributed to it;
994 * *AIS_InteractiveContext::Applicative* gets the owner of the detected applicative entity;
995 * *AIS_InteractiveContext::IsSelected* gets the name of the selected object.
1000 myAISCtx->InitSelected();
1001 while (myAISCtx->MoreSelected())
1003 if (myAISCtx->HasSelectedShape)
1005 TopoDS_Shape ashape = myAISCtx->SelectedShape();
1006 // to be able to use the picked shape
1010 Handle_AIS_InteractiveObject anyobj = myAISCtx->Interactive();
1011 // to be able to use the picked interactive object
1013 myAISCtx->NextSelected();
1017 You have to ask whether you have selected a shape or an interactive object before you can recover the entity in the Local Context or in the iteration loop. If you have selected a Shape from *TopoDS* on decomposition in standard mode, the *Interactive()* function returns the interactive object, which provided the selected shape. Other functions allow you to manipulate the content of Selected or Current Objects:
1018 * *AIS_InteractiveContext::EraseSelected* erases the selected objects;
1019 * *AIS_InteractiveContext::DisplaySelected* displays them;
1020 * *AIS_InteractiveContext::SetSelected* puts the objects in the list of selections;
1021 * *AIS_InteractiveContext::SetSelectedCurrent* takes the list of selected objects from a local context and puts it into the list of current objects in Neutral Point;
1022 * *AIS_InteractiveContext::AddOrRemoveSelected* adds or removes an object from the list of selected entities;
1023 * *AIS_InteractiveContext::HilightSelected* highlights the selected object;
1024 * *AIS_InteractiveContext::UnhilightSelected* removes highlighting from the selected object;
1025 * *AIS_InteractiveContext::ClearSelected* empties the list of selected objects.
1028 You can highlight and remove highlighting from a current object, and empty the list of current objects using the following functions:
1030 AIS_InteractiveContext::HilightCurrents
1031 AIS_InteractiveContext::UnhilightCurrents
1032 AIS_InteractiveContext::ClearCurrents
1034 When you are in an open Local Context, you may need to keep "temporary" interactive objects. This is possible using the following functions:
1035 * *AIS_InteractiveContext::KeepTemporary* transfers the characteristics of the interactive object seen in its local context (visualization mode, etc.) to the neutral point. When the local context is closed, the object does not disappear.
1036 * *AIS_InteractiveContext::SetSelectedCurrent* allows the selected object to become the current object when you close the local context.
1038 You can also want to use function *AIS_InteractiveContext::ClearLocalContext* to modify in a general way the state of the local context before continuing a selection (emptying objects, removing filters, standard activation modes).
1040 @subsubsection occt_visu_3_4_7 Recommendations
1042 The possibilities of use for local contexts are numerous depending on the type of operation that you want to perform:
1043 * working on all visualized interactive objects,
1044 * working on only a few objects,
1045 * working on a single object.
1047 When you want to work on one type of entity, you should open a local context with the option *UseDisplayedObjects* set to FALSE. Some functions which allow you to recover the visualized interactive objects, which have a given Type, and Signature from the "Neutral Point" are:
1050 AIS_InteractiveContext::DisplayedObjects (AIS_ListOfInteractive& aListOfIO) const;
1051 AIS_InteractiveContext::DisplayedObjects (const AIS_KindOfInteractive WhichKind, const Standard_Integer WhichSignature;
1052 AIS_ListOfInteractive& aListOfIO) const;
1055 At this stage, you only have to load the functions *Load, Activate,* and so on.
1057 When you open a Local Context with default options, you must keep the following points in mind:
1058 * The Interactive Objects visualized at Neutral Point are activated with their default selection mode. You must deactivate those, which you do not want to use.
1059 * The Shape Type Interactive Objects are automatically decomposed into sub-shapes when standard activation modes are launched.
1060 * The "temporary" Interactive Objects present in the Local Contexts are not automatically taken into account. You have to load them manually if you want to use them.
1062 The stages could be the following:
1063 1. Open a Local Context with the right options;
1064 2. Load/Visualize the required complementary objects with the desired activation modes.
1065 3. Activate Standard modes if necessary
1066 4. Create its filters and add them to the Local Context
1067 5. Detect/Select/recover the desired entities
1068 6. Close the Local Context with the adequate index.
1070 It is useful to create an **interactive editor**, to which you pass the Interactive Context. This allow setting up different contexts of selection/presentation according to the operation, which you want to perform.
1072 Let us assume that you have visualized several types of interactive objects: *AIS_Points*, *AIS_Axes*, *AIS_Trihedrons*, and *AIS_Shapes*.
1074 For your applicative function, you need an axis to create a revolved object. You could obtain this axis by identifying:
1075 * an axis which is already visualized,
1077 * a rectilinear edge on the shapes which are present,
1078 * a cylindrical face on the shapes (You will take the axis of this face)
1081 myIHMEditor::myIHMEditor
1082 (const Handle(AIS_InteractiveContext)& Ctx,
1089 myIHMEditor::PrepareContext()
1091 myIndex =myCtx->OpenLocalContext();
1095 Handle(AIS_SignatureFilter) F1 = new AIS_SignatureFilter(AIS_KOI_Datum,AIS_SD_Point);
1096 //filter on the points
1098 Handle(AIS_SignatureFilter) F2 = new AIS_SignatureFilter(AIS_KOI_Datum,AIS_SD_Axis);
1099 //filters on the axes.
1101 Handle(StdSelect_FaceFilter) F3 = new StdSelect_FaceFilter(AIS_Cylinder);
1102 //cylindrical face filters
1104 // activation of standard modes on the shapes..
1105 myCtx->ActivateStandardMode(TopAbs_FACE);
1106 myCtx->ActivateStandardMode(TopAbs_VERTEX);
1111 // at this point, you can call the selection/detection function
1114 void myIHMEditor::MoveTo(xpix,ypix,Vue)
1116 { myCTX->MoveTo(xpix,ypix,vue);
1117 // the highlight of what is detected is automatic.
1119 Standard_Boolean myIHMEditor::Select()
1121 // returns true if you should continue the selection
1123 myCTX->InitSelected();
1124 if(myCTX->MoreSelected())
1126 if(myCTX->HasSelectedShape())
1127 { const TopoDS_Shape& sh = myCTX->SelectedShape();
1131 //if it is the first vertex, you stock it, then you deactivate the faces and only keep the filter on the points:
1133 myCtx->RemoveFilters();
1134 myCTX->DeactivateStandardMode(TopAbs_FACE);
1136 // the filter on the AIS_Points
1137 myFirstV = Standard_False;
1138 return Standard_True;
1143 // construction of the axis return Standard_False;
1148 //it is a cylindrical face : you recover the axis; visualize it; and stock it.
1149 return Standard_False;
1152 // it is not a shape but is no doubt a point.
1155 Handle(AIS_InteractiveObject)
1156 SelObj = myCTX->SelectedInteractive();
1157 if(SelObj->Type()==AIS_KOI_Datum)
1159 if(SelObj->Signature()==1)
1164 return Standard_True;
1169 //construction of the axis, visualization, stocking
1170 return Standard_False;
1176 // you have selected an axis; stock the axis
1177 return Standard_False;
1183 void myIHMEditor::Terminate()
1185 myCtx->CloseLocalContext(myIndex);
1190 @subsection occt_visu_3_5 Standard Interactive Object Classes
1192 Interactive Objects are selectable and viewable objects connecting graphic representation and the underlying reference geometry.
1194 They are divided into four types:
1195 * the **Datum** - a construction geometric element;
1196 * the **Relation** - a constraint on the interactive shape and the corresponding reference geometry;
1197 * the **Object** - a topological shape or connection between shapes;
1198 * **None** a token, that instead of eliminating the object, tells the application to look further until it finds an acceptable object definition in its generation.
1200 Inside these categories, there is a possibility of additional characterization by means of a signature. The signature provides an index to the further characterization. By default, the **Interactive Object** has a *None* type and a signature of 0 (equivalent to *None*).
1201 If you want to give a particular type and signature to your interactive object, you must redefine the two virtual methods: <i>Type</i> and <i>Signature</i>.
1203 @subsubsection occt_visu_3_5_1 Datum
1205 The **Datum** groups together the construction elements such as lines, circles, points, trihedrons, plane trihedrons, planes and axes.
1207 *AIS_Point, AIS_Axis, AIS_Line, AIS_Circle, AIS_Plane* and *AIS_Trihedron* have four selection modes:
1208 * mode 0 : selection of a trihedron;
1209 * mode 1 : selection of the origin of the trihedron;
1210 * mode 2 : selection of the axes;
1211 * mode 3 : selection of the planes XOY, YOZ, XOZ.
1213 when you activate one of modes: 1 2 3 4, you pick AIS objects of type:
1215 * *AIS_Axis* (and information on the type of axis)
1216 * *AIS_Plane* (and information on the type of plane).
1218 *AIS_PlaneTrihedron* offers three selection modes:
1219 * mode 0 : selection of the whole trihedron;
1220 * mode 1 : selection of the origin of the trihedron;
1221 * mode 2 : selection of the axes - same remarks as for the Trihedron.
1223 For the presentation of planes and trihedra, the default unit of length is millimeter, and the default value for the representation of axes is 100. If you modify these dimensions, you must temporarily recover the object **Drawer**. From it, take the *Aspects* in which the values for length are stored (*PlaneAspect* for the plane, *FirstAxisAspect* for trihedra), and change these values inside these Aspects. Finally, recalculate the presentation.
1225 @subsubsection occt_visu_3_5_2 Object
1227 The **Object** type includes topological shapes, and connections between shapes.
1229 *AIS_Shape* has three visualization modes :
1230 * mode 0 : Line (default mode)
1231 * mode 1 : Shading (depending on the type of shape)
1232 * mode 2 : Bounding Box
1234 And at maximum seven selection modes, depending on the shape complexity:
1235 * mode 0 : selection of the *AIS_Shape*;
1236 * mode 1 : selection of the vertices;
1237 * mode 2 : selection of the edges;
1238 * mode 3 : selection of the wires;
1239 * mode 4 : selection of the faces;
1240 * mode 5 : selection of the shells;
1241 * mode 6 : selection of the constituent solids.
1243 * *AIS_Triangulation* is a simple interactive object for displaying triangular mesh contained in *Poly_Triangulation* container.
1244 * *AIS_ConnectedInteractive* is an Interactive Object connecting to another interactive object reference, and located elsewhere in the viewer makes it possible not to calculate presentation and selection, but to deduce them from your object reference.
1245 * *AIS_ConnectedShape* is an object connected to interactive objects having a shape; this class has the same decompositions as *AIS_Shape*. Furthermore, it allows a presentation of hidden parts, which are calculated automatically from the shape of its reference.
1246 * *AIS_MultipleConnectedInteractive* is an object connected to a list of interactive objects (which can also be Connected objects. It does not require memory hungry calculations of presentation)
1247 * *AIS_MultipleConnectedShape* is an interactive Object connected to a list of interactive objects having a Shape <i>(AIS_Shape, AIS_ConnectedShape, AIS_MultipleConnectedShape)</i>. The presentation of hidden parts is calculated automatically.
1248 * *AIS_TexturedShape* is an Interactive Object that supports texture mapping. It is constructed as a usual AIS_Shape, but has additional methods that allow to map a texture on it.
1249 * *MeshVS_Mesh* is an Interactive Object that represents meshes, it has a data source that provides geometrical information (nodes, elements) and can be built up from the source data with a custom presentation builder.
1252 The class *AIS_ColoredShape* allows using custom colors and line widths for *TopoDS_Shape* objects and their sub-shapes.
1255 AIS_ColoredShape aColoredShape = new AIS_ColoredShape (theShape);
1257 // setup color of entire shape
1258 aColoredShape->SetColor (Quantity_Color (Quantity_NOC_RED));
1260 // setup line width of entire shape
1261 aColoredShape->SetWidth (1.0);
1263 // set transparency value
1264 aColoredShape->SetTransparency (0.5);
1266 // customize color of specified sub-shape
1267 aColoredShape->SetCustomColor (theSubShape, Quantity_Color (Quantity_NOC_BLUE1));
1269 // customize line width of specified sub-shape
1270 aColoredShape->SetCustomWidth (theSubShape, 0.25);
1273 The presentation class *AIS_PointCloud* can be used for efficient drawing of large arbitrary sets of colored points. It uses *Graphic3d_ArrayOfPoints* to pass point data into OpenGl graphic driver to draw a set points as an array of "point sprites". The point data is packed into vertex buffer object for performance.
1274 - The type of point marker used to draw points can be specified as a presentation aspect.
1275 - The presentation provides selection by a bounding box of the visualized set of points. It supports two display / highlighting modes: points or bounding box.
1277 @image html point_cloud.png "A random colored cloud of points"
1281 Handle(Graphic3d_ArrayOfPoints) aPoints = new Graphic3d_ArrayOfPoints (2000, Standard_True);
1282 aPoints->AddVertex (gp_Pnt(-40.0, -40.0, -40.0), Quantity_Color (Quantity_NOC_BLUE1));
1283 aPoints->AddVertex (gp_Pnt (40.0, 40.0, 40.0), Quantity_Color (Quantity_NOC_BLUE2));
1285 Handle(AIS_PointCloud) aPntCloud = new AIS_PointCloud();
1286 aPntCloud->SetPoints (aPoints);
1289 The draw command *vpointcloud* builds a cloud of points from shape triangulation.
1290 This command can also draw a sphere surface or a volume with a large amount of points (more than one million).
1293 @subsubsection occt_visu_3_5_3 Relations
1295 The **Relation** is made up of constraints on one or more interactive shapes and the corresponding reference geometry. For example, you might want to constrain two edges in a parallel relation. This constraint is considered as an object in its own right, and is shown as a sensitive primitive. This takes the graphic form of a perpendicular arrow marked with the || symbol and lying between the two edges.
1297 The following relations are provided by *AIS*:
1298 * *AIS_ConcentricRelation*
1300 * *AIS_IdenticRelation*
1301 * *AIS_ParallelRelation*
1302 * *AIS_PerpendicularRelation*
1304 * *AIS_SymmetricRelation*
1305 * *AIS_TangentRelation*
1307 The list of relations is not exhaustive.
1309 @subsubsection occt_visu_3_5_4 Dimensions
1310 * *AIS_AngleDimension*
1311 * *AIS_Chamf3dDimension*
1312 * *AIS_DiameterDimension*
1313 * *AIS_DimensionOwner*
1314 * *AIS_LengthDimension*
1315 * *AIS_OffsetDimension*
1316 * *AIS_RadiusDimension*
1318 @subsubsection occt_visu_3_5_5 MeshVS_Mesh
1320 *MeshVS_Mesh* is an Interactive Object that represents meshes. This object differs from the *AIS_Shape* as its geometrical data is supported by the data source *MeshVS_DataSource* that describes nodes and elements of the object. As a result, you can provide your own data source.
1322 However, the *DataSource* does not provide any information on attributes, for example nodal colors, but you can apply them in a special way - by choosing the appropriate presentation builder.
1324 The presentations of *MeshVS_Mesh* are built with the presentation builders *MeshVS_PrsBuilder*. You can choose between the builders to represent the object in a different way. Moreover, you can redefine the base builder class and provide your own presentation builder.
1326 You can add/remove builders using the following methods:
1328 MeshVS_Mesh::AddBuilder (const Handle (MeshVS_PrsBuilder) &Builder, Standard_Boolean TreatAsHilighter)
1329 MeshVS_Mesh::RemoveBuilder (const Standard_Integer Index)
1330 MeshVS_Mesh::RemoveBuilderById (const Standard_Integer Id)
1333 There is a set of reserved display and highlighting mode flags for *MeshVS_Mesh*. Mode value is a number of bits that allows selecting additional display parameters and combining the following mode flags, which allow displaying mesh in wireframe, shading and shrink modes:
1335 MeshVS_DMF_WireFrame
1340 It is also possible to display deformed mesh in wireframe, shading or shrink modes usung :
1342 MeshVS_DMF_DeformedPrsWireFrame
1343 MeshVS_DMF_DeformedPrsShading
1344 MeshVS_DMF_DeformedPrsShrink
1347 The following methods represent different kinds of data :
1349 MeshVS_DMF_VectorDataPrs
1350 MeshVS_DMF_NodalColorDataPrs
1351 MeshVS_DMF_ElementalColorDataPrs
1352 MeshVS_DMF_TextDataPrs
1353 MeshVS_DMF_EntitiesWithData
1356 The following methods provide selection and highlighting :
1358 MeshVS_DMF_SelectionPrs
1359 MeshVS_DMF_HilightPrs
1362 *MeshVS_DMF_User* is a user-defined mode.
1364 These values will be used by the presentation builder.
1365 There is also a set of selection modes flags that can be grouped in a combination of bits:
1369 * *MeshVS_SMF_Volume*
1370 * *MeshVS_SMF_Element* - groups *0D, Link, Face* and *Volume* as a bit mask ;
1372 * *MeshVS_SMF_All* - groups *Element* and *Node* as a bit mask;
1374 * *MeshVS_SMF_Group*
1376 Such an object, for example, can be used for displaying the object and stored in the STL file format:
1379 // read the data and create a data source
1380 Handle (StlMesh_Mesh) aSTLMesh = RWStl::ReadFile (aFileName);
1381 Handle (XSDRAWSTLVRML_DataSource) aDataSource = new XSDRAWSTLVRML_DataSource (aSTLMesh);
1384 Handle (MeshVS_Mesh) aMesh = new MeshVS();
1385 aMesh->SetDataSource (aDataSource);
1387 // use default presentation builder
1388 Handle (MeshVS_MeshPrsBuilder) aBuilder = new MeshVS_MeshPrsBuilder (aMesh);
1389 aMesh->AddBuilder (aBuilder, Standard_True);
1392 *MeshVS_NodalColorPrsBuilder* allows representing a mesh with a color scaled texture mapped on it.
1393 To do this you should define a color map for the color scale, pass this map to the presentation builder,
1394 and define an appropriate value in the range of 0.0 - 1.0 for every node.
1396 The following example demonstrates how you can do this (check if the view has been set up to display textures):
1399 // assign nodal builder to the mesh
1400 Handle (MeshVS_NodalColorPrsBuilder) aBuilder = new MeshVS_NodalColorPrsBuilder
1401 (aMesh,MeshVS_DMF_NodalColorDataPrs | MeshVS_DMF_OCCMask);
1402 aBuilder->UseTexture (Standard_True);
1404 // prepare color map
1405 Aspect_SequenceOfColor aColorMap;
1406 aColorMap.Append ((Quantity_NameOfColor) Quantity_NOC_RED);
1407 aColorMap.Append ((Quantity_NameOfColor) Quantity_NOC_BLUE1);
1409 // assign color scale map values (0..1) to nodes
1410 TColStd_DataMapOfIntegerReal aScaleMap;
1412 // iterate through the nodes and add an node id and an appropriate value to the map
1413 aScaleMap.Bind (anId, aValue);
1415 // pass color map and color scale values to the builder
1416 aBuilder->SetColorMap (aColorMap);
1417 aBuilder->SetInvalidColor (Quantity_NOC_BLACK);
1418 aBuilder->SetTextureCoords (aScaleMap);
1419 aMesh->AddBuilder (aBuilder, Standard_True);
1422 @subsection occt_visu_3_6 Dynamic Selection
1424 The idea of dynamic selection is to represent the entities, which you want to select by a bounding box in the actual 2D space of the selection view. The set of these zones is ordered by a powerful sorting algorithm.
1425 To then find the applicative entities actually detected at this position, all you have to do is read which rectangles are touched at mouse position (X,Y) of the view, and judiciously reject some of the entities which have provided these rectangles.
1427 @subsubsection occt_visu_3_6_1 How to go from the objects to 2D boxes
1430 An intermediary stage consists in representing what you can make selectable by means of sensitive primitives and owners, entities of a high enough level to be known by the selector mechanisms.
1432 The sensitive primitive is capable of:
1433 * giving a 2D bounding box to the selector.
1434 * answering the rejection criteria positively or negatively by a "Matches" function.
1435 * being projected from 3D in the 2D space of the view if need be.
1436 * returning the owner which it will represent in terms of selection.
1438 A set of standard sensitive primitives exists in Select3D packages for 3D primitives.
1440 The owner is the entity, which makes it possible to link the sensitive primitives and the objects that you really wanted to detect. It stocks the diverse information, which makes it possible to find objects. An owner has a priority (*5* by default), which you can change to make one entity more selectable than another.
1442 @image html visualization_image021.png
1443 @image latex visualization_image021.png
1445 @subsubsection occt_visu_3_6_2 Implementation in an interactive/selectable object
1447 Define the number of selection modes possible, i.e. what you want to identify by activating each of the selection modes.
1449 For example: for an interactive object representing a topological shape:
1450 * mode 0: selection of the interactive object itself;
1451 * mode 1: selection of the vertices;
1452 * mode 2: selection of the edges;
1453 * mode 3: selection of the wires;
1454 * mode 4: selection of the detectable faces.
1456 For each selection mode of an interactive object, "model" is the set of entities, which you want to locate by these primitives and these owners.
1458 There is an "owner" root class, *SelectMgr_EntityOwner*, containing a reference to a selectable object, which has created it. If you want to stock its information, you have to create classes derived from this root class. Example: for shapes, there is the *StdSelect_BRepOwner* class, which can save a *TopoDS* shape as a field as well as the Interactive Object.
1460 The set of sensitive primitives which has been calculated for a given mode is stocked in *SelectMgr_Selection*.
1462 For an Interactive object, the modeling is done in the *ComputeSelection* virtual function.
1464 Let us consider an example of an interactive object representing a box.
1466 We are interested in two location modes:
1467 * mode 0: location of the whole box.
1468 * mode 1: location of the edges on the box.
1470 For the first mode, all sensitive primitives will have the same owner, which will represent the interactive object. In the second case, we have to create an owner for each edge, and this owner will have to contain the index for the edge, which it represents. You will create a class of owner, which derives from *SelectMgr_EntityOwner*.
1472 The *ComputeSelection* function for the interactive box can have the following form:
1475 void InteractiveBox::ComputeSelection
1476 (const Handle(SelectMgr_Selection)& Sel,
1477 const Standard_Integer Mode)
1480 { case 0: //locating the whole box by making its faces sensitive...
1482 Handle(SelectMgr_EntityOwner) Ownr = new SelectMgr_EntityOwner(this,5);
1483 for(Standard_Integer I=1;I<=Nbfaces;I++)
1485 //Array is a TColgp_Array1OfPnt: which represents the array of vertices. Sensitivity is
1486 Select3D_TypeOfSensitivity value
1487 Sel->Add(new Select3D_SensitiveFace(Ownr,Array,Sensitivity));
1492 // locates the edges {
1493 for(Standard_Integer i=1;i<=12;i++)
1495 // 1 owner per edge...
1496 Handle(mypk_EdgeOwner) Ownr = new mypk_EdgeOwner(this,i,6);
1498 Sel->Add(new Select3D_SensitiveSegment (Ownr,firstpt(i),lastpt(i)));
1506 Selectable objects are loaded in the selection manager, which has one or more selectors; in general, we suggest assigning one selector per viewer. All you have to do afterwards is to activate or deactivate the different selection modes for selectable objects. The *SelectionManager* looks after the call to the *ComputeSelection* functions for different objects.
1508 NOTE: This procedure is completely hidden if you use the <a href="#occt_visu_3_3"> AIS Interactive Context </a>
1512 //We have several " interactive boxes " box1, box2, box3;
1513 Handle(SelectMgr_SelectionManager) SM = new SelectMgr_SelectionManager();
1514 Handle(StdSelect_ViewerSelector3d) VS = new StdSelect_ViewerSelector3d();
1516 SM->Load(box1);SM->Load(box2);SM->Load(box3);
1518 SM->Activate(box1,0,VS);
1519 // activates mode 0 of box 1 in the selector VS
1520 SM->Activate(box1,1,VS);
1521 M->Activate(box3,1,VS);
1522 VS->Pick(xpix,ypix,vue3d)
1523 // detection of primitives by mouse position.
1524 Handle(EntityOwner) POwnr = VS->OnePicked();
1525 // picking of the "best" owner detected
1526 for(VS->Init();VS->More();VS->Next())
1529 // picking of all owners detected
1531 SM->Deactivate(box1);
1532 // deactivate all active modes of box1
1535 @section occt_visu_4 3D Presentations
1537 @subsection occt_visu_4_1 Glossary of 3D terms
1539 * **Anti-aliasing** This mode attempts to improve the screen resolution by drawing lines and curves in a mixture of colors so that to the human eye the line or curve is smooth. The quality of the result is linked to the quality of the algorithm used by the workstation hardware.
1540 * **Depth-cueing** Reduces the color intensity for the portion of an object further away from the eye to give the impression of depth. This is used for wireframe objects. Shaded objects do not require this.
1541 * **Group** - a set of primitives and attributes on those primitives. Primitives and attributes may be added to a group but cannot be removed from a group, except by erasing them globally. A group can have a pick identity.
1542 * **Light** There are five kinds of light source - ambient, headlight, directional, positional and spot. The light is only activated in a shading context in a view.
1543 * **Primitive** - a drawable element. It has a definition in 3D space. Primitives can either be lines, faces, text, or markers. Once displayed markers and text remain the same size. Lines and faces can be modified e.g. zoomed. Primitives must be stored in a group.
1544 * **Structure** - manages a set of groups. The groups are mutually exclusive. A structure can be edited, adding or removing groups. A structure can reference other structures to form a hierarchy. It has a default (identity) transformation and other transformations may be applied to it (rotation, translation, scale, etc). It has no default attributes for the primitive lines, faces, markers, and text. Attributes may be set in a structure but they are overridden by the attributes in each group. Each structure has a display priority associated with it, which rules the order in which it is redrawn in a 3D viewer. If the visualization mode is incompatible with the view it is not displayed in that view, e.g. a shading-only object is not visualized in a wireframe view.
1545 * **View** - is defined by a view orientation, a view mapping, and a context view.
1546 * **Viewer** - manages a set of views.
1547 * **View orientation** - defines the manner in which the observer looks at the scene in terms of View Reference Coordinates.
1548 * **View mapping** - defines the transformation from View Reference Coordinates to the Normalized Projection Coordinates. This follows the Phigs scheme.
1549 * **Z-Buffering** -= a form of hidden surface removal in shading mode only. This is always active for a view in the shading mode. It cannot be suppressed.
1551 @subsection occt_visu_4_2 Graphic primitives
1553 The *Graphic3d* package is used to create 3D graphic objects in a 3D viewer. These objects called **structures** are made up of groups of primitives and attributes, such as polylines, planar polygons with or without holes, text and markers, and attributes, such as color, transparency, reflection, line type, line width, and text font. A group is the smallest editable element of a structure. A transformation can be applied to a structure. Structures can be connected to form a tree of structures, composed by transformations. Structures are globally manipulated by the viewer.
1555 Graphic structures can be:
1560 * Connected to form a tree hierarchy of structures, created by transformations.
1562 There are classes for:
1563 * Visual attributes for lines, faces, markers, text, materials,
1564 * Vectors and vertices,
1565 * Graphic objects, groups, and structures.
1567 @subsubsection occt_visu_4_2_2 Structure hierarchies
1569 The root is the top of a structure hierarchy or structure network. The attributes of a parent structure are passed to its descendants. The attributes of the descendant structures do not affect the parent. Recursive structure networks are not supported.
1571 @subsubsection occt_visu_4_2_3 Graphic primitives
1573 * Have one or more vertices,
1574 * Have a type, a scale factor, and a color,
1575 * Have a size, shape, and orientation independent of transformations.
1577 * Have one closed boundary,
1578 * Have at least three vertices,
1579 * Are planar and have a normal,
1580 * Have interior attributes - style, color, front and back material, texture and reflection ratio,
1581 * Have a boundary with the following attributes - type, width scale factor, color. The boundary is only drawn when the interior style is hollow.
1583 * **Polygons with holes**
1584 * Have multiple closed boundaries, each one with at least three vertices,
1585 * Are planar and have a normal,
1586 * Have interior attributes - style, color, front and back material,
1587 * Have a boundary with the following attributes - type, width scale factor, color. The boundary is only drawn when the interior style is hollow.
1590 * Have two or more vertices,
1591 * Have the following attributes - type, width scale factor, color.
1594 * Has geometric and non-geometric attributes,
1595 * Geometric attributes - character height, character up vector, text path, horizontal and vertical alignment, orientation, three-dimensional position, zoomable flag
1596 * Non-geometric attributes - text font, character spacing, character expansion factor, color.
1598 @subsubsection occt_visu_4_2_4 Primitive arrays
1600 Primitive arrays are a more efficient approach to describe and display the primitives from the aspects of memory usage and graphical performance. The key feature of the primitive arrays is that the primitive data is not duplicated. For example, two polygons could share the same vertices, so it is more efficient to keep the vertices in a single array and specify the polygon vertices with indices of this array. In addition to such kind of memory savings, the OpenGl graphics driver provides the Vertex Buffer Objects (VBO). VBO is a sort of video memory storage that can be allocated to hold the primitive arrays, thus making the display operations more efficient and releasing the RAM memory.
1602 The Vertex Buffer Objects are enabled by default, but VBOs availability depends on the implementation of OpenGl. If the VBOs are unavailable or there is not enough video memory to store the primitive arrays, the RAM memory will be used to store the arrays.
1604 The Vertex Buffer Objects can be disabled at the application level. You can use the method *Graphic3d_GraphicDriver::EnableVBO (const Standard_Boolean status)* to enable/disable VBOs:
1606 The following example shows how to disable the VBO support:
1609 // get the graphic driver
1610 Handle (Graphic3d_GraphicDriver) aDriver =
1611 myAISContext->CurrentViewer()->Driver();
1613 // disable VBO support
1614 aDriver->EnableVBO (Standard_False);
1617 **Note** that the use of Vertex Buffer Objects requires the application level primitive data provided by the *Graphic3d_ArrayOfPrimitives* to be transferred to the video memory. *TKOpenGl* transfers the data and releases the *Graphic3d_ArrayOfPrimitives* internal pointers to the primitive data. Thus it might be necessary to pay attention to such kind of behaviour, as the pointers could be modified (nullified) by the *TKOpenGl*.
1619 The different types of primitives could be presented with the following primitive arrays:
1620 * *Graphic3d_ArrayOfPoints,*
1621 * *Graphic3d_ArrayOfPolygons,*
1622 * *Graphic3d_ArrayOfPolylines,*
1623 * *Graphic3d_ArrayOfQuadrangles,*
1624 * *Graphic3d_ArrayOfQuadrangleStrips,*
1625 * *Graphic3d_ArrayOfSegments,*
1626 * *Graphic3d_ArrayOfTriangleFans,*
1627 * *Graphic3d_ArrayOfTriangles,*
1628 * *Graphic3d_ArrayOfTriangleStrips.*
1630 The *Graphic3d_ArrayOfPrimitives* is a base class for these primitive arrays.
1632 Method *Graphic3d_ArrayOfPrimitives::AddVertex* allows adding There is a set of similar methods to add vertices to the primitive array.
1634 These methods take vertex coordinates as an argument and allow you to define the color, the normal and the texture coordinates assigned to the vertex. The return value is the actual number of vertices in the array.
1636 You can also modify the values assigned to the vertex or query these values by the vertex index:
1637 * *void Graphic3d_ArrayOfPrimitives::SetVertice*
1638 * *void Graphic3d_ArrayOfPrimitives::SetVertexColor*
1639 * *void Graphic3d_ArrayOfPrimitives::SetVertexNormal*
1640 * *void Graphic3d_ArrayOfPrimitives::SetVertexTexel*
1641 * *gp_Pnt Graphic3d_ArrayOfPrimitives::Vertices*
1642 * *gp_Dir Graphic3d_ArrayOfPrimitives::VertexNormal*
1643 * *gp_Pnt3d Graphic3d_ArrayOfPrimitives::VertexTexel*
1644 * *Quantity_Color Graphic3d_ArrayOfPrimitives::VertexColor*
1645 * *void Graphic3d_ArrayOfPrimitives::Vertices*
1646 * *void Graphic3d_ArrayOfPrimitives::VertexNormal*
1647 * *void Graphic3d_ArrayOfPrimitives::VertexTexel*
1648 * *void Graphic3d_ArrayOfPrimitives::VertexColor*
1650 The following example shows how to define an array of points:
1654 Handle (Graphic3d_ArrayOfPoints) anArray = new Graphic3d_ArrayOfPoints (aVerticiesMaxCount);
1656 // add vertices to the array
1657 anArray->AddVertex (10.0, 10.0, 10.0);
1658 anArray->AddVertex (0.0, 10.0, 10.0);
1660 // add the array to the structure
1661 Handle (Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (aPrs);
1662 aGroup->BeginPrimitives ();
1663 aGroup->AddPrimitiveArray (anArray);
1664 aGroup->EndPrimitives ();
1667 If the primitives share the same vertices (polygons, triangles, etc.) then you can define them as indices of the vertices array.
1669 The method *Graphic3d_ArrayOfPrimitives::AddEdge* allows defining the primitives by indices. This method adds an "edge" in the range <i> [1, VertexNumber() ] </i> in the array.
1671 It is also possible to query the vertex defined by an edge using method *Graphic3d_ArrayOfPrimitives::Edge*
1673 The following example shows how to define an array of triangles:
1677 Standard_Boolean IsNormals = Standard_False;
1678 Standard_Boolean IsColors = Standard_False;
1679 Standard_Boolean IsTextureCrds = Standard_False;
1680 Handle (Graphic3d_ArrayOfTriangles) anArray =
1681 new Graphic3d_ArrayOfTriangles (aVerticesMaxCount,
1686 // add vertices to the array
1687 anArray->AddVertex (-1.0, 0.0, 0.0); // vertex 1
1688 anArray->AddVertex ( 1.0, 0.0, 0.0); // vertex 2
1689 anArray->AddVertex ( 0.0, 1.0, 0.0); // vertex 3
1690 anArray->AddVertex ( 0.0,-1.0, 0.0); // vertex 4
1692 // add edges to the array
1693 anArray->AddEdge (1); // first triangle
1694 anArray->AddEdge (2);
1695 anArray->AddEdge (3);
1696 anArray->AddEdge (1); // second triangle
1697 anArray->AddEdge (2);
1698 anArray->AddEdge (4);
1700 // add the array to the structure
1701 Handle (Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (aPrs);
1702 aGroup->BeginPrimitives ();
1703 aGroup->AddPrimitiveArray (anArray);
1704 aGroup->EndPrimitives ();
1707 If the primitive array presents primitives built from sequential sets of vertices, for example polygons, then you can specify the bounds, or the number of vertices for each primitive. You can use the method *Graphic3d_ArrayOfPrimitives::AddBound* to define the bounds and the color for each bound. This method returns the actual number of bounds.
1709 It is also possible to set the color and query the number of edges in the bound and bound color.
1711 Standard_Integer Graphic3d_ArrayOfPrimitives::Bound
1712 Quantity_Color Graphic3d_ArrayOfPrimitives::BoundColor
1713 void Graphic3d_ArrayOfPrimitives::BoundColor
1716 The following example shows how to define an array of polygons:
1720 Standard_Boolean IsNormals = Standard_False;
1721 Standard_Boolean IsVertexColors = Standard_False;
1722 Standard_Boolean IsFaceColors = Standard_False;
1723 Standard_Boolean IsTextureCrds = Standard_False;
1724 Handle (Graphic3d_ArrayOfPolygons) anArray =
1725 new Graphic3d_ArrayOfPolygons (aVerticesMaxCount,
1733 // add bounds to the array, first polygon
1734 anArray->AddBound (3);
1735 anArray->AddVertex (-1.0, 0.0, 0.0);
1736 anArray->AddVertex ( 1.0, 0.0, 0.0);
1737 anArray->AddVertex ( 0.0, 1.0, 0.0);
1739 // add bounds to the array, second polygon
1740 anArray->AddBound (4);
1741 anArray->AddVertex (-1.0, 0.0, 0.0);
1742 anArray->AddVertex ( 1.0, 0.0, 0.0);
1743 anArray->AddVertex ( 1.0,-1.0, 0.0);
1744 anArray->AddVertex (-1.0,-1.0, 0.0);
1746 // add the array to the structure
1747 Handle (Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (aPrs);
1748 aGroup->BeginPrimitives ();
1749 aGroup->AddPrimitiveArray (anArray);
1750 aGroup->EndPrimitives ();
1753 There are also several helper methods. You can get the type of the primitive array:
1755 Graphic3d_TypeOfPrimitiveArray
1756 Graphic3d_ArrayOfPrimitives::Type
1757 Standard_CString Graphic3d_ArrayOfPrimitives::StringType
1760 and check if the primitive array provides normals, vertex colors and vertex texels (texture coordinates):
1763 Standard_Boolean Graphic3d_ArrayOfPrimitives::HasVertexNormals
1764 Standard_Boolean Graphic3d_ArrayOfPrimitives::HasVertexColors
1765 Standard_Boolean Graphic3d_ArrayOfPrimitives::HasVertexTexels
1767 or get the number of vertices, edges and bounds:
1769 Standard_Integer Graphic3d_ArrayOfPrimitives::VertexNumber
1770 Standard_Integer Graphic3d_ArrayOfPrimitives::EdgeNumber
1771 Standard_Integer Graphic3d_ArrayOfPrimitives::BoundNumber
1774 @subsubsection occt_visu_4_2_5 Text primitive
1776 The OpenGl graphics driver uses advanced text rendering powered by FTGL library. This library provides vector text rendering, as a result the text can be rotated and zoomed without quality loss.
1777 *Graphic3d* text primitives have the following features:
1778 * fixed size (non-zoomable) or zoomable,
1779 * can be rotated to any angle in the view plane,
1780 * support unicode charset.
1782 The text attributes for the group could be defined with the *Graphic3d_AspectText3d* attributes group.
1783 To add any text to the graphic structure you can use the following methods:
1785 void Graphic3d_Group::Text
1786 (const Standard_CString AText,
1787 const Graphic3d_Vertex& APoint,
1788 const Standard_Real AHeight,
1789 const Quantity_PlaneAngle AAngle,
1790 const Graphic3d_TextPath ATp,
1791 const Graphic3d_HorizontalTextAlignment AHta,
1792 const Graphic3d_VerticalTextAlignment AVta,
1793 const Standard_Boolean EvalMinMax),
1795 *AText* parameter is the text string, *APoint* is the three-dimensional position of the text, *AHeight* is the text height, *AAngle* is the orientation of the text (at the moment, this parameter has no effect, but you can specify the text orientation through the *Graphic3d_AspectText3d* attributes).
1797 *ATp* parameter defines the text path, *AHta* is the horizontal alignment of the text, *AVta* is the vertical alignment of the text.
1799 You can pass *Standard_False* as *EvalMinMax* if you do not want the graphic3d structure boundaries to be affected by the text position.
1801 **Note** that the text orientation angle can be defined by *Graphic3d_AspectText3d* attributes.
1803 void Graphic3d_Group::Text
1804 (const Standard_CString AText,
1805 const Graphic3d_Vertex& APoint,
1806 const Standard_Real AHeight,
1807 const Standard_Boolean EvalMinMax)
1808 void Graphic3d_Group::Text
1809 (const TCcollection_ExtendedString &AText,
1810 const Graphic3d_Vertex& APoint,
1811 const Standard_Real AHeight,
1812 const Quantity_PlaneAngle AAngle,
1813 const Graphic3d_TextPath ATp,
1814 const Graphic3d_HorizontalTextAlignment AHta,
1815 const Graphic3d_VerticalTextAlignment AVta,
1816 const Standard_Boolean EvalMinMax)
1817 void Graphic3d_Group::Text
1818 (const TCcollection_ExtendedString &AText,
1819 const Graphic3d_Vertex& APoint,
1820 const Standard_Real AHeight,
1821 const Standard_Boolean EvalMinMax)
1827 Handle (Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (aPrs);
1829 // change the text aspect
1830 Handle(Graphic3d_AspectText3d) aTextAspect = new Graphic3d_AspectText3d ();
1831 aTextAspect->SetTextZoomable (Standard_True);
1832 aTextAspect->SetTextAngle (45.0);
1833 aGroup->SetPrimitivesAspect (aTextAspect);
1835 // add a text primitive to the structure
1836 Graphic3d_Vertex aPoint (1, 1, 1);
1837 aGroup->Text (Standard_CString ("Text"), aPoint, 16.0);
1840 @subsubsection occt_visu_4_2_6 Materials
1842 A *Graphic3d_MaterialAspect* is defined by:
1844 * Diffuse reflection - a component of the object color;
1845 * Ambient reflection;
1846 * Specular reflection - a component of the color of the light source;
1849 The following items are required to determine the three colors of reflection:
1851 * Coefficient of diffuse reflection;
1852 * Coefficient of ambient reflection;
1853 * Coefficient of specular reflection.
1855 @subsubsection occt_visu_4_2_7 Textures
1857 A *texture* is defined by a name.
1858 Three types of texture are available:
1861 * Environment mapping.
1863 @subsubsection occt_visu_4_2_8 Shaders
1865 OCCT visualization core supports GLSL shaders. Currently OCCT supports only vertex and fragment GLSL shader. Shaders can be assigned to a generic presentation by its drawer attributes (Graphic3d aspects). To enable custom shader for a specific AISShape in your application, the following API functions are used:
1868 // Create shader program
1869 Handle(Graphic3d_ShaderProgram) aProgram = new Graphic3d_ShaderProgram();
1871 // Attach vertex shader
1872 aProgram->AttachShader (Graphic3d_ShaderObject::CreateFromFile(
1873 Graphic3d_TOS_VERTEX, "<Path to VS>"));
1875 // Attach fragment shader
1876 aProgram->AttachShader (Graphic3d_ShaderObject::CreateFromFile(
1877 Graphic3d_TOS_FRAGMENT, "<Path to FS>"));
1879 // Set values for custom uniform variables (if they are)
1880 aProgram->PushVariable ("MyColor", Graphic3d_Vec3(0.0f, 1.0f, 0.0f));
1882 // Set aspect property for specific AISShape
1883 theAISShape->Attributes()->ShadingAspect()->Aspect()->SetShaderProgram (aProgram);
1886 @subsection occt_visu_4_3 Graphic attributes
1888 @subsubsection occt_visu_4_3_1 Aspect package overview
1890 The *Aspect* package provides classes for the graphic elements in the viewer:
1891 * Groups of graphic attributes;
1892 * Edges, lines, background;
1895 * Enumerations for many of the above.
1897 @subsection occt_visu_4_4 3D view facilities
1899 @subsubsection occt_visu_4_4_1 Overview
1901 The *V3d* package provides the resources to define a 3D viewer and the views attached to this viewer (orthographic, perspective). This package provides the commands to manipulate the graphic scene of any 3D object visualized in a view on screen.
1903 A set of high-level commands allows the separate manipulation of parameters and the result of a projection (Rotations, Zoom, Panning, etc.) as well as the visualization attributes (Mode, Lighting, Clipping, Depth-cueing, etc.) in any particular view.
1905 The *V3d* package is basically a set of tools directed by commands from the viewer front-end. This tool set contains methods for creating and editing classes of the viewer such as:
1906 * Default parameters of the viewer,
1907 * Views (orthographic, perspective),
1908 * Lighting (positional, directional, ambient, spot, headlight),
1909 * Clipping planes (note that only Z-clipping planes can work with the Phigs interface),
1910 * Instantiated sequences of views, planes, light sources, graphic structures, and picks,
1911 * Various package methods.
1913 @subsubsection occt_visu_4_4_2 A programming example
1915 This sample TEST program for the *V3d* Package uses primary packages *Xw* and *Graphic3d* and secondary packages *Visual3d, Aspect, Quantity, Phigs* and *math*.
1918 //Create a default display connection
1919 Handle(Aspect_DisplayConnection) aDisplayConnection = new Aspect_DisplayConnection();
1921 //Create a Graphic Driver from the default Aspect_DisplayConnection
1922 Handle(OpenGl_GraphicDriver) GD = new OpenGl_GraphicDriver (aDisplayConnection);
1924 //Create a Viewer to this Driver
1925 Handle(V3d_Viewer) VM = new V3d_Viewer(GD, 400.,
1928 // Default projection
1929 Quantity_NOC_DARKVIOLET,
1930 // Default background
1932 // Type of visualization
1937 // Create a structure in this Viewer
1938 Handle(Graphic3d_Structure) S = new Graphic3d_Structure(VM->Viewer()) ;
1940 // Type of structure
1941 S->SetVisual (Graphic3d_TOS_SHADING);
1943 // Create a group of primitives in this structure
1944 Handle(Graphic3d_Group) G = new Graphic3d_Group(S) ;
1946 // Fill this group with one polygon of size 100
1947 Graphic3d_Array1OfVertex Points(0,3) ;
1948 Points(0).SetCoord(-100./2.,-100./2.,-100./2.) ;
1949 Points(1).SetCoord(-100./2., 100./2.,-100./2.) ;
1950 Points(2).SetCoord( 100./2., 100./2.,-100./2.) ;
1951 Points(3).SetCoord( 100./2.,-100./2.,-100./2.) ;
1952 Normal.SetCoord(0.,0.,1.) ;
1953 G->Polygon(Points,Normal) ;
1955 // Create Ambient and Infinite Lights in this Viewer
1956 Handle(V3d_AmbientLight) L1 = new V3d_AmbientLight
1957 (VM,Quantity_NOC_GRAY50) ;
1958 Handle(V3d_DirectionalLight) L2 = new V3d_DirectionalLight
1959 (VM,V3d_XnegYnegZneg,Quantity_NOC_WHITE) ;
1961 // Create a 3D quality Window with the same DisplayConnection
1962 Handle(Xw_Window) W = new Xw_Window(aDisplayConnection,"Test V3d",0.5,0.5,0.5,0.5) ;
1964 // Map this Window to this screen
1967 // Create a Perspective View in this Viewer
1968 Handle(V3d_View) aView = new V3d_View(VM);
1969 aView->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Perspective);
1970 // Associate this View with the Window
1971 aView ->SetWindow(W);
1972 // Display ALL structures in this View
1973 VM->Viewer()->Display();
1974 // Finally update the Visualization in this View
1978 As an alternative to manual setting of perspective parameters the V3d_View::ZfitAll() and V3d_View::FitAll() functions can be used:
1981 // Display shape in Viewer VM
1982 Handle(AIS_InteractiveContext) aContext = new AIS_InteractiveContext (VM);
1983 aContext->Display(shape);
1984 // Create a Perspective View in Viewer VM
1985 Handle(V3d_View) V = new V3d_View (VM);
1986 aview->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Perspective);
1987 // Change Z-min and Z-max planes of projection volume to match the displayed objects
1989 // Fit view to object size
1993 @subsubsection occt_visu_4_4_3 Define viewing parameters
1995 View projection and orientation in OCCT *v3d* view are driven by camera. The camera calculates and supplies projection and view orientation matrices for rendering by OpenGL. The allows to the user to control all projection parameters. The camera is defined by the following properties:
1997 * **Eye** - Defines the observer (camera) position. Make sure the Eye point never gets between the Front and Back clipping planes.
1999 * **Center** - defines the origin of View Reference Coordinates (where camera is aimed at).
2001 * **Direction** - defines the direction of camera view (from the Eye to the Center).
2003 * **Distance** - defines the distance between the Eye and the Center.
2005 * **Front** Plane - Defines the position of the front clipping plane in View Reference Coordinates system.
2007 * **Back** Plane - Defines the position of the back clipping plane in View Reference Coordinates system.
2009 * **ZNear** - defines the distance between the Eye and the Front plane.
2011 * **ZFar** - defines the distance between the Eye and the Back plane.
2013 Most common view manipulations (panning, zooming, rotation) are implemented as convenience methods of *V3d_View* class, however *Graphic3d_Camera* class can also be used directly by application developers:
2017 // rotate camera by X axis on 30.0 degrees
2019 aTrsf.SetRotation (gp_Ax1 (gp_Pnt (0.0, 0.0, 0.0), gp_Dir (1.0, 0.0, 0.0)), 30.0);
2020 aView->Camera()->Transform (aTrsf);
2023 @subsubsection occt_visu_4_4_4 Orthographic Projection
2025 @image html view_frustum.png "Perspective and orthographic projection"
2027 The following code configures the camera for orthographic rendering:
2030 // Create an orthographic View in this Viewer
2031 Handle(V3d_View) aView = new V3d_View (VM);
2032 aView->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Orthographic);
2033 // update the Visualization in this View
2037 @subsubsection occt_visu_4_4_5 Perspective Projection
2039 **Field of view (FOVy)** - defines the field of camera view by y axis in degrees (45° is default).
2041 @image html camera_perspective.png "Perspective frustum"
2043 The following code configures the camera for perspective rendering:
2046 // Create a perspective View in this Viewer
2047 Handle(V3d_View) aView = new V3d_View(VM);
2048 aView->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Perspective);
2053 @subsubsection occt_visu_4_4_6 Stereographic Projection
2055 **IOD** - defines the intraocular distance (in world space units).
2057 There are two types of IOD:
2058 * _IODType_Absolute_ : Intraocular distance is defined as an absolute value.
2059 * _IODType_Relative_ : Intraocular distance is defined relative to the camera focal length (as its coefficient).
2061 **Field of view (FOV)** - defines the field of camera view by y axis in degrees (45° is default).
2063 **ZFocus** - defines the distance to the point of stereographic focus.
2065 @image html stereo.png "Stereographic projection"
2067 To enable stereo projection, your workstation should meet the following requirements:
2069 * The graphic card should support quad buffering.
2070 * You need active 3D glasses (LCD shutter glasses).
2071 * The graphic driver needs to be configured to impose quad buffering for newly created OpenGl contexts; the viewer and the view should be created after that.
2073 In stereographic projection mode the camera prepares two projection matrices to display different stereo-pictures for the left and for the right eye. In a non-stereo camera this effect is not visible because only the same projection is used for both eyes.
2075 To enable quad buffering support you should provide the following settings to the graphic driver *opengl_caps*:
2078 Handle(OpenGl_GraphicDriver) aDriver = new OpenGl_GraphicDriver();
2079 OpenGl_Caps& aCaps = aDriver->ChangeOptions();
2080 aCaps.contextStereo = Standard_True;
2083 The following code configures the camera for stereographic rendering:
2086 // Create a Stereographic View in this Viewer
2087 Handle(V3d_View) aView = new V3d_View(VM);
2088 aView->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Stereo);
2089 // Change stereo parameters
2090 aView->Camera()->SetIOD (IODType_Absolute, 5.0);
2091 // Finally update the Visualization in this View
2095 @subsubsection occt_visu_4_4_7 View frustum culling
2097 The algorithm of frustum culling on CPU-side is activated by default for 3D viewer. This algorithm allows skipping the presentation outside camera at the rendering stage, providing better performance. The following features support this method:
2098 * *Graphic3d_Structure::CalculateBoundBox()* is used to calculate axis-aligned bounding box of a presentation considering its transformation.
2099 * *V3d_View::SetFrustumCulling* enables or disables frustum culling for the specified view.
2100 * Classes *OpenGl_BVHClipPrimitiveSet* and *OpenGl_BVHTreeSelector* handle the detection of outer objects and usage of acceleration structure for frustum culling.
2101 * *BVH_BinnedBuilder* class splits several objects with null bounding box.
2103 @subsubsection occt_visu_4_4_8 Underlay and overlay layers management
2105 In addition to interactive 3d graphics displayed in the view you can display underlying and overlying graphics: text, color scales and drawings.
2107 All *V3d* view graphical objects in the overlay are managed by the default layer manager (*V3d_LayerMgr*). The *V3d* view has a basic layer manager capable of displaying the color scale, but you can redefine this class to provide your own overlay and underlay graphics.
2109 The method *V3d_View::SetLayerMgr(const Handle (V3d_LayerMgr)& aMgr)* allows assigning a custom layer manager to the *V3d* view.
2111 There are three virtual methods to prepare graphics in the manager for further drawing: setting up layer dimensions and drawing static graphics. These methods can be redefined:
2114 void V3d_LayerMgr::Begin ()
2115 void V3d_LayerMgr::Redraw ()
2116 void V3d_LayerMgr::End ()
2119 The layer manager controls layers (*Visual3d_Layer*) and layer items (*Visual3d_LayerItem*). Both the overlay and underlay layers can be created by the layer manager.
2121 The layer entity is presented by the *Visual3d_Layer* class. This entity provides drawing services in the layer, for example:
2123 void Visual3d_Layer::DrawText
2124 void Visual3d_Layer::DrawRectangle
2125 void Visual3d_Layer::SetColor
2126 void Visual3d_Layer::SetViewport
2129 The following example demonstrates how to draw overlay graphics by the *V3d_LayerMgr*:
2132 // redefined method of V3d_LayerMgr
2133 void MyLayerMgr::Redraw ()
2135 Quantity_Color aRed (Quantity_NOC_RED);
2136 myOverlayLayer->SetColor (aRed);
2137 myOverlayLayer->DrawRectangle (0, 0, 100, 100);
2141 The layer contains layer items that will be displayed on view redraw. Such items are *Visual3d_LayerItem* entities. To manipulate *Visual3d_LayerItem* entities assigned to the layer's internal list you can use the following methods:
2144 void Visual3d_Layer::AddLayerItem (const Handle (Visual3d_LayerItem)& Item)
2145 void Visual3d_Layer::RemoveLayerItem (const Handle (Visual3d_LayerItem)& Item)
2146 void Visual3d_Layer::RemoveAllLayerItems ()
2147 const Visual3d_NListOfLayerItem& Visual3d_Layer::GetLayerItemList ()
2149 The layer's items are rendered when the method *void Visual3d_Layer::RenderLayerItems()* is called by the graphical driver.
2151 The *Visual3d_LayerItem* has virtual methods that are used to render the item:
2153 void Visual3d_LayerItem::RedrawLayerPrs ()
2154 void Visual3d_LayerItem::ComputeLayerPrs ()
2157 The item presentation can be computed before drawing by the *ComputeLayerPrs* method to save time on redraw. It also has an additional flag that is used to tell that the presentation should be recomputed:
2159 void Visual3d_LayerItem::SetNeedToRecompute (const Standard_Boolean NeedToRecompute)
2160 Standard_Boolean Visual3d_LayerItem::IsNeedToRecompute
2163 An example of *Visual3d_LayerItem* is *V3d_ColorScaleLayerItem* that represents the color scale entity as the layer's item.
2164 The *V3d_ColorScaleLayerItem* sends render requests to the color scale entity represented by it. As this entity (*V3d_ColorScale*) is assigned to the *V3d_LayerMgr* it uses its overlay layer's services for drawing:
2169 // tell V3d_ColorScale to draw itself
2170 void V3d_ColorScaleLayerItem::RedrawLayerPrs ()
2172 Visual3d_LayerItem::RedrawLayerPrs ()
2173 if (!MyColorScale.IsNull ())
2174 MyColorScale->DrawScale ();
2177 // V3d_ColorScale has a reference to a LayerMgr
2178 void V3d_ColorScale::DrawScale ()
2180 // calls V3d_ColorScale::PaintRect, V3d_ColorScale::PaintText, etc.
2183 // PaintRect method uses overlay layer of LayerMgr to draw a rectangle
2184 void V3d_ColorScale::PaintRect
2185 (const Standard_Integer X, const Standard_Integer Y,
2186 const Standard_Integer W, const Standard_Integer H,
2187 const Quantity_Color aColor,
2188 const Standard_Boolean aFilled)
2190 const Handle (Visual3d_Layer)& theLayer = myLayerMgr->Overlay ();
2192 theLayer->SetColor (aColor);
2193 theLayer->DrawRectangle (X, Y, W, H);
2198 @subsubsection occt_visu_4_4_9 View background styles
2199 There are three types of background styles available for *V3d_view*: solid color, gradient color and image.
2201 To set solid color for the background you can use the following methods:
2203 void V3d_View::SetBackgroundColor
2204 (const Quantity_TypeOfColor Type,
2205 const Quantity_Parameter V1,
2206 const Quantity_Parameter V2,
2207 const Quantity_Parameter V3)
2210 This method allows you to specify the background color in RGB (red, green, blue) or HLS (hue, lightness, saturation) color spaces, so the appropriate values of the Type parameter are *Quantity_TOC_RGB* and *Quantity_TOC_HLS*.
2212 **Note** that the color value parameters *V1,V2,V3* should be in the range between *0.0-1.0.*
2215 void V3d_View::SetBackgroundColor(const Quantity_Color &Color)
2216 void V3d_View::SetBackgroundColor(const Quantity_NameOfColor Name)
2219 The gradient background style could be set up with the following methods:
2221 void V3d_View::SetBgGradientColors
2222 (const Quantity_Color& Color1,
2223 const Quantity_Color& Color2,
2224 const Aspect_GradientFillMethod FillStyle,
2225 const Standard_Boolean update)
2227 void V3d_View::SetBgGradientColors
2228 (const Quantity_NameOfColor Color1,
2229 const Quantity_NameOfColor Color2,
2230 const Aspect_GradientFillMethod FillStyle,
2231 const Standard_Boolean update)
2234 The *Color1* and *Color2* parameters define the boundary colors of interpolation, the *FillStyle* parameter defines the direction of interpolation. You can pass *Standard_True* as the last parameter to update the view.
2236 The fill style can be also set with the method *void V3d_View::SetBgGradientStyle(const Aspect_GradientFillMethod AMethod, const Standard_Boolean update)*.
2238 To get the current background color you can use the following methods:
2240 void V3d_View::BackgroundColor
2241 (const Quantity_TypeOfColor Type,
2242 Quantity_Parameter &V1,
2243 Quantity_Parameter &V2,
2244 Quantity_Parameter &V3)
2245 Quantity_Color V3d_View::BackgroundColor()
2246 void V3d_View::GradientBackgroundColors(Quantity_Color& Color1, Quantity_Color& Color2)
2247 Aspect_GradientBackground GradientBackground()
2250 To set the image as a background and change the background image style you can use the following methods:
2252 void V3d_View::SetBackgroundImage
2253 (const Standard_CString FileName,
2254 const Aspect_FillMethod FillStyle,
2255 const Standard_Boolean update)
2256 void V3d_View::SetBgImageStyle
2257 (const Aspect_FillMethod FillStyle,
2258 const Standard_Boolean update)
2261 The *FileName* parameter defines the image file name and the path to it, the *FillStyle* parameter defines the method of filling the background with the image. The methods are:
2262 * *Aspect_FM_NONE* - draws the image in the default position;
2263 * *Aspect_FM_CENTERED* - draws the image at the center of the view;
2264 * *Aspect_FM_TILED* tiles the view with the image;
2265 * *Aspect_FM_STRETCH* stretches the image over the view.
2268 @subsubsection occt_visu_4_4_10 Dumping a 3D scene into an image file
2270 The 3D scene displayed in the view can be dumped in high resolution into an image file. The high resolution (8192x8192 on some implementations) is achieved using the Frame Buffer Objects (FBO) provided by the graphic driver. Frame Buffer Objects enable off-screen rendering into a virtual view to produce images in the background mode (without displaying any graphics on the screen).
2272 The *V3d_View* has the following methods for dumping the 3D scene:
2274 Standard_Boolean V3d_View::Dump
2275 (const Standard_CString theFile,
2276 const Image_TypeOfImage theBufferType)
2278 Dumps the scene into an image file with the view dimensions.
2281 Standard_Boolean V3d_View::Dump
2282 (const Standard_CString theFile,
2283 const Aspect_FormatOfSheetPaper theFormat,
2284 const Image_TypeOfImage theBufferType)
2286 Makes the dimensions of the output image compatible to a certain format of printing paper passed by *theFormat* argument.
2288 These methods dump the 3D scene into an image file passed by its name and path as theFile.
2290 The raster image data handling algorithm is based on the *Image_PixMap* class. The supported extensions are ".png", ".bmp", ".png", ".png".
2292 The value passed as *theBufferType* argument defines the type of the buffer for an output image <i>(RGB, RGBA, floating-point, RGBF, RGBAF)</i>. Both methods return *Standard_True* if the scene has been successfully dumped.
2294 There is also class *Image_AlienPixMap* providing import / export from / to external image files in formats supported by **FreeImage** library.
2296 **Note** that dumping the image for a paper format with large dimensions is a memory consuming operation, it might be necessary to take care of preparing enough free memory to perform this operation.
2299 Handle_Image_PixMap V3d_View::ToPixMap
2300 (const Standard_Integer theWidth,
2301 const Standard_Integer theHeight,
2302 const Image_TypeOfImage theBufferType,
2303 const Standard_Boolean theForceCentered)
2305 Dumps the displayed 3d scene into a pixmap with a width and height passed as *theWidth* and theHeight arguments.
2307 The value passed as *theBufferType* argument defines the type of the buffer for a pixmap <i>(RGB, RGBA, floating-point, RGBF, RGBAF)</i>. The last parameter allows centering the 3D scene on dumping.
2309 All these methods assume that you have created a view and displayed a 3d scene in it. However, the window used for such a view could be virtual, so you can dump the 3d scene in the background mode without displaying it on the screen. To use such an opportunity you can perform the following steps:
2310 * Create display connection;
2311 * Initialize graphic driver;
2313 * Set up the window as virtual, *Aspect_Window::SetVirtual()* ;
2314 * Create a view and an interactive context;
2315 * Assign the virtual window to the view;
2316 * Display a 3D scene;
2317 * Use one of the functions described above to dump the 3D scene.
2319 The following example demonstrates this procedure for *WNT_Window* :
2322 // create a dummy display connection
2323 Handle(Aspect_DisplayConnection) aDisplayConnection;
2325 // create a graphic driver
2326 Handle (Graphic3d_GraphicDriver) aDriver = Graphic3d::InitGraphicDriver (aDisplayConnection);
2329 Standard_Integer aDefWidth = 800;
2330 Standard_Integer aDefHeight = 600;
2331 Handle (WNT_WClass) aWClass = new WNT_WClass ("Virtual Class",DefWindowProc,
2332 CS_VREDRAW | CS_HREDRAW, 0, 0,
2333 ::LoadCursor (NULL, IDC_ARROW));
2334 Handle (WNT_Window) aWindow = new WNT_Window ("VirtualWnd", aWClass,
2335 WS_OVERLAPPEDWINDOW, 0, 0,
2336 aDefWidth, aDefHeight);
2338 // set up the window as virtual
2339 aWindow->SetVirtual (Standard_True);
2341 // create a view and an interactive context
2342 Handle (V3d_Viewer) aViewer = new V3d_Viewer (aDriver,
2343 Standard_ExtString ("Virtual"));
2344 Handle (AIS_InteractiveContext) aContext = new AIS_InteractiveContext (aViewer);
2345 Handle (V3d_View) aView = aViewer->CreateView ();
2347 // assign the virtual window to the view
2348 aView->SetWindow (aWindow);
2350 // display a 3D scene
2351 Handle (AIS_Shape) aBox = new AIS_Shape (BRepPrimAPI_MakeBox (5, 5, 5));
2352 aContext->Display (aBox);
2355 // dump the 3D scene into an image file
2356 aView->Dump ("3dscene.png");
2359 @subsubsection occt_visu_4_4_11 Printing a 3D scene
2361 The contents of a view can be printed out. Moreover, the OpenGl graphic driver used by the v3d view supports printing in high resolution. The print method uses the OpenGl frame buffer (Frame Buffer Object) for rendering the view contents and advanced print algorithms that allow printing in, theoretically, any resolution.
2363 The method *void V3d_View::Print(const Aspect_Handle hPrnDC, const Standard_Boolean showDialog, const Standard_Boolean showBackground, const Standard_CString filename, const Aspect_PrintAlgo printAlgorithm)* prints the view contents:
2365 *hPrnDC* is the printer device handle. You can pass your own printer handle or *NULL* to select the printer by the default dialog. In that case you can use the default dialog or pass *Standard_False* as the *showDialog* argument to select the default printer automatically.
2367 You can define the filename for the printer driver if you want to print out the result into a file.
2368 If you do not want to print the background, you can pass *Standard_False* as the *showBackground* argument.
2369 The *printAlgorithm* argument allows choosing between two print algorithms that define how the 3d scene is mapped to the print area when the maximum dimensions of the frame buffer are smaller than the dimensions of the print area by choosing *Aspect_PA_STRETCH* or *Aspect_PA_TILE*
2371 The first value defines the stretch algorithm: the scene is drawn with the maximum possible frame buffer dimensions and then is stretched to the whole printing area. The second value defines *TileSplit* algorithm: covering the whole printing area by rendering multiple parts of the viewer.
2373 **Note** that at the moment the printing is implemented only for Windows.
2375 @subsubsection occt_visu_4_4_12 Vector image export
2377 The 3D content of a view can be exported to the vector image file format. The vector image export is powered by the *GL2PS* library. You can export 3D scenes into a file format supported by the GL2PS library: PostScript (PS), Encapsulated PostScript (EPS), Portable Document Format (PDF), Scalable Vector Graphics (SVG), LaTeX file format and Portable LaTeX Graphics (PGF).
2379 The method *void Visual3d_View::Export (const Standard_CString FileName, const Graphic3d_ExportFormat Format, const Graphic3d_SortType aSortType, const Standard_Real Precision, const Standard_Address ProgressBarFunc, const Standard_Address ProgressObject)* of *Visual3d_View* class allows exporting a 3D scene:
2381 The *FileName* defines the output image file name and the *Format* argument defines the output file format:
2382 * *Graphic3d_EF_PostScript (PS)*,
2383 * *Graphic3d_EF_EhnPostScript (EPS)*,
2384 * *Graphic3d_EF_TEX (TEX)*,
2385 * *Graphic3d_EF_PDF (PDF)*,
2386 * *Graphic3d_EF_SVG (SVG)*,
2387 * *Graphic3d_EF_PGF (PGF)*.
2389 The *aSortType* parameter defines *GL2PS* sorting algorithm for the primitives. The *Precision, ProgressBarFunc* and *ProgressObject* parameters are implemented for future uses and at the moment have no effect.
2391 The *Export* method supports only basic 3d graphics and has several limitations:
2392 * Rendering large scenes could be slow and can lead to large output files;
2393 * Transparency is only supported for PDF and SVG output;
2394 * Textures and some effects are not supported by the *GL2PS* library.
2396 @subsubsection occt_visu_4_4_13 Ray tracing support
2398 OCCT visualization provides rendering by real-time ray tracing technique. It is allowed to switch easily between usual rasterization and ray tracing rendering modes. The core of OCCT ray tracing is written using GLSL shaders. The ray tracing has a wide list of features:
2404 * Support of non-polygon objects, such as lines, text, highlighting, selection.
2405 * Performance optimization using 2-level bounding volume hierarchy (BVH).
2407 The ray tracing algorithm is recursive (Whitted's algorithm). It uses BVH effective optimization structure. The structure prepares optimized data for a scene geometry for further displaying it in real-time. The time-consuming re-computation of the BVH is not necessary for view operations, selections, animation and even editing of the scene by transforming location of the objects. It is only necessary when the list of displayed objects or their geometry changes.
2408 To make the BVH reusable it has been added into an individual reusable OCCT package *TKMath/BVH*.
2410 There are several ray-tracing options that user can switch on/off:
2411 * Maximum ray tracing depth
2413 * Specular reflections
2414 * Adaptive anti aliasing
2415 * Transparency shadow effects
2419 Graphic3d_RenderingParams& aParams = aView->ChangeRenderingParams();
2420 // specifies rendering mode
2421 aParams.Method = Graphic3d_RM_RAYTRACING;
2422 // maximum ray-tracing depth
2423 aParams.RaytracingDepth = 3;
2424 // enable shadows rendering
2425 aParams.IsShadowEnabled = Standard_True;
2426 // enable specular reflections.
2427 aParams.IsReflectionEnabled = Standard_True;
2428 // enable adaptive anti-aliasing
2429 aParams.IsAntialiasingEnabled = Standard_True;
2430 // enable light propagation through transparent media.
2431 aParams.IsTransparentShadowEnabled = Standard_True;
2436 @subsubsection occt_visu_4_4_14 Display priorities
2438 Structure display priorities control the order, in which structures are drawn. When you display a structure you specify its priority. The lower is the value, the lower is the display priority. When the display is regenerated, the structures with the lowest priority are drawn first. The structures with the same display priority are drawn in the same order as they have been displayed. OCCT supports eleven structure display priorities.
2440 @subsubsection occt_visu_4_4_15 Z-layer support
2442 OCCT features depth-arranging functionality called z-layer. A graphical presentation can be put into a z-layer. In general, this function can be used for implementing "bring to front" functionality in a graphical application.
2447 // set z-layer to an interactive object
2448 Handle(AIS_InteractiveContext) aContext = ...
2449 Handle(AIS_InteractiveObject) anInterObj = ...
2450 Standard_Integer anId = 3;
2451 aViewer->AddZLayer (anId);
2452 aContext->SetZLayer (anInterObj, anId);
2455 For each z-layer, it is allowed to:
2456 * Enable / disable depth test for layer.
2457 * Enable / disable depth write for layer.
2458 * Enable / disable depth buffer clearing.
2459 * Enable / disable polygon offset.
2461 The corresponding method *SetZLayerOption (...)* is available in *Graphic3d_GraphicDriver* interface. You can get the options using getter from *Visual3d_ViewManager* and *V3d_Viewer*. It returns *Graphic3d_ZLayerSettings* cached in *Visual3d_ViewManager* for a given *LayerId*.
2465 // change z-layer settings
2466 Graphic3d_ZLayerSettings aSettings = aViewer->ZLayerSettings (anId);
2467 aSettings.EnableSetting (Graphic3d_ZLayerDepthTest);
2468 aSettings.EnableSetting (Graphic3d_ZLayerDepthWrite);
2469 aSettings.EnableSetting (Graphic3d_ZLayerDepthClear);
2470 aSettings.EnableSetting (Graphic3d_ZLayerDepthOffset);
2471 aViewer->SetZLayerSettings (anId, aSettings);
2475 @subsubsection occt_visu_4_4_16 Clipping planes
2477 The ability to define custom clipping planes could be very useful for some tasks. OCCT provides such an opportunity.
2479 The *Graphic3d_ClipPlane* class provides the services for clipping planes: it holds the plane equation coefficients and provides its graphical representation. To set and get plane equation coefficients you can use the following methods:
2482 Graphic3d_ClipPlane::Graphic3d_ClipPlane(const gp_Pln& thePlane)
2483 void Graphic3d_ClipPlane::SetEquation (const gp_Pln& thePlane)
2484 Graphic3d_ClipPlane::Graphic3d_ClipPlane(const Equation& theEquation)
2485 void Graphic3d_ClipPlane::SetEquation (const Equation& theEquation)
2486 gp_Pln Graphic3d_ClipPlane::ToPlane() const
2489 The clipping planes can be activated with the following method:
2491 void Graphic3d_ClipPlane::SetOn (const Standard_Boolean theIsOn)
2494 The number of clipping planes is limited. You can check the limit value via method *Graphic3d_GraphicDriver::InquirePlaneLimit()*;
2497 // get the limit of clipping planes for the current view
2498 Standard_Integer aMaxClipPlanes = aView->Viewer()->Driver()->InquirePlaneLimit();
2501 Let us see for example how to create a new clipping plane with custom parameters and add it to a view or to an object:
2503 // create a new clipping plane
2504 const Handle(Graphic3d_ClipPlane)& aClipPlane = new Graphic3d_ClipPlane();
2505 // change equation of the clipping plane
2506 Standard_Real aCoeffA = ...
2507 Standard_Real aCoeffB = ...
2508 Standard_Real aCoeffC = ...
2509 Standard_Real aCoeffD = ...
2510 aClipPlane->SetEquation (gp_Pln (aCoeffA, aCoeffB, aCoeffC, aCoeffD));
2512 aClipPlane->SetCapping (aCappingArg == "on");
2513 // set the material with red color of clipping plane
2514 Graphic3d_MaterialAspect aMat = aClipPlane->CappingMaterial();
2515 Quantity_Color aColor (1.0, 0.0, 0.0, Quantity_TOC_RGB);
2516 aMat.SetAmbientColor (aColor);
2517 aMat.SetDiffuseColor (aColor);
2518 aClipPlane->SetCappingMaterial (aMat);
2519 // set the texture of clipping plane
2520 Handle(Graphic3d_Texture2Dmanual) aTexture = ...
2521 aTexture->EnableModulate();
2522 aTexture->EnableRepeat();
2523 aClipPlane->SetCappingTexture (aTexture);
2524 // add the clipping plane to an interactive object
2525 Handle(AIS_InteractiveObject) aIObj = ...
2526 aIObj->AddClipPlane (aClipPlane);
2527 // or to the whole view
2528 aView->AddClipPlane (aClipPlane);
2529 // activate the clipping plane
2530 aClipPlane->SetOn(Standard_True);
2536 @subsubsection occt_visu_4_4_17 Automatic back face culling
2538 Back face culling reduces the rendered number of triangles (which improves the performance) and eliminates artifacts at shape boundaries. However, this option can be used only for solid objects, where the interior is actually invisible from any point of view. Automatic back-face culling mechanism is turned on by default, which is controlled by *V3d_View::SetBackFacingModel()*.
2540 The following features are applied in *StdPrs_ToolShadedShape::IsClosed()*, which is used for definition of back face culling in *ShadingAspect*:
2541 * disable culling for free closed Shells (not inside the Solid) since reversed orientation of a free Shell is a valid case;
2542 * enable culling for Solids packed into a compound;
2543 * ignore Solids with incomplete triangulation.
2545 Back face culling is turned off at TKOpenGl level in the following cases:
2546 * clipping/capping planes are in effect;
2547 * for translucent objects;
2548 * with hatching presentation style.
2550 @subsection occt_visu_4_5 Examples: creating a 3D scene
2552 To create 3D graphic objects and display them in the screen, follow the procedure below:
2553 1. Create attributes.
2554 2. Create a 3D viewer.
2556 4. Create an interactive context.
2557 5. Create interactive objects.
2558 6. Create primitives in the interactive object.
2559 7. Display the interactive object.
2561 @subsubsection occt_visu_4_5_1 Create attributes
2566 Quantity_Color aBlack (Quantity_NOC_BLACK);
2567 Quantity_Color aBlue (Quantity_NOC_MATRABLUE);
2568 Quantity_Color aBrown (Quantity_NOC_BROWN4);
2569 Quantity_Color aFirebrick (Quantity_NOC_FIREBRICK);
2570 Quantity_Color aForest (Quantity_NOC_FORESTGREEN);
2571 Quantity_Color aGray (Quantity_NOC_GRAY70);
2572 Quantity_Color aMyColor (0.99, 0.65, 0.31, Quantity_TOC_RGB);
2573 Quantity_Color aBeet (Quantity_NOC_BEET);
2574 Quantity_Color aWhite (Quantity_NOC_WHITE);
2577 Create line attributes.
2580 Handle(Graphic3d_AspectLine3d) anAspectBrown = new Graphic3d_AspectLine3d();
2581 Handle(Graphic3d_AspectLine3d) anAspectBlue = new Graphic3d_AspectLine3d();
2582 Handle(Graphic3d_AspectLine3d) anAspectWhite = new Graphic3d_AspectLine3d();
2583 anAspectBrown->SetColor (aBrown);
2584 anAspectBlue ->SetColor (aBlue);
2585 anAspectWhite->SetColor (aWhite);
2588 Create marker attributes.
2590 Handle(Graphic3d_AspectMarker3d aFirebrickMarker = new Graphic3d_AspectMarker3d();
2591 // marker attributes
2592 aFirebrickMarker->SetColor (Firebrick);
2593 aFirebrickMarker->SetScale (1.0);
2594 aFirebrickMarker->SetType (Aspect_TOM_BALL);
2596 // it is a preferred way (supports full-color images on modern hardware).
2597 aFirebrickMarker->SetMarkerImage (theImage)
2600 Create facet attributes.
2602 Handle(Graphic3d_AspectFillArea3d) aFaceAspect = new Graphic3d_AspectFillArea3d();
2603 Graphic3d_MaterialAspect aBrassMaterial (Graphic3d_NOM_BRASS);
2604 Graphic3d_MaterialAspect aGoldMaterial (Graphic3d_NOM_GOLD);
2605 aFaceAspect->SetInteriorStyle (Aspect_IS_SOLID);
2606 aFaceAspect->SetInteriorColor (aMyColor);
2607 aFaceAspect->SetDistinguishOn ();
2608 aFaceAspect->SetFrontMaterial (aGoldMaterial);
2609 aFaceAspect->SetBackMaterial (aBrassMaterial);
2610 aFaceAspect->SetEdgeOn();
2613 Create text attributes.
2615 Handle(Graphic3d_AspectText3d) aTextAspect = new Graphic3d_AspectText3d (aForest, Graphic3d_NOF_ASCII_MONO, 1.0, 0.0);
2618 @subsubsection occt_visu_4_5_2 Create a 3D Viewer (a Windows example)
2621 // create a default connection
2622 Handle(Aspect_DisplayConnection) aDisplayConnection;
2623 // create a graphic driver from default connection
2624 Handle(OpenGl_GraphicDriver) aGraphicDriver = new OpenGl_GraphicDriver (GetDisplayConnection());
2626 TCollection_ExtendedString aName ("3DV");
2627 myViewer = new V3d_Viewer (aGraphicDriver,aName.ToExtString(), "");
2628 // set parameters for V3d_Viewer
2629 // defines default lights -
2630 // positional-light 0.3 0.0 0.0
2631 // directional-light V3d_XnegYposZpos
2632 // directional-light V3d_XnegYneg
2634 a3DViewer->SetDefaultLights();
2635 // activates all the lights defined in this viewer
2636 a3DViewer->SetLightOn();
2637 // set background color to black
2638 a3DViewer->SetDefaultBackgroundColor (Quantity_NOC_BLACK);
2642 @subsubsection occt_visu_4_5_3 Create a 3D view (a Windows example)
2644 It is assumed that a valid Windows window may already be accessed via the method *GetSafeHwnd()*.
2646 Handle (WNT_Window) aWNTWindow = new WNT_Window (GetSafeHwnd());
2647 myView = myViewer->CreateView();
2648 myView->SetWindow (aWNTWindow);
2651 @subsubsection occt_visu_4_5_4 Create an interactive context
2654 myAISContext = new AIS_InteractiveContext (myViewer);
2657 You are now able to display interactive objects such as an *AIS_Shape*.
2660 TopoDS_Shape aShape = BRepAPI_MakeBox (10, 20, 30).Solid();
2661 Handle(AIS_Shape) anAISShape = new AIS_Shape(aShape);
2662 myAISContext->Display (anAISShape);
2665 @subsubsection occt_visu_4_5_5 Create your own interactive object
2667 Follow the procedure below to compute the presentable object:
2669 1. Build a presentable object inheriting from *AIS_InteractiveObject* (refer to the Chapter on <a href="#occt_visu_2_1">Presentable Objects</a>).
2670 2. Reuse the *Prs3d_Presentation* provided as an argument of the compute methods.
2672 **Note** that there are two compute methods: one for a standard representation, and the other for a degenerated representation, i.e. in hidden line removal and wireframe modes.
2675 Let us look at the example of compute methods
2679 myPresentableObject::Compute
2680 (const Handle(PrsMgr_PresentationManager3d)& thePrsManager,
2681 const Handle(Prs3d_Presentation)& thePrs,
2682 const Standard_Integer theMode)
2688 myPresentableObject::Compute (const Handle(Prs3d_Projector)& ,
2689 const Handle(Prs3d_Presentation)& thePrs)
2695 @subsubsection occt_visu_4_5_6 Create primitives in the interactive object
2697 Get the group used in *Prs3d_Presentation*.
2700 Handle(Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (thePrs);
2703 Update the group attributes.
2706 aGroup->SetPrimitivesAspect (anAspectBlue);
2709 Create two triangles in *aGroup*.
2712 Standard_Integer aNbTria = 2;
2713 Handle(Graphic3d_ArrayOfTriangles) aTriangles = new Graphic3d_ArrayOfTriangles (3 * aNbTria, 0, Standard_True);
2714 Standard_Integer anIndex;
2715 for (anIndex = 1; anIndex <= aNbTria; nt++)
2717 aTriangles->AddVertex (anIndex * 5., 0., 0., 1., 1., 1.);
2718 aTriangles->AddVertex (anIndex * 5 + 5, 0., 0., 1., 1., 1.);
2719 aTriangles->AddVertex (anIndex * 5 + 2.5, 5., 0., 1., 1., 1.);
2721 aGroup->BeginPrimitives();
2722 aGroup->AddPrimitiveArray (aTriangles);
2723 aGroup->EndPrimitives();
2726 The methods *BeginPrimitives()* and *EndPrimitives()* are used when creating a set of various primitives in the same group.
2727 Use the polyline function to create a boundary box for the *thePrs* structure in group *aGroup*.
2730 Standard_Real Xm, Ym, Zm, XM, YM, ZM;
2731 thePrs->MinMaxValues (Xm, Ym, Zm, XM, YM, ZM);
2733 Handle(Graphic3d_ArrayOfPolylines) aPolylines = new Graphic3d_ArrayOfPolylines (16, 4);
2734 aPolylines->AddBound (4);
2735 aPolylines->AddVertex (Xm, Ym, Zm);
2736 aPolylines->AddVertex (Xm, Ym, ZM);
2737 aPolylines->AddVertex (Xm, YM, ZM);
2738 aPolylines->AddVertex (Xm, YM, Zm);
2739 aPolylines->AddBound (4);
2740 aPolylines->AddVertex (Xm, Ym, Zm);
2741 aPolylines->AddVertex (XM, Ym, Zm);
2742 aPolylines->AddVertex (XM, Ym, ZM);
2743 aPolylines->AddVertex (XM, YM, ZM);
2744 aPolylines->AddBound (4);
2745 aPolylines->AddVertex (XM, YM, Zm);
2746 aPolylines->AddVertex (XM, Ym, Zm);
2747 aPolylines->AddVertex (XM, YM, Zm);
2748 aPolylines->AddVertex (Xm, YM, Zm);
2749 aPolylines->AddBound (4);
2750 aPolylines->AddVertex (Xm, YM, ZM);
2751 aPolylines->AddVertex (XM, YM, ZM);
2752 aPolylines->AddVertex (XM, Ym, ZM);
2753 aPolylines->AddVertex (Xm, Ym, ZM);
2755 aGroup->BeginPrimitives();
2756 aGroup->AddPrimitiveArray(aPolylines);
2757 aGroup->EndPrimitives();
2760 Create text and markers in group *aGroup*.
2763 static char* texte[3] =
2765 "Application title",
2767 "My company address."
2769 Handle(Graphic3d_ArrayOfPoints) aPtsArr = new Graphic3d_ArrayOfPoints (2, 1);
2770 aPtsArr->AddVertex (-40.0, -40.0, -40.0);
2771 aPtsArr->AddVertex (40.0, 40.0, 40.0);
2772 aGroup->BeginPrimitives();
2773 aGroup->AddPrimitiveArray (aPtsArr);
2774 aGroup->EndPrimitives();
2776 Graphic3d_Vertex aMarker (0.0, 0.0, 0.0);
2777 for (i=0; i <= 2; i++)
2779 aMarker.SetCoord (-(Standard_Real )i * 4 + 30,
2780 (Standard_Real )i * 4,
2781 -(Standard_Real )i * 4);
2782 aGroup->Text (texte[i], Marker, 20.);
2787 @section occt_visu_5 Mesh Visualization Services
2789 <i>MeshVS</i> (Mesh Visualization Service) component extends 3D visualization capabilities of Open CASCADE Technology. It provides flexible means of displaying meshes along with associated pre- and post-processor data.
2791 From a developer's point of view, it is easy to integrate the *MeshVS* component into any mesh-related application with the following guidelines:
2793 * Derive a data source class from the *MeshVS_DataSource* class.
2794 * Re-implement its virtual methods, so as to give the <i>MeshVS</i> component access to the application data model. This is the most important part of the job, since visualization performance is affected by performance of data retrieval methods of your data source class.
2795 * Create an instance of <i>MeshVS_Mesh</i> class.
2796 * Create an instance of your data source class and pass it to a <i>MeshVS_Mesh</i> object through the <i>SetDataSource()</i> method.
2797 * Create one or several objects of <i>MeshVS_PrsBuilder</i>-derived classes (standard, included in the <i>MeshVS</i> package, or your custom ones).
2798 * Each <i>PrsBuilder</i> is responsible for drawing a <i> MeshVS_Mesh</i> presentation in a certain display mode(s) specified as a <i>PrsBuilder</i> constructor's argument. Display mode is treated by <i>MeshVS</i> classes as a combination of bit flags (two least significant bits are used to encode standard display modes: wireframe, shading and shrink).
2799 * Pass these objects to the <i>MeshVS_Mesh::AddBuilder()</i> method. <i>MeshVS_Mesh</i> takes advantage of improved selection highlighting mechanism: it highlights its selected entities itself, with the help of so called "highlighter" object. You can set one of <i>PrsBuilder</i> objects to act as a highlighter with the help of a corresponding argument of the <i>AddBuilder()</i> method.
2801 Visual attributes of the <i>MeshVS_Mesh</i> object (such as shading color, shrink coefficient and so on) are controlled through <i>MeshVS_Drawer</i> object. It maintains a map "Attribute ID --> attribute value" and can be easily extended with any number of custom attributes.
2803 In all other respects, <i>MeshVS_Mesh</i> is very similar to any other class derived from <i>AIS_InteractiveObject</i> and it should be used accordingly (refer to the description of <i>AIS package</i> in the documentation).