Added TODO in test case for Debug mode
[occt.git] / dox / user_guides / visualization /
ba06f8bb 1Visualization {#occt_user_guides__visualization}
bf62b306 2========================
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bf62b306 5@section occt_visu_1 Introduction
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bf62b306 7This manual provides basic documentation on setting up and using Visualization. For advanced information on Visualization and its applications, see our offerings on our web site (Training and E-Learning) at
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bf62b306 9Visualization in Open CASCADE Technology is based on the separation of:
10 * on the one hand - the data which stores the geometry and topology of the entities you want to display and select, and
11 * 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).
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bf62b306 13@subsection occt_visu_1_1 Open CASCADE Technology Visualization and the Organization of this guide
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bf62b306 15Presentations are managed through the Presentation component, and selection through the Selection component.
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bf62b306 17To make management of these functionalities in 3D more intuitive and consequently, more transparent, *Application Interactive Services* have been created. *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.
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bf62b306 19If, 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.
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bf62b306 21The packages used to display 3D objects are the following:
72b7576f 22 * AIS
23 * StdPrs
24 * Prs3d
25 * PrsMgr
26 * V3d
27 * Graphic3d
bf62b306 29If you are concerned with 2D visualization, you must familiarize yourself with the fundamental concepts of presentation as outlined in the section on this subject in chapter Fundamental Concepts. In brief, the packages used to display 3D objects are applicable for visualization of 2D objects too.
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bf62b306 31The 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.
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bf62b306 33@image html visualization_image003.png "Key concepts and packages in visualization"
34@image latex visualization_image003.png "Key concepts and packages in visualization"
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bf62b306 36To answer different needs of CASCADE users, this user’s guide offers the following three paths in reading it.
38 * 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>.
39 * 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 possibly chapters 4 and 5 <a href="#occt_visu_4">3D Presentations</a> and <a href="#occt_visu_5">3D Resources</a>. You may want to begin with the chapter presenting AIS.
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bf62b306 41@section occt_visu_2  Fundamental Concepts
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bf62b306 43@subsection occt_visu_2_1 Presentation
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bf62b306 45In 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.
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bf62b306 47@subsubsection occt_visu_2_1_1 Structure of the Presentation
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bf62b306 49Displaying an object on the screen involves three kinds of entities:
50 * a presentable object, the *AIS_InteractiveObject*
72b7576f 51 * a viewer
52 * an interactive context, the *AIS_InteractiveContext*.
54<h4>The presentable object </h4>
bf62b306 55The 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.
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bf62b306 57Standard 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.
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bf62b306 59Each object to be presented individually must be presentable or associated with a presentable object.
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bf62b306 61<h4>The viewer </h4>
62The 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.
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bf62b306 64<h4>The Interactive Context </h4>
65The 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.
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bf62b306 67@subsubsection occt_visu_2_1_2 Presentation packages
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bf62b306 69Presentation 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.
70* *AIS* package provides all classes to implement interactive objects (presentable and selectable entities).
71* *PrsMgr* package provides all the classes needed to implement the presentation process: the *Presentation* and *PresentableObject* abstract classes and *PresentationManager3d* concrete class.
72* *StdPrs* package provides ready-to-use standard presentation algorithms of points, curves and shapes of the geometry and topology toolkits.
73* *V3d* package provides the services supported by the 3D viewer.
74* *Prs3d* package provides some 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, and so on.
75* *Graphic3d* package provides resources to create 3D graphic structures.
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bf62b306 77@subsubsection occt_visu_2_1_3 A Basic Example: How to display a 3D object
72b7576f 78
bf62b306 79~~~~~
80Void Standard_Real dx  = ...; //Parameters
81Void Standard_Real dy  = ...; //to build a wedge
82Void Standard_Real dz  = ...;
83Void Standard_Real ltx = ...;
85Handle(V3d_Viewer)aViewer = ...;
87aContext = new AIS_InteractiveContext(aViewer);
89BRepPrimAPI_MakeWedge w(dx, dy, dz, ltx);
90TopoDS_Solid & = w.Solid();
91Handle(AIS_Shape) anAis = new AIS_Shape(S);
92//creation of the presentable object
93aContext - Display(anAis);
94//Display the presentable object in the 3d viewer.
dba69de2 96
bf62b306 97The 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.
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bf62b306 99@image html visualization_image004.png "Processes involved in displaying a presentable shape"
100@image latex visualization_image004.png "Processes involved in displaying a presentable shape"
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bf62b306 102@subsection occt_visu_2_2 Selection
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bf62b306 104Objects 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.
106@image html visualization_image006.png "A model"
107@image latex visualization_image006.png "A model"
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bf62b306 109The 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.
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bf62b306 111@image html visualization_image007.png "Modeling faces with sensitive primitives"
112@image latex visualization_image007.png "Modeling faces with sensitive primitives"
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bf62b306 114@image html visualization_image008.png "In a dynamic selection, each sensitive polygon is represented by its bounding rectangle"  
115@image latex visualization_image008.png "In a dynamic selection, each sensitive polygon is represented by its bounding rectangle"
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bf62b306 117@image html visualization_image009.png "Reference to the sensitive primitive, then to the owner"
118@image latex visualization_image009.png "Reference to the sensitive primitive, then to the owner"
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bf62b306 121@subsubsection occt_visu_2_2_1 The Sensitive Primitive
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bf62b306 123The 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.
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bf62b306 125The 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.
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bf62b306 127@image html visualization_image010.png "Example of sensitive primitives"
128@image latex visualization_image010.png "Example of sensitive primitives"
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bf62b306 130In 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.
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bf62b306 132When 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.
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bf62b306 134The 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.
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bf62b306 136The 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.
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bf62b306 139@subsubsection occt_visu_2_2_2 Dynamic Selection
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bf62b306 141Dynamic selection causes objects in a view to be automatically highlighted
142as the mouse cursor moves over them. This allows the user to be certain that the picked object
143 is the correct one. Dynamic Selection is based on the following two concepts:
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bf62b306 145 * a Selectable Object (*AIS_InteractiveObject*)
146 * an Interactive Context
148<h4>Selectable Object</h4>
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bf62b306 150A 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.
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bf62b306 152Note 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.
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bf62b306 154For 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.)
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bf62b306 156The 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.
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158<h4>Interactive Context</h4>
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bf62b306 160The interactive context is used to manage both selectable objects and selection processes.
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bf62b306 162Selection 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.
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bf62b306 164See also <a href="#occt_visu_3">AIS: Application Interactive Services</a>.
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bf62b306 166Let us consider, for example, a 3D selectable shape object, which corresponds to a topological shape.
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bf62b306 168For this class, seven selection modes can be defined:
169* mode 0 - selection of the shape itself
170* mode 1 - selection of vertices
171* mode 2 - selection of edges
172* mode 3 - selection of wires
173* mode 4 - selection of faces
174* mode 5 - selection of shells
175* mode 6 - selection of solids
176* mode 7 - selection of compsolids
177* mode 8 - selection of compounds
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bf62b306 179Selection 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.
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bf62b306 181The 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.
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183To deactivate selection mode 3 remove all those 2D areas.
bf62b306 186@subsubsection occt_visu_2_2_3 Selection Packages
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bf62b306 188The following selection packages exist : *SelectBasics*, *SelectMgr*, *Select3D*, *StdSelect*.
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bf62b306 190*SelectBasics* package contains the basic classes of the selection:
191 * the main definition of a sensitive primitive: *SensitiveEntity*
192 * the definition of a sensitive primitive owner: *EntityOwner*
193 * the algorithm used for sorting sensitive boxes: *SortAlgo*
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bf62b306 195*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*.
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bf62b306 197*SelectMgr* package is used to manage the whole dynamic selection process. It contains the *SelectableObject*, Entity Owner containing a link to its SelectableObject,* *Selection*, *SelectionManager*, and *ViewSelector* classes.
198There are also implementations of *ViewerSelector* interface for 3D selection in *StdSelect* package: *ViewerSelector3d*.
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bf62b306 200*Select3D* package contains 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.
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bf62b306 202*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 means for selection of topological objects (shapes).
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bf62b306 204@subsubsection occt_visu_2_2_4 How to use dynamic selection
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bf62b306 206Several operations must be performed prior to using dynamic selection:
2071. 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.
2082. 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.
2093. Install the process, which provides the user with the identity of the owner of the detected entities in the selection loop.
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bf62b306 211When all these steps have been carried out, follow the procedure below:
2121. Create an interactive context.
2132. Create the selectable objects and calculate their various possible selections.
2143. 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.
2154. 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.
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bf62b306 217At this stage, the selection of selectable entities in the selectors is available.
218The selection loop informs constantly the selectors with the position of the mouse and questions them about the detected entities.
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bf62b306 220Let 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.
221You define a selectable object called *House* and propose four possible selection modes for this object:
2221. selection of the house itself;
2232. selection of the rooms
2243. selection of the walls
2254. selection of the doors.
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bf62b306 227You have to write the method, which calculates the four selections above, i.e. the sensitive primitives which are activated when the mode is.
228You 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*.
229For example, let us consider a house with the following representation:
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bf62b306 231@image html visualization_image011.png "Selection of rooms in a house"
232@image latex visualization_image011.png "Selection of rooms in a house"
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bf62b306 234To build the selection, which corresponds to the mode "selection of the rooms"
235(selection 2 in the list of selection modes), use the following procedure:
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bf62b306 237~~~~~
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239Void House::ComputeSelection
bf62b306 240 (Const Handle(SelectMgr_Selection)& Sel,
241  const Standard_Integer mode {
242  switch(mode){  case 0: //Selection of the rooms
243 {  for(Standard_Integer i = 1; i = myNbRooms; i++)  { //for every room, create an instance of the owner, the given room and its name.
244 Handle(RoomOwner) aRoomOwner = new RoomOwner (Room(i), NameRoom(i)); //Room() returns a room and NameRoom() returns its name.
245 Handle(Select3d_SensitiveBox) aSensitiveBox;
246 aSensitiveBox = new Select3d_SensitiveBox
247 (aRoomOwner, Xmin, Ymin, Zmin, Xmax, Ymax, Zmax);
248  Sel - Add(aSensitiveBox);  }  break;  Case 1: ... //Selection of the doors  } //Switch
249) // ComputeSelection
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bf62b306 252@image html visualization_image012.png "Activated sensitive boxes corresponding to selection mode 0 (selection of rooms)"
253@image latex visualization_image012.png "Activated sensitive boxes corresponding to selection mode 0 (selection of rooms)"
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bf62b306 255@image html visualization_image013.png "Activated sensitive rectangles in the selector during dynamic selection in view 1"
256@image latex visualization_image013.png "Activated sensitive rectangles in the selector during dynamic selection in view 1"
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bf62b306 258@image html visualization_image014.png "Activated sensitive polygons corresponding to selection mode 1 (selection of doors)"
259@image latex visualization_image014.png "Activated sensitive polygons corresponding to selection mode 1 (selection of doors)"
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bf62b306 261@image html visualization_image015.png "Sensitive rectangles in the selector during dynamic selection in view 2"
262@image latex visualization_image015.png "Sensitive rectangles in the selector during dynamic selection in view 2"
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bf62b306 264@section occt_visu_3 Application Interactive Services
265@subsection occt_visu_3_1 Introduction
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bf62b306 267Application Interactive Services allow managing presentations and dynamic selection in a viewer in a simple and transparent manner.
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bf62b306 269The 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.
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bf62b306 271The neutral point, which is the default mode, allows easily visualizing and selecting interactive objects loaded into the context.
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bf62b306 273**Local Contexts** can be opened to prepare and use a temporary selection environment without disturbing
274the 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.
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bf62b306 276When the operation is finished, you close the current local context and return to the state
277in which you were before opening it (neutral point or previous local context).
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bf62b306 279**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.
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bf62b306 281@image html visualization_image016.png
282@image latex visualization_image016.png
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bf62b306 284An 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.
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bf62b306 286When 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.
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bf62b306 288@image html visualization_image017.png
289@image latex visualization_image017.png
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bf62b306 291It 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.
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bf62b306 293@subsection occt_visu_3_2 Interactive objects
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bf62b306 295@subsubsection occt_visu_3_2_1 Presentations
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bf62b306 297An interactive object can have as many presentations as its creator wants to give it.
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bf62b306 2993D presentations are managed by PresentationManager3D. As this is transparent in AIS, the user does not have to worry about it.
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bf62b306 301A presentation is identified by an index and by the reference to the Presentation Manager which it depends on.
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bf62b306 303By convention, the default mode of representation for the Interactive Object has index 0.
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bf62b306 305@image html visualization_image018.png
306@image latex visualization_image018.png
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bf62b306 308Calculation 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.
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bf62b306 310If you are creating your own type of interactive object, you must implement the Compute function in one of the following ways:
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bf62b306 312#### For 3D:
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bf62b306 314~~~~~
315void PackageName_ClassName::Compute
316 (const Handle(PrsMgr_PresentationManager3d)& aPresentationManager,
317  const Handle(Prs3d_Presentation)& aPresentation,
318  const Standard_Integer aMode = 0);
72b7576f 320
bf62b306 321#### For hidden line removal (HLR) mode in 3D:
323void PackageName_ClassName::Compute
324 (const Handle(Prs3d_Projector)& aProjector,
325  const Handle(Prs3d_Presentation)& aPresentation);
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bf62b306 328@subsubsection occt_visu_3_2_2 Hidden Line Removal
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bf62b306 330The 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.
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bf62b306 332By convention, the Interactive Object accepts or rejects the representation of HLR mode. It is possible to make this declaration in one of two ways:
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bf62b306 334* Initially by using one of the values of the enumeration *PrsMgr_TypeOfPresentation*:
335 * *PrsMgr_TOP_AllView*,
336 * *PrsMgr_TOP_ProjectorDependant*
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bf62b306 338* Later by using the function *PrsMgr_PresentableObject::SetTypeOfPresentation*
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bf62b306 340*AIS_Shape* class is an example of an interactive object that supports HLR representation. It supports two types of the HLR algorithm:
341* the polygonal algorithm based on the shape’s triangulation;
342* the exact algorithm that works with the shape’s real geometry.
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bf62b306 344The 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:
345 * *Prs3d_TOH_PolyAlgo* for a polygonal algorithm;
346 * *Prs3d_TOH_Algo* for an exact algorithm;
347 * *Prs3d_TOH_NotSet* if the type of algorithm is not set for the given interactive object instance.
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bf62b306 349The type of the HLR algorithm used for *AIS_Shape* can be changed by calling the *AIS_Shape::SetTypeOfHLR()* method.
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bf62b306 351The current HLR algorithm type can be obtained using *AIS_Shape::TypeOfHLR()* method is to be used.
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bf62b306 353These 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*.
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bf62b306 355So 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.
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bf62b306 357@subsubsection occt_visu_3_2_3 Presentation modes
72b7576f 358
bf62b306 359There are four types of interactive objects in AIS:
360 * the "construction element" or Datum,
361 * the Relation (dimensions and constraints)
362 * the Object
363 * the None type (when the object is of an unknown type).
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bf62b306 365Inside 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:
366 * *AIS_InteractiveObject::Type*
367 * *AIS_InteractiveObject::Signature*.
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bf62b306 369**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>).
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bf62b306 371The 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.
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bf62b306 373Consequently, to get information about this class it is necessary to use virtual function *AIS_InteractiveObject::AcceptDisplayMode*.
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bf62b306 375#### Display Mode
72b7576f 376
bf62b306 377The 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.
72b7576f 378
bf62b306 379#### Highlight Mode
72b7576f 380
bf62b306 381At dynamic detection, the presentation echoed by the Interactive Context, is by default the presentation already on the screen.
72b7576f 382
bf62b306 383The 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.
72b7576f 384
bf62b306 385Note 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).
72b7576f 386
bf62b306 387For 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.
72b7576f 388
bf62b306 389#### Infinite Status
390If you don’t 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.
72b7576f 391
bf62b306 392Let us take for example the class called *IShape* representing an interactive object :
72b7576f 393
bf62b306 394~~~~~
396 (const TopoDS_Shape& SH, PrsMgr_TypeOfPresentation aType):
397 AIS_InteractiveObject(aType), myShape(SH), myDrwr(new AIS_Drawer()) {SetHilightMode(0);} 
398void myPk_IShape::Compute
399 (const Handle(PrsMgr_PresentationManager3d) & PM,
400 const Handle(Prs3d_Presentation)& P,  
401 const Standard_Integer TheMode)
403 switch (TheMode){
404 case 0:
405 StdPrs_WFDeflectionShape::Add (P,myShape,myDrwr); //algo for calculation of wireframe presentation break;
406 case 1:
407 StdPrs_ShadedShape::Add (P,myShape,myDrwr); //algo for calculation of shading presentation.
408 break;
409 }
411void myPk_IsShape::Compute
412 (const Handle(Prs3d_Projector)& Prj,
413 const Handle(Prs3d_Presentation) P)
415 StdPrs_HLRPolyShape::Add(P,myShape,myDrwr);
416 //Hidden line mode calculation algorithm
72b7576f 419
bf62b306 420@subsubsection occt_visu_3_2_4 Selection
72b7576f 421
bf62b306 422An 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).
72b7576f 423
bf62b306 424The set of sensitive primitives, which correspond to a given mode, is stocked in a SELECTION (*SelectMgr_Selection*).
72b7576f 425
bf62b306 426Each 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*.
72b7576f 427
bf62b306 428The 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*.
72b7576f 429
bf62b306 430A 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.
72b7576f 431
bf62b306 432Moreover, 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*.
72b7576f 433
bf62b306 434You can change the default selection mode index of an Interactive Object using the following functions:
435 * *AIS_InteractiveObject::HasSelectionMode* checks if there is a selection mode;
436 * *AIS_InteractiveObject::SelectionMode* check the current selection mode;
437 * *AIS_InteractiveContext::SetSelectionMode* sets a selection mode;
438 * *AIS_InteractiveContext::UnsetSelectionMode* unsets a selection mode.
440These 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:
441 * *AIS_InteractiveObject::HasSelectionPriority* checks if there is a selection priority setting for the owner;
442 * *AIS_InteractiveObject::SelectionPriority* checks the current priority;
443 * *AIS_InteractiveObject::SetSelectionPriority* sets a priority;
444 * *AIS_InteractiveObject::UnsetSelectionPriority* unsets the priority.
447@subsubsection occt_visu_3_2_5 Graphic attributes
72b7576f 448
bf62b306 449Keep in mind the following points concerning graphic attributes:
450 * Each interactive object can have its own visualization attributes.
451 * 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
452 * 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.)
453 * 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.
72b7576f 454
72b7576f 455
bf62b306 456@image html visualization_image019.png "Figure 13. Redefinition of virtual functions for changes in AIS_Point"
457@image latex visualization_image019.png "Figure 13. Redefinition of virtual functions for changes in AIS_Point"
72b7576f 458
bf62b306 459@image html visualization_image020.png "Figure 14. Redefinition of virtual functions for changes in AIS_Shape."
460@image latex visualization_image020.png "Figure 14. Redefinition of virtual functions for changes in AIS_Shape."
72b7576f 461
bf62b306 462The following virtual functions provide settings for color, width, material and transparency:
463 * *AIS_InteractiveObject::UnsetColor*
464 * *AIS_InteractiveObject::SetWidth*
465 * *AIS_InteractiveObject::UnsetWidth*
466 * *AIS_InteractiveObject::SetMaterial (const Graphic3d_NameOfPhysicalMaterial & aName)*
467 * *AIS_InteractiveObject::SetMaterial  (const Graphic3d_MaterialAspect & aMat)*
468 * *AIS_InteractiveObject::UnsetMaterial*
469 * *AIS_InteractiveObject::SetTransparency*
470 * *AIS_InteractiveObject::UnsetTransparency*
72b7576f 471
bf62b306 472For other types of attribute, it is appropriate to change the Drawer of the object directly using:
473 * *AIS_InteractiveObject::SetAttributes*
474 * *AIS_InteractiveObject::UnsetAttributes*
72b7576f 475
bf62b306 476It is important to know which functions may imply the recalculation of presentations of the object.
72b7576f 477
bf62b306 478If the presentation mode of an interactive object is to be updated, a flag from *PrsMgr_PresentableObject* indicates this.
72b7576f 479
bf62b306 480The mode can be updated using the functions *Display* and *Redisplay* in *AIS_InteractiveContext*.
72b7576f 481
bf62b306 482@subsubsection occt_visu_3_2_6 Complementary Services
72b7576f 483
bf62b306 484When you use complementary services for interactive objects, pay special attention to the cases mentioned below.
72b7576f 485
bf62b306 486#### Change the location of an interactive object
72b7576f 487
bf62b306 488The following functions allow temporarily "moving" the representation and selection of Interactive Objects in a view without recalculation.
489 * *AIS_InteractiveContext::SetLocation*
490 * *AIS_InteractiveContext::ResetLocation*
491 * *AIS_InteractiveContext::HasLocation*
492 * *AIS_InteractiveContext::Location*
494#### Connect an interactive object to an applicative entity
72b7576f 495
bf62b306 496Each Interactive Object has functions that allow attributing it an *Owner* in form of a *Transient*.
497 * *AIS_InteractiveObject::SetOwner*
498 * *AIS_InteractiveObject::HasOwner*
499 * *AIS_InteractiveObject::Owner*
72b7576f 500
bf62b306 501An interactive object can therefore be associated or not with an applicative entity, without affecting its behavior.
72b7576f 502
bf62b306 503#### Resolving coincident topology
72b7576f 504
bf62b306 505Due 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.
72b7576f 506
bf62b306 507To 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.
72b7576f 508
bf62b306 509The method *AIS_InteractiveObject::SetPolygonOffsets (const Standard_Integer aMode, const Standard_Real aFactor, const Standard_Real aUnits)* allows setting up the polygon offsets.
72b7576f 510
bf62b306 511The parameter *aMode* can contain various combinations of *Aspect_PolygonOffsetMode* enumeration elements:
512 * *Aspect_POM_None*
513 * *Aspect_POM_Off*
72b7576f 514 * Aspect_POM_Fill
515 * Aspect_POM_Line
516 * Aspect_POM_Point
517 * Aspect_POM_All
bf62b306 519The 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:
521 offset = aFactor * m + aUnits * r
523where *m* is the maximum depth slope for the currently displayed polygons, r is the minimum depth resolution (implementation-specific).
72b7576f 524
bf62b306 525Negative offset values move polygons closer to the viewer while positive values shift polygons away.
72b7576f 526
bf62b306 527**Warning**
529This 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.
72b7576f 530
bf62b306 531You can use the following functions to obtain the current settings for polygon offsets:
533 void AIS_InteractiveObject::PolygonOffsets
534 (Standard_Integer &aMode,
535  Standard_Real &aFactor,
536  Standard_Real &aUnits)
537 Standard_Boolean AIS_InteractiveObject::HasPolygonOffsets()
72b7576f 539
bf62b306 540The same operation could be performed for the interactive object known by the *AIS_InteractiveContext* with the following methods:
542void AIS_InteractiveContext::SetPolygonOffsets
543 (const Handle(AIS_InteractiveObject) &anObj,
544  const Standard_Integer aMode,
545  const Standard_Real aFactor,
546  const Standard_Real aUnits)
547void AIS_InteractiveContext::PolygonOffsets
548 (const Handle(AIS_InteractiveObject) &anObj,
549  Standard_Integer &aMode,
550  Standard_Real &aFactor,
551  Standard_Real &aUnits)
552Standard_Boolean     AIS_InteractiveContext::HasPolygonOffsets
553 (const Handle(AIS_InteractiveObject) &anObj)
72b7576f 555
bf62b306 556@subsection occt_visu_3_3 Interactive Context
72b7576f 557
bf62b306 558@subsubsection occt_visu_3_3_1 Rules
72b7576f 559
bf62b306 560The Interactive Context allows us to manage in a transparent way, the graphic and "selectable" behavior of interactive objects in one or more viewers. Most functions which allow us to modify the attributes of interactive objects, and which were presented in the preceding chapter, will be looked at again here.
72b7576f 561
bf62b306 562There 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.
72b7576f 563
bf62b306 564~~~~~
565Handle (AIS_Shape) TheAISShape = new AIS_Shape (ashape);
566 myIntContext-Display(TheAISShape);
567 myIntContext-SetDisplayMode(TheAISShape ,1);
568 myIntContext-SetColor(TheAISShape,Quantity_NOC_RED);
72b7576f 570
bf62b306 571You can also write
72b7576f 572
bf62b306 573~~~~~
574Handle (AIS_Shape) TheAISShape = new AIS_Shape (ashape);
575 TheAISShape-SetColor(Quantity_NOC_RED);
576 TheAISShape-SetDisplayMode(1);
577 myIntContext-Display(TheAISShape);
72b7576f 579
bf62b306 580@subsubsection occt_visu_3_3_2 Groups of functions
72b7576f 581
bf62b306 582You must distinguish two states in the Interactive Context:
583* No Open Local Context; which will be referred to as Neutral Point.
584* One or several open local contexts, each representing a temporary state of selection and presentation.
72b7576f 585
bf62b306 586Some 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.
72b7576f 587
bf62b306 588The Interactive Context is composed of many functions, which can be conveniently grouped according to the theme:
589 * management proper to the context;
590 * management in the local context;
591 * presentations and selection in open/closed context;
592 * selection strictly speaking.
72b7576f 593
72b7576f 594
bf62b306 595@subsubsection occt_visu_3_3_3 Management of the Interactive Context
72b7576f 596
bf62b306 597The Interactive Context is made up of a Principal Viewer and, optionally, a trash bin or "Collector" Viewer. It also has a group of adjustable settings allowing you to personalize the behavior of presentations and selections:
598 * Default Drawer, containing all the color and line attributes which can be used by interactive objects, which do not have their own attributes.
599 * Default Visualization Mode for interactive objects. By default: *mode 0* ;
600 * Highlight color of entities detected by mouse movement. By default: *Quantity_NOC_CYAN1*;
601 * Pre-selection color. By default: *Quantity_NOC_GREEN*;
602 * Selection color (when you click on a detected object). By default: *Quantity_NOC_GRAY80*;
603 * Sub-Intensity color. By default: *Quantity_NOC_GRAY40*.
72b7576f 604
bf62b306 605All of these settings can be modified by functions proper to the Context.
72b7576f 606
bf62b306 607When 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.
72b7576f 608
bf62b306 609Let us examine the case of two interactive objects: *obj1* and *obj2*:
72b7576f 610
bf62b306 611~~~~~
612TheCtx-Display(obj1,Standard_False); // False = no viewer update
613TheCtx-Display(obj2,Standard_True); // True = viewer update
616// obj2 is visualised in mode 2 (if it accepts this mode)
617// obj1 stays visualised in its mode 3.
72b7576f 619
bf62b306 620*PresentationManager3D* and a *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.
72b7576f 621
bf62b306 622@subsection occt_visu_3_4 Local Context
623@subsubsection occt_visu_3_4_1 Rules and Conventions
72b7576f 624
bf62b306 625 * Opening a local context allows preparing an environment for temporary presentations and selections, which will disappear once the local context is closed.
626 * It is possible to open several local contexts, but only the last one will be active.
627 * 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.
628 * Each local context has an index created when the context opens. You should close the local context, which you have opened.
72b7576f 629
bf62b306 630The 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*.
631 * 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.
632 * The state of a temporary interactive object in a local context can only be modified while another local context is open.
72b7576f 633
bf62b306 634**Warning**
72b7576f 635
bf62b306 636The 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.
72b7576f 637
bf62b306 638@subsubsection occt_visu_3_4_2 Management of Local Context
72b7576f 639
bf62b306 640The local context can be opened using method *AIS_InteractiveContext::OpenLocalContext*. The following options are available:
641 * *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.
642 * *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*.
643 * *AcceptEraseOfObjects*: authorises other local contexts to erase the interactive objects present in this context. This option is rarely used. The last option has no current use.
72b7576f 644
bf62b306 645This function returns the index of the created local context. It should be kept and used when the context is closed.
72b7576f 646
bf62b306 647To load objects visualized at Neutral Point into a local context or remove them from it use methods
649 AIS_InteractiveContext::UseDisplayedObjects
650 AIS_InteractiveContext::NotUseDisplayedObjects
652Closing Local Contexts is done by:
654 AIS_InteractiveContext::CloseLocalContext
655 AIS_InteractiveContext::CloseAllContexts
72b7576f 657
bf62b306 658*Warning*
659When the index isn’t 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.
72b7576f 660
bf62b306 661To 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.
72b7576f 662
bf62b306 663When you close a local context, all temporary interactive objects are deleted, all selection modes concerning the context are cancelled, and all content filters are emptied.
72b7576f 664
72b7576f 665
bf62b306 666@subsubsection occt_visu_3_4_3 Presentation in a Neutral Point
72b7576f 667
bf62b306 668You 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.
72b7576f 669
bf62b306 670Neutral Point should be used to visualize the interactive objects, which represent and select an applicative entity. Visualization and Erasing orders are straightforward:
72b7576f 671
bf62b306 672~~~~~
674 (const Handle(AIS_InteractiveObject)& anIobj,
675  const Standard_Boolean updateviewer=Standard_True);
678 (const Handle(AIS_InteractiveObject)& anIobj,
679  const Standard_Integer amode,
680  const Standard_Integer aSelectionMode,
681  const Standard_Boolean updateviewer = Standard_True,
682  const Standard_Boolean allowdecomposition = Standard_True);
684 AIS_InteractiveContext::Erase
685 AIS_InteractiveContext::EraseMode
686 AIS_InteractiveContext::ClearPrs
687 AIS_InteractiveContext::Redisplay
688 AIS_InteractiveContext::Remove
689 AIS_InteractiveContext::EraseAll
690 AIS_InteractiveContext::Hilight
691 AIS_InteractiveContext::HilightWithColor
694Bear in mind the following points:
695 * It is recommended to display and erase interactive objects when no local context is opened, and open a local context for local selection only.
696 * 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).
697 * 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.
698 * 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.
699 * 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.
700 * 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.
701 * *Erase()* with *putInCollector = Standard_True* might be slow as it computes again the object presentation in the Collector. Set *putInCollector* to *Standard_False* if you simply want to hide the object’s presentation temporarily.
702 * 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.
703 * 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.
72b7576f 704
bf62b306 705@subsubsection occt_visu_3_4_4 Presentation in Local Context
72b7576f 706
bf62b306 707In open local context, the *Display* functions presented above can be as well.
72b7576f 708
bf62b306 709**WARNING**
72b7576f 710
bf62b306 711The 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*.
72b7576f 712
bf62b306 713You can activate or deactivate specific selection modes in the local open context in several different ways:
714Use the Display functions with the appropriate modes.
717 AIS_InteractiveContext::ActivateStandardMode
718 //can be used only if a Local Context is opened.
719 AIS_InteractiveContext::DeactivateStandardMode
720 AIS_InteractiveContext::ActivatedStandardModes
721 AIS_InteractiveContext::SetShapeDecomposition
72b7576f 723
bf62b306 724This 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.
72b7576f 725
bf62b306 726**WARNING**
72b7576f 727
bf62b306 728If you have opened a local context by loading an object with the default options *(AllowShapeDecomposition = Standard_True)*, 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)*.
72b7576f 729
bf62b306 730Load an interactive object by the function *AIS_InteractiveContext::Load*.
72b7576f 731
bf62b306 732This 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.
72b7576f 733
bf62b306 734Use *AIS_InteractiveContext::Activate* and *AIS_InteractiveContext::Deactivate* to directly activate/deactivate selection modes on an object.
72b7576f 735
bf62b306 736@subsubsection occt_visu_3_4_5 Filters
72b7576f 737
bf62b306 738When Interactive objects have been "prepared" in the local context, you can add rejection filters. The root class of objects is *SelectMgr_Filter*. The principle behind it is straightforward: a filter tests to see whether the owners *(SelectMgr_EntityOwner)* detected in mouse position by the Local context selector answer *OK*. If so, it is kept, otherwise it is rejected.
72b7576f 739
bf62b306 740You can create a custom class of filter objects by implementing the deferred function *IsOk()*:
72b7576f 741
bf62b306 742~~~~~
743class MyFilter : public SelectMgr_Filter { };
744virtual Standard_Boolean MyFilter::IsOk
745 (const Handle(SelectMgr_EntityOwner)& anObj) const = 0;
72b7576f 747
bf62b306 748In *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*).
72b7576f 749
bf62b306 750There are Standard filters, which have already been implemented in several packages:
751 * *StdSelect_EdgeFilter* - for edges, such as lines and circles;
752 * *StdSelect_FaceFilter* - for faces, such as planes, cylinders and spheres;
753 * *StdSelect_ShapeTypeFilter* - for shape types, such as compounds, solids, shells and wires;
754 * *AIS_TypeFilter* - for types of interactive objects;
755 * *AIS_SignatureFilter* - for types and signatures of interactive objects;
756 * *AIS_AttributeFilter* - for attributes of Interactive Objects, such as color and width.
72b7576f 757
bf62b306 758As 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*.
72b7576f 759
bf62b306 760**WARNING**
762Only 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.
72b7576f 763
bf62b306 764There are several functions to manipulate filters:
765 * *AIS_InteractiveContext::AddFilter* adds a filter passed as an argument.
766  * *AIS_InteractiveContext::RemoveFilter* removes a filter passed as an argument.
767 * *AIS_InteractiveContext::RemoveFilters* removes all present filters.
768 * *AIS_InteractiveContext::Filters* gets the list of filters active in a local context.
dba69de2 769
72b7576f 770<h4>Example </h4>
bf62b306 772~~~~~
774// no object in neutral point is loaded
72b7576f 775
bf62b306 776myContext-ActivateStandardMode(TopAbs_Face);
777//activates decomposition of shapes into faces.
778Handle (AIS_Shape) myAIShape = new AIS_Shape ( ATopoShape);
72b7576f 779
bf62b306 780myContext-Display(myAIShape,1,-1,Standard_True,Standard_True);
72b7576f 781
bf62b306 782//shading visualization mode, no specific mode, authorization for //decomposition into sub-shapes. At this Stage, myAIShape is decomposed into faces...
72b7576f 783
bf62b306 784Handle(StdSelect_FaceFilter) Fil1= new
785 StdSelect_FaceFilter(StdSelect_Revol);
786Handle(StdSelect_FaceFilter) Fil2= new
787      StdSelect_FaceFilter(StdSelect_Plane);
72b7576f 788
bf62b306 789myContext-AddFilter(Fil1);
72b7576f 791
bf62b306 792//only faces of revolution or planar faces will be selected
794myContext-MoveTo( xpix,ypix,Vue);
795// detects the mouse position
72b7576f 797
bf62b306 798@subsubsection occt_visu_3_4_6 Selection in the Local Context
800Dynamic 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:
801 * *AIS_InteractiveContext::MoveTo* - passes mouse position to Interactive Context selectors
802 * *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
803 * *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.
804 * *AIS_InteractiveContext::Select* selects everything found in the surrounding area.
805 * *AIS_InteractiveContext::ShiftSelect* selects what was not previously in the list of selected, deselects those already present.
807Highlighting 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 :
809 AIS_InteractiveContext::SetAutomaticHilight
810 AIS_InteractiveContext::AutomaticHilight
72b7576f 812
bf62b306 813If 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.
817When 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.
819You can question the Interactive context by moving the mouse. The following functions can be used:
820 * *AIS_InteractiveContext::HasDetected* informs if something has been detected;
821 * *AIS_InteractiveContext::HasDetectedShape* informs if it is a shape;
822 * *AIS_InteractiveContext::DetectedShape* gets the shape if the detected entity is an object;
823 * *AIS_InteractiveContext::DetectedInteractive* gets the interactive object if the detected entity is an object.
825After 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:
826 * *AIS_InteractiveContext::InitCurrent* initiates a scan of this list;
827 * *AIS_InteractiveContext::MoreCurrent* extends the scan;
828 * *AIS_InteractiveContext::NextCurrent* resumes the scan;
829 * *AIS_InteractiveContext::Current* gets the name of the current object detected in the scan;
830 * *AIS_InteractiveContext::FirstCurrentObject* gets the first current interactive object;
831 * *AIS_InteractiveContext::HilightCurrents* highlights current objects;
832 * *AIS_InteractiveContext::UnhilightCurrents* removes highlight from current objects;
833 * *AIS_InteractiveContext::ClearCurrents* empties the list of current objects in order to update it;
834 * *AIS_InteractiveContext::IsCurrent* finds the current object.
836In the Local Context, you can explore the list of selected objects available. The following functions can be used:
837 * *AIS_InteractiveContext::InitSelected* initiates the list of objects;
838 * *AIS_InteractiveContext::MoreSelected* extends the list of objects;
839 * *AIS_InteractiveContext::NextSelected* resumes a scan;
840 * *AIS_InteractiveContext::SelectedShape* gets the name of the selected object;
841 * *AIS_InteractiveContext::HasSelectedShape* checks if the selected shape is obtained;
842 * *AIS_InteractiveContext::Interactive* gets the picked interactive object;
843 * *AIS_InteractiveContext::HasApplicative* checks if the applicative object has an owner from Interactive attributed to it;
844 * *AIS_InteractiveContext::Applicative* gets the owner of the detected applicative entity;
845 * *AIS_InteractiveContext::IsSelected* gets the name of the selected object.
72b7576f 846
72b7576f 847
bf62b306 848<h4>Example </h4>
851while (myAISCtx-MoreSelected())
852 {
853 if (myAISCtx-HasSelectedShape)
854 {
855 TopoDS_Shape ashape = myAISCtx-SelectedShape();
856 // to be able to use the picked shape
857             }
858 else
859 {
860 Handle_AIS_InteractiveObject aniobj = myAISCtx-Interactive();
861 // to be able to use the picked interactive object
862 }
72b7576f 866
bf62b306 867You 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:
868 * *AIS_InteractiveContext::EraseSelected* erases the selected objects;
869 * *AIS_InteractiveContext::DisplaySelected* displays them;
870 * *AIS_InteractiveContext::SetSelected* puts the objects in the list of selections;
871 * *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;
872 * *AIS_InteractiveContext::AddOrRemoveSelected* adds or removes an object from the list of selected entities;
873 * *AIS_InteractiveContext::HilightSelected* highlights the selected object;
874 * *AIS_InteractiveContext::UnhilightSelected* removes highlighting from the selected object;
875 * *AIS_InteractiveContext::ClearSelected* empties the list of selected objects.
72b7576f 876
72b7576f 877
bf62b306 878You can highlight and remove highlighting from a current object, and empty the list of current objects using the following functions:
880 AIS_InteractiveContext::HilightCurrents
881 AIS_InteractiveContext::UnhilightCurrents
882 AIS_InteractiveContext::ClearCurrents
884When you are in an open Local Context, you may need to keep "temporary" interactive objects. This is possible using the following functions:
885 * *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.
886 * *AIS_InteractiveContext::SetSelectedCurrent* allows the selected object to become the current object when you close the local context.
72b7576f 887
bf62b306 888You 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).
72b7576f 889
bf62b306 890@subsubsection occt_visu_3_4_7 Recommendations
72b7576f 891
bf62b306 892The possibilities of use for local contexts are numerous depending on the type of operation that you want to perform:
72b7576f 893 * working on all visualized interactive objects,
894 * working on only a few objects,
895 * working on a single object.
bf62b306 897When 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:
72b7576f 898
bf62b306 899~~~~~
900AIS_InteractiveContext::DisplayedObjects (AIS_ListOfInteractive& aListOfIO) const;
901AIS_InteractiveContext::DisplayedObjects (const AIS_KindOfInteractive WhichKind, const Standard_Integer WhichSignature;
902AIS_ListOfInteractive& aListOfIO) const;
72b7576f 904
bf62b306 905At this stage, you only have to load the functions *Load, Activate,* and so on.
72b7576f 906
bf62b306 907When you open a Local Context with default options, you must keep the following points in mind:
908* 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.
909* The Shape Type Interactive Objects are automatically decomposed into sub-shapes when standard activation modes are launched.
910* 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.
72b7576f 911
bf62b306 912The stages could be the following:
913 1. Open a Local Context with the right options;
914 2. Load/Visualize the required complementary objects with the desired activation modes.
915 3. Activate Standard modes if necessary
916 4. Create its filters and add them to the Local Context
917 5. Detect/Select/recover the desired entities
918 6. Close the Local Context with the adequate index.
72b7576f 919
bf62b306 920It 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.
922Let us assume that you have visualized several types of interactive objects: *AIS_Points*, *AIS_Axes*, *AIS_Trihedrons*, and *AIS_Shapes*.
72b7576f 923
bf62b306 924For your applicative function, you need an axis to create a revolved object. You could obtain this axis by identifying:
72b7576f 925 * an axis which is already visualized,
926 * 2 points,
927 * a rectilinear edge on the shapes which are present,
bf62b306 928 * a cylindrical face on the shapes (You will take the axis of this face)
72b7576f 929
bf62b306 930~~~~~
932 (const Handle(AIS_InteractiveContext)& Ctx,
933  ....) :
934  myCtx(Ctx),
935 ...
72b7576f 936{
bf62b306 941myIndex =myCtx-OpenLocalContext();
72b7576f 942
bf62b306 943//the filters
72b7576f 944
bf62b306 945Handle(AIS_SignatureFilter) F1 = new  AIS_SignatureFilter(AIS_KOI_Datum,AIS_SD_Point);
946//filter on the points
72b7576f 947
bf62b306 948Handle(AIS_SignatureFilter) F2 = new AIS_SignatureFilter(AIS_KOI_Datum,AIS_SD_Axis);
949//filters on the axes.
72b7576f 950
bf62b306 951Handle(StdSelect_FaceFilter) F3 = new StdSelect_FaceFilter(AIS_Cylinder);
952//cylindrical face filters
72b7576f 953//...
bf62b306 954// activation of standard modes on the shapes..
72b7576f 955myCtx-ActivateStandardMode(TopAbs_FACE);
bf62b306 959myCTX-Add(F3);
72b7576f 960
bf62b306 961// at this point, you can call the selection/detection function
72b7576f 962}
964void myIHMEditor::MoveTo(xpix,ypix,Vue)
bf62b306 966{ myCTX-MoveTo(xpix,ypix,vue);
967// the highlight of what is detected is automatic.
969Standard_Boolean myIHMEditor::Select()
971// returns true if you should continue the selection
972 myCTX-Select();
973 myCTX-InitSelected();
974 if(myCTX-MoreSelected())
975  {
976  if(myCTX-HasSelectedShape())
977 { const TopoDS_Shape& sh = myCTX-SelectedShape();
978 if( vertex){
979 if(myFirstV...)
980 {
981 //if it’s the first vertex, you stock it, then you deactivate the faces and only keep the filter on the points:
982 mypoint1 = ....;
983 myCtx-RemoveFilters();
984 myCTX-DeactivateStandardMode(TopAbs_FACE);
985 myCtx-Add(F1);
986 // the filter on the AIS_Points
987 myFirstV = Standard_False;
988 return Standard_True;
989  }
990 else
991  {
992 mypoint2 =...;
993 // construction of the axis return Standard_False;
994 }
995  }
996  else
997   {
998 //it is a cylindrical face : you recover the axis; visualize it; and stock it.
999 return Standard_False;
1000 }
1001   }
1002 // it is not a shape but is no doubt a point.
1003 else
1004 {
1005 Handle(AIS_InteractiveObject)
1006 SelObj = myCTX-SelectedInteractive();
1007 if(SelObj-Type()==AIS_KOI_Datum)
1008 {
1009 if(SelObj-Signature()==1)
1010 {
1011 if (firstPoint)
1012 {
1013 mypoint1 =...
1014 return Standard_True;
1015 }
1016 else
1017 {
1018 mypoint2 = ...;
1019 //construction of the axis, visualization, stocking
1020 return Standard_False;
1021 }
1022 }
1024 else
1025 {
1026 // you have selected an axis; stock the axis
1027 return Standard_False;
1028 }
1029 }
1030 }
1031 }
1032 }
1033void myIHMEditor::Terminate()
72b7576f 1039
bf62b306 1040@subsection occt_visu_3_5 Standard Interactive Object Classes
72b7576f 1041
bf62b306 1042@subsubsection occt_visu_3_5_1 Datums
1044*AIS_Point, AIS_Axis, AIS_Line, AIS_Circle, AIS_Plane* and *AIS_Trihedron* have four selection modes:
1045 * mode 0 : selection of a trihedron;
1046 * mode 1 : selection of the origin of the trihedron;
1047 * mode 2 : selection of the axes;
1048 * mode 3 : selection of the planes XOY, YOZ, XOZ.
72b7576f 1049
bf62b306 1050when you activate one of modes: 1 2 3 4, you pick AIS objects of type:
1051 * *AIS_Point*
1052 * *AIS_Axis* (and information on the type of axis)
1053 * *AIS_Plane* (and information on the type of plane).
72b7576f 1054
bf62b306 1055*AIS_PlaneTrihedron* offers three selection modes:
1056 * mode 0 : selection of the whole trihedron;
1057 * mode 1 : selection of the origin of the trihedron;
1058 * mode 2 : selection of the axes - same remarks as for the Trihedron.
72b7576f 1059
bf62b306 1060For 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.
e5bd0d98 1061
bf62b306 1062@subsubsection occt_visu_3_5_2 Objects
e5bd0d98 1063
ba06f8bb 1064*AIS_Shape* has three visualization modes :
72b7576f 1065 * mode 0 : Line (default mode)
1066 * mode 1 : Shading (depending on the type of shape)
1067 * mode 2 : Bounding Box
ba06f8bb 1069And at maximum seven selection modes, depending on the shape complexity:
bf62b306 1070 * mode 0 : selection of the *AIS_Shape*;
1071 * mode 1 : selection of the vertices;
1072 * mode 2 : selection of the edges;
1073 * mode 3 : selection of the wires;
1074 * mode 4 : selection of the faces;
1075 * mode 5 : selection of the shells;
e5bd0d98 1076 * mode 6 : selection of the constituent solids.
72b7576f 1077
ba06f8bb 1078 * *AIS_Triangulation* is a simple interactive object for displaying triangular mesh contained in *Poly_Triangulation* container.
1079 * *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.
1080 * *AIS_ConnectedShape* is an object connected to interactive objects having a shape; this class has the same decompositions as *AIS_Shape*. What’s more, it allows a presentation of hidden parts, which are calculated automatically from the shape of its reference.
1081 * *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)
1082 * *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.
1083 * *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.
1084 * *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.
72b7576f 1085
bf62b306 1086@subsubsection occt_visu_3_5_3 Relations
1087 * *AIS_ConcentricRelation*
1088 * *AIS_FixRelation*
1089 * *AIS_IdenticRelation*
1090 * *AIS_ParallelRelation*
1091 * *AIS_PerpendicularRelation*
1092 * *AIS_Relation*
1093 * *AIS_SymmetricRelation*
1094 * *AIS_TangentRelation*
72b7576f 1095
bf62b306 1096The list of relations is not exhaustive.
72b7576f 1097
bf62b306 1098@subsubsection occt_visu_3_5_4 Dimensions
1099 * *AIS_AngleDimension*
1100 * *AIS_Chamf3dDimension*
1101 * *AIS_DiameterDimension*
1102 * *AIS_DimensionOwner*
1103 * *AIS_LengthDimension*
1104 * *AIS_OffsetDimension*
1105 * *AIS_RadiusDimension*
72b7576f 1106
bf62b306 1107 @subsubsection occt_visu_3_5_5 MeshVS_Mesh
72b7576f 1108
bf62b306 1109*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.
72b7576f 1110
bf62b306 1111However, 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.
72b7576f 1112
bf62b306 1113The 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.
72b7576f 1114
72b7576f 1115You can add/remove builders using the following methods:
bf62b306 1116~~~~~
1117 MeshVS_Mesh::AddBuilder (const Handle (MeshVS_PrsBuilder) &Builder, Standard_Boolean TreatAsHilighter)
1118 MeshVS_Mesh::RemoveBuilder (const Standard_Integer Index)
1119 MeshVS_Mesh::RemoveBuilderById (const Standard_Integer Id)
72b7576f 1121
bf62b306 1122There 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:
1124 MeshVS_DMF_WireFrame
1125 MeshVS_DMF_Shading
1126 MeshVS_DMF_Shrink
72b7576f 1128
bf62b306 1129It is also possible to display deformed mesh in wireframe, shading or shrink modes usung :
1131 MeshVS_DMF_DeformedPrsWireFrame
1132 MeshVS_DMF_DeformedPrsShading
1133 MeshVS_DMF_DeformedPrsShrink
72b7576f 1135
bf62b306 1136The following methods represent different kinds of data :
1138 MeshVS_DMF_VectorDataPrs
1139 MeshVS_DMF_NodalColorDataPrs
1140 MeshVS_DMF_ElementalColorDataPrs
1141 MeshVS_DMF_TextDataPrs
1142 MeshVS_DMF_EntitiesWithData
1145The following methods provide selection and highlighting :
1147 MeshVS_DMF_SelectionPrs
1148 MeshVS_DMF_HilightPrs
72b7576f 1150
bf62b306 1151*MeshVS_DMF_User* is a user-defined mode.
72b7576f 1152
bf62b306 1153These values will be used by the presentation builder.
1154There is also a set of selection modes flags that can be grouped in a combination of bits:
1155 * *MeshVS_SMF_0D*
1156 * *MeshVS_SMF_Link*
1157 * *MeshVS_SMF_Face*
1158 * *MeshVS_SMF_Volume*
1159 * *MeshVS_SMF_Element* - groups *0D, Link, Face* and *Volume* as a bit mask ;
1160 * *MeshVS_SMF_Node*
1161 * *MeshVS_SMF_All* - groups *Element* and *Node* as a bit mask;
1162 * *MeshVS_SMF_Mesh*
1163 * *MeshVS_SMF_Group*
1165Such an object, for example, can be used for displaying the object and stored in the STL file format:
72b7576f 1166
bf62b306 1167~~~~~
1168// read the data and create a data source
1169Handle (StlMesh_Mesh) aSTLMesh = RWStl::ReadFile (aFileName);
1170Handle (XSDRAWSTLVRML_DataSource) aDataSource = new XSDRAWSTLVRML_DataSource (aSTLMesh);
72b7576f 1171
bf62b306 1172// create mesh
1173Handle (MeshVS_Mesh) aMesh = new MeshVS();
1174aMesh-SetDataSource (aDataSource);
72b7576f 1175
bf62b306 1176// use default presentation builder
1177Handle (MeshVS_MeshPrsBuilder) aBuilder = new MeshVS_MeshPrsBuilder (aMesh);
1178aMesh-AddBuilder (aBuilder, Standard_True);
72b7576f 1180
bf62b306 1181*MeshVS_NodalColorPrsBuilder* allows representing a mesh with a color scaled texture mapped on it.
1182To do this you should define a color map for the color scale, pass this map to the presentation builder,
1183and define an appropriate value in the range of 0.0 – 1.0 for every node.
72b7576f 1184
bf62b306 1185The following example demonstrates how you can do this (check if the view has been set up to display textures):
1188// assign nodal builder to the mesh
1189Handle (MeshVS_NodalColorPrsBuilder) aBuilder = new MeshVS_NodalColorPrsBuilder
1190    (aMesh,MeshVS_DMF_NodalColorDataPrs | MeshVS_DMF_OCCMask);
1191aBuilder-UseTexture (Standard_True);
1193// prepare color map
1194Aspect_SequenceOfColor aColorMap;
1195aColorMap.Append ((Quantity_NameOfColor) Quantity_NOC_RED);
1196aColorMap.Append ((Quantity_NameOfColor) Quantity_NOC_BLUE1);
1198// assign color scale map values (0..1) to nodes
1199TColStd_DataMapOfIntegerReal aScaleMap;
1201// iterate through the nodes and add an node id and an appropriate value to the map
1202aScaleMap.Bind (anId, aValue);
1204// pass color map and color scale values to the builder
1205aBuilder-SetColorMap (aColorMap);
1206aBuilder-SetInvalidColor (Quantity_NOC_BLACK);
1207aBuilder-SetTextureCoords (aScaleMap);
1208aMesh-AddBuilder (aBuilder, Standard_True);
72b7576f 1210
bf62b306 1211@subsection occt_visu_3_6 Dynamic Selection
72b7576f 1212
bf62b306 1213The 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.
1214To 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.
72b7576f 1215
bf62b306 1216@subsubsection occt_visu_3_6_1 How to go from the objects to 2D boxes
72b7576f 1217
bf62b306 1219An 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.
72b7576f 1220
bf62b306 1221The sensitive primitive is capable of:
72b7576f 1222 * giving a 2D bounding box to the selector.
bf62b306 1223 * answering the rejection criteria positively or negatively by a "Matches" function.
72b7576f 1224 * being projected from 3D in the 2D space of the view if need be.
bf62b306 1225 * returning the owner which it will represent in terms of selection.
72b7576f 1226
bf62b306 1227A set of standard sensitive primitives exists in Select3D packages for 3D primitives.
72b7576f 1228
bf62b306 1229The 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.
72b7576f 1230
bf62b306 1231@image html visualization_image021.png
1232@image latex visualization_image021.png
72b7576f 1233
bf62b306 1234@subsubsection occt_visu_3_6_2 Implementation in an interactive/selectable object
1236Define the number of selection modes possible, i.e. what you want to identify by activating each of the selection modes.
72b7576f 1237
bf62b306 1238For example: for an interactive object representing a topological shape:
1239* mode 0: selection of the interactive object itself;
1240* mode 1: selection of the vertices;
1241* mode 2: selection of the edges;
1242* mode 3: selection of the wires;
1243* mode 4: selection of the detectable faces.
72b7576f 1244
bf62b306 1245For each selection mode of an interactive object, "model" is the set of entities, which you want to locate by these primitives and these owners.
72b7576f 1246
bf62b306 1247There 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.
72b7576f 1248
bf62b306 1249The set of sensitive primitives which has been calculated for a given mode is stocked in *SelectMgr_Selection*.
72b7576f 1250
bf62b306 1251For an Interactive object, the modeling is done in the *ComputeSelection* virtual function.
72b7576f 1252
bf62b306 1253Let us consider an example of an interactive object representing a box.
72b7576f 1254
bf62b306 1255We are interested in two location modes:
1256 * mode 0: location of the whole box.
1257 * mode 1: location of the edges on the box.
72b7576f 1258
bf62b306 1259For 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*.
1261The *ComputeSelection* function for the interactive box can have the following form:
72b7576f 1262
bf62b306 1263~~~~~
1264void InteractiveBox::ComputeSelection
1265 (const Handle(SelectMgr_Selection)& Sel,
1266  const Standard_Integer Mode)
1268 switch(Mode)
1269 { case 0: //locating the whole box by making its faces sensitive...
1270 {
1271 Handle(SelectMgr_EntityOwner) Ownr = new SelectMgr_EntityOwner(this,5);
1272 for(Standard_Integer I=1;I=Nbfaces;I++)
1273 {
1274 //Array is a TColgp_Array1OfPnt: which represents the array of vertices. Sensitivity is
1275 Select3D_TypeOfSensitivity value
1276 Sel-Add(new
1278 }
1279 break;
1280    }
1281   case 1:
1282 // locates the edges {
1283 for(Standard_Integer i=1;i=12;i++)
1284 {
1285 // 1 owner per edge...
1286 Handle(mypk_EdgeOwner) Ownr =
1287 new mypk_EdgeOwner(this,i,6);
1288 //6-priority
1289 Sel-Add(new Select3D_SensitiveSegment (Ownr,firstpt(i),lastpt(i)));
1290 }
1291 break;
1292 }
1293 }
1294 }
72b7576f 1296
bf62b306 1297Selectable 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.
72b7576f 1298
bf62b306 1299NOTE: This procedure is completely hidden if you use the <a href="#occt_visu_3_3"> AIS Interactive Context </a>
72b7576f 1300
1301<h4>Example </h4>
bf62b306 1302~~~~~
1303//We have several " interactive boxes " box1, box2, box3;
1304 Handle(SelectMgr_SelectionManager) SM = new SelectMgr_SelectionManager();
1305 Handle(StdSelect_ViewerSelector3d) VS = new StdSelect_ViewerSelector3d();
1306 SM-Add(VS);
1307 SM-Load(box1);SM-Load(box2);SM-Load(box3);
1308 // box load.
1309 SM-Activate(box1,0,VS);
1310 // activates mode 0 of box 1 in the selector VS
1311 SM-Activate(box1,1,VS);
1312 M-Activate(box3,1,VS);
1314// detection of primitives by mouse position.
1315Handle(EntityOwner) POwnr = VS-OnePicked();
1316// picking of the "best" owner detected
1318 {
1319 VS-Picked();
1320 // picking of all owners detected
1321   }
1322 SM-Deactivate(box1);
1323 // deactivate all active modes of box1
72b7576f 1325
bf62b306 1326@section occt_visu_4 3D Presentations
72b7576f 1327
bf62b306 1328@subsection occt_visu_4_1 Glossary of 3D terms
72b7576f 1329
bf62b306 1330* **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.
1331* **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.
1332* **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.
1333* **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.
1334* **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.
1335* **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.
1336* **View** - is defined by a view orientation, a view mapping, and a context view.
1337* **Viewer** - manages a set of views.
1338* **View orientation** - defines the manner in which the observer looks at the scene in terms of View Reference Coordinates.
1339* **View mapping** - defines the transformation from View Reference Coordinates to the Normalized Projection Coordinates. This follows the Phigs scheme.
1340* **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.
72b7576f 1341
bf62b306 1342@subsection occt_visu_4_2 Creating a 3D scene
72b7576f 1343
bf62b306 1344To create 3D graphic objects and display them on the screen, follow the procedure below:
13451. Create attributes.
13462. Create a 3D viewer..
13473. Create a view.
13484. Create an interactive context.
13495. Create interactive objects.
13506. Create primitives in the interactive object
13517. Display the interactive object.
72b7576f 1352
bf62b306 1353@subsubsection occt_visu_4_2_1 Create attributes
72b7576f 1354
bf62b306 1355Create colors.
72b7576f 1356
bf62b306 1357~~~~~
1358Quantity_Color Black (Quantity_NOC_BLACK);
1359Quantity_Color Blue (Quantity_NOC_MATRABLUE);
1360Quantity_Color Brown (Quantity_NOC_BROWN4);
1361Quantity_Color Firebrick (Quantity_NOC_FIREBRICK);
1362Quantity_Color Forest (Quantity_NOC_FORESTGREEN);
1363Quantity_Color Gray (Quantity_NOC_GRAY70);
1364Quantity_Color MyColor (0.99, 0.65, 0.31, Quantity_TOC_RGB);
1365Quantity_Color Beet (Quantity_NOC_BEET);
1366Quantity_Color White (Quantity_NOC_WHITE);
72b7576f 1368
72b7576f 1369
bf62b306 1370Create line attributes.
72b7576f 1371
bf62b306 1372~~~~~
1373Handle(Graphic3d_AspectLine3d) CTXLBROWN = new Graphic3d_AspectLine3d ();
1374Handle(Graphic3d_AspectLine3d) CTXLBLUE = new Graphic3d_AspectLine3d ();
1375Handle(Graphic3d_AspectLine3d) CTXLWHITE = new Graphic3d_AspectLine3d();
1376 CTXLBROWN-SetColor (Brown);
1377 CTXLBLUE-SetColor (Blue);
1378 CTXLWHITE-SetColor (White);
72b7576f 1380
bf62b306 1381Create marker attributes.
1383Handle(Graphic3d_AspectMarker3d) CTXMFIREBRICK = new Graphic3d_AspectMarker3d();
1384 CTXMFIREBRICK-SetColor (Firebrick);
1385 CTXMFIREBRICK-SetScale (1.0);
72b7576f 1388
bf62b306 1389Create facet attributes.
1391Handle(Graphic3d_AspectFillArea3d) CTXF = new Graphic3d_AspectFillArea3d ();
1392Graphic3d_MaterialAspect BrassMaterial (Graphic3d_NOM_BRASS);
1393Graphic3d_MaterialAspect GoldMaterial (Graphic3d_NOM_GOLD);
1394 CTXF-SetInteriorStyle (Aspect_IS_SOLID);
1395 CTXF-SetInteriorColor (MyColor);
1396 CTXF-SetDistinguishOn ();
1397 CTXF-SetFrontMaterial (GoldMaterial);
1398 CTXF-SetBackMaterial (BrassMaterial);
1399 CTXF-SetEdgeOn ();
72b7576f 1401
bf62b306 1402Create text attributes.
1404Handle(Graphic3d_AspectText3d) CTXT = new Graphic3d_AspectText3d (Forest, Graphic3d_NOF_ASCII_MONO, 1., 0.);
72b7576f 1406
bf62b306 1407@subsubsection occt_visu_4_2_2 Create a 3D Viewer (a Windows example)
72b7576f 1408
bf62b306 1409~~~~~
1410Handle(Aspect_DisplayConnection) aDisplayConnection;
1411Handle(Graphic3d_GraphicDriver) aGraphicDriver = Graphic3d::InitGraphicDriver (aDisplayConnection);
1412TCollection_ExtendedString aName("3DV");
1413myViewer = new V3d_Viewer (aGraphicDriver,aName.ToExtString (), "");
1414myViewer - SetDefaultLights ();
1415myViewer - SetLightOn ();
72b7576f 1417
bf62b306 1418@subsubsection occt_visu_4_2_3 Create a 3D view (a Windows example)
72b7576f 1419
bf62b306 1420It is assumed that a valid Windows window may already be accessed via the method *GetSafeHwnd()*.
1422Handle (WNT_Window) aWNTWindow;
1423aWNTWindow = new WNT_Window (GetSafeHwnd());
1424myView = myViewer -> CreateView();
1425myView -> SetWindow (a WNTWindow);
72b7576f 1427
bf62b306 1428@subsubsection occt_visu_4_2_4 Create an interactive context
72b7576f 1429
bf62b306 1430~~~~~
1431myAISContext = new AIS_InteractiveContext (myViewer);
72b7576f 1433
bf62b306 1434You are now able to display interactive objects such as an *AIS_Shape*.
72b7576f 1435
bf62b306 1436~~~~~
1437TopoDS_Shape aShape = BRepAPI_MakeBox(10,20,30)_Solid();
1438Handle (AIS_Shape) aAISShape = new AIS_Shape(aShape);
1439myAISContext - Display (aAISShape);
72b7576f 1441
bf62b306 1442@subsubsection occt_visu_4_2_5 Create your own interactive object
72b7576f 1443
bf62b306 1444Follow the procedure below to compute the presentable object:
72b7576f 1445
bf62b306 14461. Build a presentable object inheriting from *AIS_InteractiveObject* (refer to the Chapter on Presentable Objects).
14472. Reuse the *Prs3d_Presentation* provided as an argument of the compute methods.
72b7576f 1448
bf62b306 1449**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.
72b7576f 1450
72b7576f 1451
bf62b306 1452Let us look at the example of compute methods
72b7576f 1453
bf62b306 1454~~~~~
1457 (const Handle(PrsMgr_PresentationManager3d)&
1458 aPresentationManager,
1459 const Handle(Prs3d_Presentation)& aPrs,
1460 const Standard_Integer aMode)
72b7576f 1464
bf62b306 1465void
1467 (const Handle(Prs3d_Projector)&,
1468 const Handle(Prs3d_Presentation)& aPrs)
72b7576f 1473
bf62b306 1474@subsubsection occt_visu_4_2_6 Create primitives in the interactive object
72b7576f 1475
bf62b306 1476Get the group used in *Prs3d_Presentation*.
72b7576f 1477
bf62b306 1478~~~~~
1479Handle(Graphic3d_Group) TheGroup = Prs3d_Root::CurrentGroup(aPrs);
72b7576f 1481
bf62b306 1482Update the group attributes.
72b7576f 1483
bf62b306 1484~~~~~
1485TheGroup - SetPrimitivesAspect(CTXLBLUE);
72b7576f 1487
bf62b306 1488Create two triangles in *TheGroup*.
72b7576f 1489
bf62b306 1490~~~~~
72b7576f 1491Standard_Integer aNbTria = 2;
bf62b306 1492Handle(Graphic3d_ArrayOfTriangles) aTriangles = new Graphic3d_ArrayOfTriangles(3 * aNbTria, 0, Standard_True);
72b7576f 1493Standard_Integer anIndex;
1494for (anIndex = 1; anIndex = aNbTria; nt++)
bf62b306 1496  aTriangles-AddVertex(anIndex * 5., 0., 0., 1., 1., 1.);
1497  aTriangles-AddVertex(anIndex * 5 + 5, 0., 0., 1., 1., 1.);
1498  aTriangles-AddVertex(anIndex * 5 + 2.5, 5., 0., 1., 1., 1.);
72b7576f 1499}
1500TheGroup-BeginPrimitives ();
1502TheGroup-EndPrimitives ();
bf62b306 1503~~~~~
72b7576f 1504
bf62b306 1505The *BeginPrimitives()* and *EndPrimitives()* methods are used when creating a set of various primitives in the same group.
1506Use the polyline function to create a boundary box for the *Struct* structure in group *TheGroup*.
72b7576f 1507
bf62b306 1508~~~~~
1509Standard_Real Xm, Ym, Zm, XM, YM, ZM;
1510Struct-MinMaxValues (Xm, Ym, Zm, XM, YM, ZM);
72b7576f 1511
bf62b306 1512Handle(Graphic3d_ArrayOfPolylines) aPolylines = new Graphic3d_ArrayOfPolylines(16, 4);
72b7576f 1513aPolylines-AddBound (4);
bf62b306 1514aPolylines-AddVertex (Xm, Ym, Zm);
1515aPolylines-AddVertex (Xm, Ym, ZM);
1516aPolylines-AddVertex (Xm, YM, ZM);
1517aPolylines-AddVertex (Xm, YM, Zm);
72b7576f 1518aPolylines-AddBound (4);
bf62b306 1519aPolylines-AddVertex (Xm, Ym, Zm);
1520aPolylines-AddVertex (XM, Ym, Zm);
1521aPolylines-AddVertex (XM, Ym, ZM);
1522aPolylines-AddVertex (XM, YM, ZM);
72b7576f 1523aPolylines-AddBound (4);
bf62b306 1524aPolylines-AddVertex (XM, YM, Zm);
1525aPolylines-AddVertex (XM, Ym, Zm);
1526aPolylines-AddVertex (XM, YM, Zm);
1527aPolylines-AddVertex (Xm, YM, Zm);
72b7576f 1528aPolylines-AddBound (4);
bf62b306 1529aPolylines-AddVertex (Xm, YM, ZM);
1530aPolylines-AddVertex (XM, YM, ZM);
1531aPolylines-AddVertex (XM, Ym, ZM);
1532aPolylines-AddVertex (Xm, Ym, ZM);
72b7576f 1533
bf62b306 1534TheGroup-BeginPrimitives ();
72b7576f 1535TheGroup-AddPrimitiveArray(aPolylines);
bf62b306 1536TheGroup-EndPrimitives ();
72b7576f 1538
bf62b306 1539Create text and markers in group *TheGroup*.
72b7576f 1540
bf62b306 1541~~~~~
1542static char *texte[3] = {  "Application title",
1543 "My company",
1544 "My company address." };
1545Graphic3d_Array1OfVertex Tpts8 (0, 1);
1546Tpts8(0).SetCoord (-40.0, -40.0, -40.0);
1547Tpts8(1).SetCoord (40.0, 40.0, 40.0);
1548TheGroup-MarkerSet (Tpts8);
1549Graphic3d_Vertex Marker (0.0, 0.0, 0.0);
1551for (i=0; i=2; i++) {
1552  Marker.SetCoord (-(Standard_Real)i*4 + 30,
1553                    (Standard_Real)i*4,
1554                   -(Standard_Real)i*4);
1555  TheGroup-Text (texte[i], Marker, 20.);
72b7576f 1558
bf62b306 1559@section occt_visu_5 3D Resources
72b7576f 1560
bf62b306 1561The 3D resources include the *Graphic3d* and *V3d* packages.
72b7576f 1562
bf62b306 1563@subsection occt_visu_5_1 Graphic3D Package
72b7576f 1564
bf62b306 1565@subsubsection occt_visu_5_1_1 Overview
72b7576f 1566
bf62b306 1567The *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. 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.
72b7576f 1568
bf62b306 1569@subsubsection occt_visu_5_1_2 Provided services
72b7576f 1570
bf62b306 1571Graphic structures can be:
72b7576f 1572 * Displayed,
1573 * Highlighted,
1574 * Erased,
1575 * Transformed,
1576 * Connected to form a tree.
bf62b306 1577
1578There are classes for:
72b7576f 1579 * Visual attributes for lines, faces, markers, text, materials,
1580 * Vectors and vertices,
72b7576f 1581 * Graphic objects, groups, and structures.
bf62b306 1583@subsubsection occt_visu_5_1_3 About the primitives
1585* **Markers**
72b7576f 1586 * Have one or more vertices,
1587 * Have a type, a scale factor, and a color,
bf62b306 1588 * Have a size, shape, and orientation independent of transformations.
1589* **Polygons**
72b7576f 1590 * Have one closed boundary,
1591 * Have at least three vertices,
1592 * Are planar and have a normal,
bf62b306 1593 * Have interior attributes - style, color, front and back material, texture and reflection ratio,
1594 * Have a boundary with the following attributes - type, width scale factor, color. The boundary is only drawn when the interior style is hollow.
72b7576f 1595
bf62b306 1596* **Polygons with holes**
1597 * Have multiple closed boundaries, each one with at least three vertices,
72b7576f 1598 * Are planar and have a normal,
bf62b306 1599 * Have interior attributes - style, color, front and back material,
1600 * Have a boundary with the following attributes - type, width scale factor, color. The boundary is only drawn when the interior style is hollow.
72b7576f 1601
bf62b306 1602* **Polylines**
72b7576f 1603 * Have two or more vertices,
1604 * Have the following attributes - type, width scale factor, color.
bf62b306 1606* **Text**
72b7576f 1607 * Has geometric and non-geometric attributes,
bf62b306 1608 * Geometric attributes - character height, character up vector, text path, horizontal and vertical alignment, orientation, three-dimensional position, zoomable flag
1609 * Non-geometric attributes - text font, character spacing, character expansion factor, color.
72b7576f 1610
bf62b306 1611@subsubsection occt_visu_5_1_4 Primitive arrays
72b7576f 1612
bf62b306 1613Primitive 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.
72b7576f 1614
bf62b306 1615The 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.
72b7576f 1616
bf62b306 1617The 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:
1619The following example shows how to disable the VBO support:
72b7576f 1620
bf62b306 1621~~~~~
1622*// get the graphic driver*
1623Handle (Graphic3d_GraphicDriver) aDriver =
1624  myAISContext-CurrentViewer()-Driver();
72b7576f 1625
bf62b306 1626*// disable VBO support*
1627aDriver-EnableVBO (Standard_False);
72b7576f 1629
bf62b306 1630**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*.
1632The different types of primitives could be presented with the following primitive arrays:
1633 * *Graphic3d_ArrayOfPoints,*
1634 * *Graphic3d_ArrayOfPolygons,*
1635 * *Graphic3d_ArrayOfPolylines,*
1636 * *Graphic3d_ArrayOfQuadrangles,*
1637 * *Graphic3d_ArrayOfQuadrangleStrips,*
1638 * *Graphic3d_ArrayOfSegments,*
1639 * *Graphic3d_ArrayOfTriangleFans,*
1640 * *Graphic3d_ArrayOfTriangles,*
1641 * *Graphic3d_ArrayOfTriangleStrips.*
1643The *Graphic3d_ArrayOfPrimitives* is a base class for these primitive arrays.
1645Method *Graphic3d_ArrayOfPrimitives::AddVertex* allows adding There is a set of similar methods to add vertices to the primitive array.
1647These 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.
1649You can also modify the values assigned to the vertex or query these values by the vertex index:
1650 * *void Graphic3d_ArrayOfPrimitives::SetVertice*
1651 * *void Graphic3d_ArrayOfPrimitives::SetVertexColor*
1652 * *void Graphic3d_ArrayOfPrimitives::SetVertexNormal*
1653 * *void Graphic3d_ArrayOfPrimitives::SetVertexTexel*
1654 * *gp_Pnt Graphic3d_ArrayOfPrimitives::Vertices*
1655 * *gp_Dir  Graphic3d_ArrayOfPrimitives::VertexNormal*
1656 * *gp_Pnt3d Graphic3d_ArrayOfPrimitives::VertexTexel*
1657 * *Quantity_Color Graphic3d_ArrayOfPrimitives::VertexColor*
1658 * *void Graphic3d_ArrayOfPrimitives::Vertices*
1659 * *void Graphic3d_ArrayOfPrimitives::VertexNormal*
1660 * *void Graphic3d_ArrayOfPrimitives::VertexTexel*
1661 * *void Graphic3d_ArrayOfPrimitives::VertexColor*
1663The following example shows how to define an array of points:
72b7576f 1664
bf62b306 1665~~~~~
1666// create an array
1667Handle (Graphic3d_ArrayOfPoints) anArray = new Graphic3d_ArrayOfPoints (aVerticiesMaxCount);
1669// add vertices to the array
1670anArray-AddVertex (10.0, 10.0, 10.0);
1671anArray-AddVertex (0.0, 10.0, 10.0);
72b7576f 1672
bf62b306 1673// add the array to the structure
1674Handle (Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (aPrs);
72b7576f 1675aGroup-BeginPrimitives ();
1676aGroup-AddPrimitiveArray (anArray);
1677aGroup-EndPrimitives ();
bf62b306 1678~~~~~
72b7576f 1679
bf62b306 1680If the primitives share the same vertices (polygons, triangles, etc.) then you can define them as indices of the vertices array.
72b7576f 1681
bf62b306 1682The 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.
72b7576f 1683
bf62b306 1684It is also possible to query the vertex defined by an edge using method *Graphic3d_ArrayOfPrimitives::Edge*
72b7576f 1685
bf62b306 1686The following example shows how to define an array of triangles:
72b7576f 1687
bf62b306 1688~~~~~
1689// create an array
1690Standard_Boolean IsNormals     = Standard_False;
1691Standard_Boolean IsColors      = Standard_False;
1692Standard_Boolean IsTextureCrds = Standard_False;
1693Handle (Graphic3d_ArrayOfTriangles) anArray =
1694          new Graphic3d_ArrayOfTriangles (aVerticesMaxCount,
1695                                          aEdgesMaxCount,
1696                                          IsNormals,
1697                                          IsColors,
1698                                          IsTextureCrds);
1699// add vertices to the array
1700anArray-AddVertex (-1.0, 0.0, 0.0);   // vertex 1
1701anArray-AddVertex ( 1.0, 0.0, 0.0);   // vertex 2
1702anArray-AddVertex ( 0.0, 1.0, 0.0);   // vertex 3
1703anArray-AddVertex ( 0.0,-1.0, 0.0);   // vertex 4
1705// add edges to the array
1706anArray-AddEdge (1);  // first triangle
1707anArray-AddEdge (2);
1708anArray-AddEdge (3);
1709anArray-AddEdge (1);  // second triangle
1710anArray-AddEdge (2);
1711anArray-AddEdge (4);
1713// add the array to the structure
1714Handle (Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (aPrs);
1715aGroup-BeginPrimitives ();
1716aGroup-AddPrimitiveArray (anArray);
1717aGroup-EndPrimitives ();
72b7576f 1719
bf62b306 1720If 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.
72b7576f 1721
bf62b306 1722It is also possible to set the color and query the number of edges in the bound and bound color.
1724 Standard_Integer Graphic3d_ArrayOfPrimitives::Bound
1725 Quantity_Color Graphic3d_ArrayOfPrimitives::BoundColor
1726 void Graphic3d_ArrayOfPrimitives::BoundColor
1729The following example shows how to define an array of polygons:
72b7576f 1730
bf62b306 1731~~~~~
1732// create an array
1733Standard_Boolean IsNormals      = Standard_False;
1734Standard_Boolean IsVertexColors = Standard_False;
1735Standard_Boolean IsFaceColors   = Standard_False;
1736Standard_Boolean IsTextureCrds  = Standard_False;
1737Handle (Graphic3d_ArrayOfPolygons) anArray =
1738          new Graphic3d_ArrayOfPolygons (aVerticesMaxCount,
1739                                         aBoundsMaxCount,
1740                                         aEdgesMaxCount,
1741                                         IsNormals,
1742                                         IsVertexColors,
1743                                         IsFaceColors,
1744                                         IsTextureCrds);
1746// add bounds to the array, first polygon
1747anArray-AddBound (3);
1748anArray-AddVertex (-1.0, 0.0, 0.0);  
1749anArray-AddVertex ( 1.0, 0.0, 0.0);  
1750anArray-AddVertex ( 0.0, 1.0, 0.0);  
1752// add bounds to the array, second polygon
72b7576f 1753anArray-AddBound (4);
bf62b306 1754anArray-AddVertex (-1.0, 0.0, 0.0);  
1755anArray-AddVertex ( 1.0, 0.0, 0.0);  
1756anArray-AddVertex ( 1.0,-1.0, 0.0);  
1757anArray-AddVertex (-1.0,-1.0, 0.0);  
1759// add the array to the structure
1760Handle (Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (aPrs);
1761aGroup-BeginPrimitives ();
1762aGroup-AddPrimitiveArray (anArray);
1763aGroup-EndPrimitives ();
72b7576f 1765
bf62b306 1766There are also several helper methods. You can get the type of the primitive array:
1768 Graphic3d_TypeOfPrimitiveArray
1769 Graphic3d_ArrayOfPrimitives::Type
1770 Standard_CString Graphic3d_ArrayOfPrimitives::StringType
72b7576f 1772
bf62b306 1773and check if the primitive array provides normals, vertex colors and vertex texels (texture coordinates):
72b7576f 1774
bf62b306 1775~~~~~
1776 Standard_Boolean Graphic3d_ArrayOfPrimitives::HasVertexNormals
1777 Standard_Boolean Graphic3d_ArrayOfPrimitives::HasVertexColors
1778 Standard_Boolean Graphic3d_ArrayOfPrimitives::HasVertexTexels
72b7576f 1780or get the number of vertices, edges and bounds:
bf62b306 1781~~~~~
1782 Standard_Integer Graphic3d_ArrayOfPrimitives::VertexNumber
1783 Standard_Integer Graphic3d_ArrayOfPrimitives::EdgeNumber
1784 Standard_Integer Graphic3d_ArrayOfPrimitives::BoundNumber
1787@subsubsection occt_visu_5_1_5 Materials
72b7576f 1788
bf62b306 1789A *material* is defined by :
72b7576f 1790 * Transparency,
bf62b306 1791 * Diffuse reflection - a component of the object color;
1792 * Ambient reflection;
1793 * Specular reflection - a component of the color of the light source.
72b7576f 1794
bf62b306 1795The following items are required to determine the three colors of reflection:
72b7576f 1796 * Color,
1797 * Coefficient of diffuse reflection,
1798 * Coefficient of ambient reflection,
1799 * Coefficient of specular reflection.
bf62b306 1801@subsubsection occt_visu_5_1_6 Textures
72b7576f 1802
bf62b306 1803A *texture* is defined by a name.
1804Three types of texture are available:
72b7576f 1805 * 1D,
1806 * 2D,
1807 * Environment mapping.
bf62b306 1809@subsubsection occt_visu_5_1_7 Graphic3d text
72b7576f 1810
bf62b306 1811The 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.
1812*Graphic3d* text primitives have the following features:
72b7576f 1813 * fixed size (non-zoomable) or zoomable,
1814 * can be rotated to any angle in the view plane,
1815 * support unicode charset.
bf62b306 1817The text attributes for the group could be defined with the *Graphic3d_AspectText3d* attributes group.
1818To add any text to the graphic structure you can use the following methods:
1820 void Graphic3d_Group::Text
1821 (const Standard_CString AText,
1822  const Graphic3d_Vertex& APoint,
1823  const Standard_Real AHeight,
1824  const Quantity_PlaneAngle AAngle,
1825  const Graphic3d_TextPath ATp,
1826  const Graphic3d_HorizontalTextAlignment AHta,
1827  const Graphic3d_VerticalTextAlignment AVta,
1828  const Standard_Boolean EvalMinMax),
1830*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).
1832*ATp* parameter defines the text path, *AHta* is the horizontal alignment of the text, *AVta* is the vertical alignment of the text.
1834You can pass *Standard_False* as *EvalMinMax* if you don’t want the graphic3d structure boundaries to be affected by the text position.
1836**Note** that the text orientation angle can be defined by *Graphic3d_AspectText3d* attributes.
1838 void Graphic3d_Group::Text
1839 (const Standard_CString AText,
1840  const Graphic3d_Vertex& APoint,
1841  const Standard_Real AHeight,
1842  const Standard_Boolean EvalMinMax)
1843 void Graphic3d_Group::Text
1844 (const TCcollection_ExtendedString &AText,
1845 const Graphic3d_Vertex& APoint,
1846  const Standard_Real AHeight,
1847  const Quantity_PlaneAngle AAngle,
1848  const Graphic3d_TextPath ATp,
1849  const Graphic3d_HorizontalTextAlignment AHta,
1850  const Graphic3d_VerticalTextAlignment AVta,
1851  const Standard_Boolean EvalMinMax)
1852 void Graphic3d_Group::Text
1853 (const TCcollection_ExtendedString &AText,
1854  const Graphic3d_Vertex& APoint,
1855  const Standard_Real AHeight,
1856  const Standard_Boolean EvalMinMax)
72b7576f 1858
bf62b306 1859See the example:
1861// get the group
1862Handle (Graphic3d_Group) aGroup = Prs3d_Root::CurrentGroup (aPrs);
72b7576f 1863
bf62b306 1864// change the text aspect
1865Handle(Graphic3d_AspectText3d) aTextAspect = new Graphic3d_AspectText3d ();
1866aTextAspect-SetTextZoomable (Standard_True);
1867aTextAspect-SetTextAngle (45.0);
1868aGroup-SetPrimitivesAspect (aTextAspect);
72b7576f 1869
bf62b306 1870// add a text primitive to the structure
72b7576f 1871Graphic3d_Vertex aPoint (1, 1, 1);
bf62b306 1872aGroup-Text (Standard_CString ("Text"), aPoint, 16.0);
1875@subsubsection occt_visu_5_1_8 Display priorities
72b7576f 1876
bf62b306 1877Structure display priorities control the order in which structures are drawn. When you display a structure you specify its priority. The lower the value, the lower the display priority. When the display is regenerated the structures with the lowest priority are drawn first. For structures with the same display priority the order in which they were displayed determines the drawing order. OCCT supports eleven structure display priorities.
72b7576f 1878
bf62b306 1879@subsubsection occt_visu_5_1_9 About structure hierarchies
72b7576f 1880
bf62b306 1881The 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.
72b7576f 1882
bf62b306 1883@subsection occt_visu_5_2 V3d Package
72b7576f 1884
bf62b306 1885@subsubsection occt_visu_5_2_1 Overview
72b7576f 1886
bf62b306 1887The *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.
72b7576f 1888
bf62b306 1889A 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.
1891@subsubsection occt_visu_5_2_2 Provided services
1893The *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:
72b7576f 1894 * Default parameters of the viewer,
1895 * Views (orthographic, perspective),
1896 * Lighting (positional, directional, ambient, spot, headlight),
bf62b306 1897 * Clipping planes (note that only Z-clipping planes can work with the Phigs interface),
1898 * Instantiated sequences of views, planes, light sources, graphic structures, and picks,
72b7576f 1899 * Various package methods.
bf62b306 1901@subsubsection occt_visu_5_2_3 A programming example
72b7576f 1902
bf62b306 1903This sample TEST program for the *V3d* Package uses primary packages *Xw* and *Graphic3d* and secondary packages *Visual3d, Aspect, Quantity, Phigs* and *math*.
72b7576f 1904
bf62b306 1905~~~~~
1906//Create a default display connection
1907Handle(Aspect_DisplayConnection) aDisplayConnection = new Aspect_DisplayConnection();
72b7576f 1908
bf62b306 1909//Create a Graphic Driver from the default *Aspect_DisplayConnection*
1910Handle(Graphic3d_GraphicDriver) GD = Graphic3d::InitGraphicDriver (aDisplayConnection);
1912//Create a Viewer to this Driver
1913Handle(V3d_Viewer) VM = new V3d_Viewer(GD, 400.,
1914// Space size
1915V3d_Xpos,// Default projection Quantity_NOC_DARKVIOLET,
1916// Default background
72b7576f 1917V3d_ZBUFFER,
bf62b306 1918// Type of visualization
72b7576f 1919V3d_GOURAUD,
bf62b306 1920// Shading model
72b7576f 1921V3d_WAIT);
bf62b306 1922// Update mode
1923*// Create a structure in this Viewer *
1924Handle(Graphic3d_Structure) S =
1925new Graphic3d_Structure(VM-Viewer()) ;
72b7576f 1926
bf62b306 1927*// Type of structure *
1928S-SetVisual (Graphic3d_TOS_SHADING);
72b7576f 1929
bf62b306 1930*// Create a group of primitives in this structure*
1931Handle(Graphic3d_Group) G = new Graphic3d_Group(S) ;
72b7576f 1932
bf62b306 1933*// Fill this group with one polygon of size 100*
1934Graphic3d_Array1OfVertex Points(0,3) ;
1935Points(0).SetCoord(-100./2.,-100./2.,-100./2.) ;
1936Points(1).SetCoord(-100./2., 100./2.,-100./2.) ;
1937Points(2).SetCoord( 100./2., 100./2.,-100./2.) ;
1938Points(3).SetCoord( 100./2.,-100./2.,-100./2.) ; Normal.SetCoord(0.,0.,1.) ;
1939G-Polygon(Points,Normal) ;
72b7576f 1940
bf62b306 1941*// Create Ambient and Infinite Lights in this Viewer*
1942Handle(V3d_AmbientLight) L1 = new V3d_AmbientLight
1943(VM,Quantity_NOC_GRAY50) ;
1944Handle(V3d_DirectionalLight) L2 = new V3d_DirectionalLight
1945(VM,V3d_XnegYnegZneg,Quantity_NOC_WHITE) ;
72b7576f 1946
bf62b306 1947*// Create a 3D quality Window with the same DisplayConnection*
1948Handle(Xw_Window) W =
1949new Xw_Window(aDisplayConnection,"Test V3d",0.5,0.5,0.5,0.5) ;
72b7576f 1950
bf62b306 1951*// Map this Window to this screen*
1952 W-Map() ;
72b7576f 1953
bf62b306 1954*// Create a Perspective View in this Viewer*
1955Handle(V3d_PerspectiveView) V =
1956new V3d_PerspectiveView(VM);
72b7576f 1957
bf62b306 1958*// Set the Eye position*
1959V-SetEye(100.,100.,100.) ;
72b7576f 1960
bf62b306 1961*// Associate this View with the Window *
1962V-SetWindow(W) ;
72b7576f 1963
bf62b306 1964*// Activate ALL defined Lights in this View *
1965V-SetLightOn() ;
72b7576f 1966
bf62b306 1967*// Display ALL structures in this View *
1968(VM-Viewer())-Display() ;
72b7576f 1969
bf62b306 1970*// Finally update the Visualization in this View *
1971V-Update() ;
72b7576f 1973
bf62b306 1974@subsubsection occt_visu_5_2_4 Glossary of view transformations
72b7576f 1975
bf62b306 1976The following terms are used to define view orientation, i.e. transformation from World Coordinates (WC) to the View Reference Coordinates system (VRC):
1977* **View Reference Point (VRP)** - defines the origin of View Reference Coordinates.
1978* **View Reference Plane Normal (VPN)** - defines the normal of projection plane of the view.
1979* **View Reference Up Vector (VUP)** - defines the vertical of observer of the view.
72b7576f 1980
bf62b306 1981The following terms are used to define view mapping, i.e. transformation from View Reference Coordinates (VRC) to the Normalized Projection Coordinates (NPC):
1982* **Projection type** - Orthographic or perspective.
1983* **Projection Reference Point (PRP)** - Defines the observer position.
1984* **Front Plane Distance (FPD)** - Defines the position of the front clipping plane in View Reference Coordinates system.
1985* **Back Plane Distance (BPD)** Defines the position of the back clipping plane in View Reference Coordinates system.
1986* **View Plane Distance (VPD)** Defines the position of the view projection plane in View Reference Coordinates system. View plane must be located between front and back clipping planes.
1987* **Window Limits** Defines the visible part of the view projection plane (left, right, top and bottom boundaries: *Umin, Umax, Vmax* and *Vmin* respectively) in View Reference Coordinates.
72b7576f 1988
bf62b306 1989The *V3d_View* API uses the following terms to define view orientation and mapping:
1990* **At** - Position of View Reference Point (VRP) in World Coordinates
1991* **Eye** - Position of the observer (projection reference point) in World Coordinates. Influences to the view projection vector and depth value.
1992* **Proj** - View projection vector (VPN)
1993* **Up** - Position of the high point / view up vector (VUP)
1994* **Depth** - Distance between Eye and At point
1995* **ZSize** - Distance between front and back clipping planes
1996* **Size** - Window size in View Reference Coordinates
1997* **Focal Reference point** - Position of Projection Reference Point (PRP) in World Coordinates
1998* **Focale** - Distance between Projection Reference Point (PRP) and View projection plane
72b7576f 1999
72b7576f 2000
bf62b306 2001@subsubsection occt_visu_5_2_5 Management of perspective projection
dba69de2 2002
bf62b306 2003The perspective projection allows definition of viewing volume as a truncated pyramid (frustum) with apex at the Projection Reference Point. In the View Reference Coordinate system it can be presented by the following picture:
72b7576f 2004
bf62b306 2005@image html visualization_image023.png "View Reference Coordinate System, perspective viewing volume and view mapping parameter"
2006@image latex visualization_image023.png "View Reference Coordinate System, perspective viewing volume and view mapping parameter"
2008During panning, window limits are changed, as if a sort of "frame" through which the user sees a portion of the view plane was moved over the view. The perspective frustum itself remains unchanged.
72b7576f 2009
2010The perspective projection is defined by two parameters:
bf62b306 2011 * *Depth* value defines distance between Projection Reference Point and the nearest (front) clipping plane.
2012 * *ZSize* defines distance between Front and Back clipping planes. The influence of this parameter is caused by the OCCT specific to center viewing volume around View Reference Point so the front and back plane distances were the same: *FPD = BPD = ZSize / 2*.
2014**Note** that the closer the displayed object to the Projection Reference Point the more visible its perspective distortion. Thus, in order to get a good perspective it is recommended to set **ZSize** value comparable with the expected model size and small Depth value.
72b7576f 2015
bf62b306 2016However, very small Depth values might lead to inaccuracy of "fit all" operation and to non-realistic perspective distortion.
72b7576f 2017
bf62b306 2018Let us see the example:
2020// Create a Perspective View in Viewer VM
2021Handle(V3d_PerspectiveView) V = new V3d_PerspectiveView(VM);
72b7576f 2022
bf62b306 2023// Set the ZSize
2024V-SetZSize(2000.) ;
72b7576f 2025
bf62b306 2026// Set the Depth value
2027V-SetDepth(20.) ;
72b7576f 2028
bf62b306 2029// Set the current mapping as default to be used by Reset() operation
2030V-SetViewMappingDefault() ;
72b7576f 2032
bf62b306 2033As an alternative to manual setting of perspective parameters the *V3d_View::DepthFitAll* function can be used.
72b7576f 2034
bf62b306 2035~~~~~
2036// Display  shape in Viewer VM
2037Handle(AIS_InteractiveContext) aContext = new AIS_InteractiveContext(VM);
72b7576f 2038aContext-Display(shape);
bf62b306 2040// Create a Perspective View in Viewer VM
2041Handle(V3d_PerspectiveView) V = new V3d_PerspectiveView(VM);
72b7576f 2042
bf62b306 2043// Set automatically the perspective parameters
2044V-DepthFitAll() ;
72b7576f 2045
bf62b306 2046// Fit view to object size
72b7576f 2047V-FitAll();
bf62b306 2049// Set the current mapping as default to be used by Reset() operation
2050V-SetViewMappingDefault() ;
72b7576f 2052
bf62b306 2053It is necessary to take into account that during rotation Z size of the view might be modified automatically to fit the model into the viewing volume.
72b7576f 2054
bf62b306 2055Make sure the Eye point never gets between the Front and Back clipping planes.
72b7576f 2056
bf62b306 2057In perspective view, changing Z size results in changed perspective effect. To avoid this, an application should specify the maximum expected Z size using *V3d_View::SetZSize()* method in advance.
72b7576f 2058
bf62b306 2059*V3d_View::FitAll()* with *FitZ = Standard_True* and *V3d_View::ZFitAll()* also change the perspective effect and should therefore be used with precautions similar to those for rotation.
72b7576f 2060
bf62b306 2061@subsubsection occt_visu_5_2_6 Underlay and overlay layers management
72b7576f 2062
bf62b306 2063In addition to interactive 3d graphics displayed in the view you can display an underlying and overlying graphics: text, color scales, drawings.
72b7576f 2064
bf62b306 2065All *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.
72b7576f 2066
bf62b306 2067The method *V3d_View::SetLayerMgr(const Handle (V3d_LayerMgr)& aMgr)* allows assigning a custom layer manager to the *V3d* view.
72b7576f 2068
bf62b306 2069There are three virtual methods to prepare graphics in the manager for further drawing (set up layer dimensions, draw static graphics). These methods can be redefined:
2071 void V3d_LayerMgr::Begin ()
2072 void V3d_LayerMgr::Redraw ()
2073 void V3d_LayerMgr::End ()
72b7576f 2075
bf62b306 2076The layer manager controls layers (*Visual3d_Layer*) and layer items (*Visual3d_LayerItem*). Both the overlay and underlay layers can be created by the layer manager.
72b7576f 2077
bf62b306 2078The layer entity is presented by the *Visual3d_Layer* class. This entity provides drawing services in the layer, for example:
2080 void Visual3d_Layer::DrawText
2081 void Visual3d_Layer::DrawRectangle
2082 void Visual3d_Layer::SetColor
2083 void Visual3d_Layer::SetViewport
2085The following example demonstrates how to draw overlay graphics by the *V3d_LayerMgr*:
72b7576f 2086
bf62b306 2087~~~~~
2088// redefined method of V3d_LayerMgr
2089void MyLayerMgr::Redraw ()
72b7576f 2090{
bf62b306 2091  Quantity_Color aRed (Quantity_NOC_RED);
2092  myOverlayLayer-SetColor (aRed);
2093  myOverlayLayer-DrawRectangle (0, 0, 100, 100);
72b7576f 2094}
bf62b306 2095~~~~~
72b7576f 2096
bf62b306 2097The 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:
72b7576f 2098
bf62b306 2099~~~~~
2100 void Visual3d_Layer::AddLayerItem (const Handle (Visual3d_LayerItem)& Item)
2101 void Visual3d_Layer::RemoveLayerItem (const Handle (Visual3d_LayerItem)& Item) 
2102 void Visual3d_Layer::RemoveAllLayerItems ()
2103 const Visual3d_NListOfLayerItem& Visual3d_Layer::GetLayerItemList ()  
2105The layer’s items are rendered when the method *void Visual3d_Layer::RenderLayerItems()* is called by the graphical driver.
72b7576f 2106
bf62b306 2107The *Visual3d_LayerItem* has virtual methods that are used to render the item:
2109 void Visual3d_LayerItem::RedrawLayerPrs ()
2110 void Visual3d_LayerItem::ComputeLayerPrs ()
72b7576f 2112
bf62b306 2113The 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:
2115 void Visual3d_LayerItem::SetNeedToRecompute (const Standard_Boolean NeedToRecompute)
2116 Standard_Boolean Visual3d_LayerItem::IsNeedToRecompute
72b7576f 2118
bf62b306 2119An example of *Visual3d_LayerItem* is *V3d_ColorScaleLayerItem* that represents the color scale entity as the layer’s item.
2120The *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:
72b7576f 2121
72b7576f 2122<h4>Example </h4>
bf62b306 2124~~~~~
2125// tell V3d_ColorScale to draw itself
2126void V3d_ColorScaleLayerItem::RedrawLayerPrs ()
72b7576f 2127{
bf62b306 2128  Visual3d_LayerItem::RedrawLayerPrs ()
2129  if (!MyColorScale.IsNull ())
2130    MyColorScale-DrawScale ();
72b7576f 2131}
bf62b306 2133// V3d_ColorScale has a reference to a LayerMgr
2134void V3d_ColorScale::DrawScale ()
2136    // calls *V3d_ColorScale::PaintRect, V3d_ColorScale::PaintText, etc …
72b7576f 2138
bf62b306 2139// PaintRect method uses overlay layer of LayerMgr to draw a rectangle
2140void V3d_ColorScale::PaintRect
2141       (const Standard_Integer X, const Standard_Integer Y,
2142        const Standard_Integer W, const Standard_Integer H,
2143        const Quantity_Color aColor,
2144        const Standard_Boolean aFilled)
2146  const Handle (Visual3d_Layer)& theLayer =
2147                                 myLayerMgr-Overlay ();
2148    …
2149  theLayer-SetColor (aColor);
2150  theLayer-DrawRectangle (X, Y, W, H);
2151   …
72b7576f 2154
bf62b306 2155@subsubsection occt_visu_5_2_7 View background styles
2156There are three types of background styles available for *V3d_view*: solid color, gradient color and image.
72b7576f 2157
bf62b306 2158To set solid color for the background you can use the following methods:
2160 void V3d_View::SetBackgroundColor
2161 (const Quantity_TypeOfColor Type,
2162  const Quantity_Parameter V1,
2163  const Quantity_Parameter V2,
2164  const Quantity_Parameter V3)
72b7576f 2166
bf62b306 2167This 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*.
72b7576f 2168
bf62b306 2169**Note** that the color value parameters *V1,V2,V3* should be in the range between *0.0-1.0.*
72b7576f 2170
bf62b306 2171~~~~~
2172 void V3d_View::SetBackgroundColor(const Quantity_Color &Color)
2173 void V3d_View::SetBackgroundColor(const Quantity_NameOfColor Name)
72b7576f 2175
bf62b306 2176The gradient background style could be set up with the following methods:
2178 void V3d_View::SetBgGradientColors
2179 (const Quantity_Color& Color1,
2180  const Quantity_Color& Color2,
2181  const Aspect_GradientFillMethod FillStyle,
2182  const Standard_Boolean update)
2184 void V3d_View::SetBgGradientColors
2185 (const Quantity_NameOfColor Color1,
2186  const Quantity_NameOfColor Color2,
2187  const Aspect_GradientFillMethod FillStyle,
2188  const Standard_Boolean update)
72b7576f 2190
bf62b306 2191The *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.
72b7576f 2192
bf62b306 2193The fill style can be also set with the method *void V3d_View::SetBgGradientStyle(const Aspect_GradientFillMethod AMethod, const Standard_Boolean update)*.
72b7576f 2194
bf62b306 2195To get the current background color you can use the following methods:
2197 void V3d_View::BackgroundColor
2198 (const Quantity_TypeOfColor Type,
2199  Quantity_Parameter &V1,
2200  Quantity_Parameter &V2,
2201  Quantity_Parameter &V3)
2202 Quantity_Color V3d_View::BackgroundColor()
2203 void V3d_View::GradientBackgroundColors(Quantity_Color& Color1, Quantity_Color& Color2)
2204 Aspect_GradientBackground GradientBackground()
2207To set the image as a background and change the background image style you can use the following methods:
2209 * void V3d_View::SetBackgroundImage
2210 (const Standard_CString FileName,
2211  const Aspect_FillMethod FillStyle,
2212  const Standard_Boolean update)
2213 * void V3d_View::SetBgImageStyle
2214 (const Aspect_FillMethod FillStyle,
2215  const Standard_Boolean update)
72b7576f 2217
bf62b306 2218The *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:
2219 * *Aspect_FM_NONE* -  draws the image in the default position;
2220 * *Aspect_FM_CENTERED* - draws the image at the center of the view;
2221 * *Aspect_FM_TILED* tiles the view with the image;
2222 * *Aspect_FM_STRETCH* stretches the image over the view.
72b7576f 2223
bf62b306 2224@subsubsection occt_visu_5_2_8 User-defined clipping planes
2225The ability to define custom clipping planes could be very useful for some tasks. The *V3d* view provides such an opportunity.
72b7576f 2226
bf62b306 2227The *V3d_Plane* class provides the services of 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:
2229 void V3d_Plane::SetPlane
2230 (const Quantity_Parameter A,
2231  const Quantity_Parameter B,
2232  const Quantity_Parameter C,
2233  const Quantity_Parameter D)
2234 void V3d_Plane::Plane
2235 (Quantity_Parameter& A,
2236  Quantity_Parameter& B,
2237  Quantity_Parameter& C,
2238  Quantity_Parameter& D)
2240 *V3d_Plane* also provides display services:
2242 * void V3d_Plane::Display
2243 (const Handle(V3d_View)& aView,
2244  const Quantity_Color& aColor)
2245 * void V3d_Plane::Erase ()
2246 * Standard_Boolean V3d_Plane::IsDisplayed ()
2248The *Display* method could be redefined to provide custom representation of the clipping plane.
72b7576f 2249
bf62b306 2250The clipping planes could be activated with the methods *void V3d_View::SetPlaneOn (const Handle(V3d_Plane)& MyPlane)* and *void V3d_View::SetPlaneOn()*
72b7576f 2251
bf62b306 2252The first method appends the given *V3d_Plane* to the internal list of user-defined clipping planes of a view and activates it. If the plane is already in the list, it becomes activated. The second method activates all of the planes defined for the view.
72b7576f 2253
bf62b306 2254The clipping planes could be deactivated with the similar methods *void V3d_View::SetPlaneOff(const Handle(V3d_Plane)& MyPlane)* and *void V3d_View::SetPlaneOff()*
72b7576f 2255
bf62b306 2256The only difference is that these methods remove the user-defined clipping planes from the internal list. Thus, the view retains only active clipping planes.
72b7576f 2257
bf62b306 2258You can iterate through the active planes using the following methods:
2259 * *void V3d_View::InitActivePlanes()* - sets the iterator to the beginning of the internal list of clipping planes;
2260 * *Standard_Boolean V3d_View::MoreActivePlanes()* returns *Standard_True* if there are more active planes to return;
2261 * *void V3d_View::NextActivePlanes()* sets the iterator to the next active plane in the list;
2262 * *Handle(V3d_Plane) V3d_View::ActivePlane()* returns the active plane
72b7576f 2263
bf62b306 2264or check if a certain clipping plane has been activated with method *Standard_Boolean V3d_View::IsActivePlane (const Handle (V3d_Plane)& aPlane)*
2266The number of clipping planes is limited. The method *Standard_Boolean V3d_View::IfMorePlanes()* allows checking if it is possible to activate at least one more plane in the view or the limit has been reached.
72b7576f 2268<h4>Example </h4>
bf62b306 2270~~~~~
2271// try to use an existing clipping plane or create a new one
2272Handle(V3d_Plane) aCustomPlane;
2273myView-InitActivePlanes ();
2274if (myView-MoreActivePlanes ())
2275  aCustomPlane = myView-ActivePlane ();
2277  aCustomPlane = new V3d_Plane ();
2279// calculate new coefficients
2280Standard_Real a, b, c, d;
2281Standard_Real x = 0.0, y = 0.0, z = 10.0;
2282Standard_Real dx = 0.0, dy = 0.0, dz = 1.0;
2283gp_Pln aPln (gp_Pnt (x, y, z), gp_Dir (dx, dy, dz));
2284aPln.Coefficients (a, b, c, d);
2286// update plane
2287aCustomPlane-SetPlane (a, b, c, d);
2288myView-SetPlaneOn (aCustomPlane);
72b7576f 2290
bf62b306 2291@subsubsection occt_visu_5_2_9 Dumping a 3D scene into an image file
2292The 3D scene displayed in the view could 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).
72b7576f 2293
bf62b306 2294The *V3d_View* has the following methods for dumping the 3D scene:
2295* *Standard_Boolean V3d_View::Dump (const Standard_CString theFile, const Image_TypeOfImage theBufferType)* - dumps the scene into an image file with the view dimensions.
2296* *Standard_Boolean V3d_View::Dump (const Standard_CString theFile, const Aspect_FormatOfSheetPaper theFormat, const Image_TypeOfImage theBufferType)* - allows making the dimensions of the output image compatible to a certain format of printing paper passed by *theFormat* argument.
2298These methods dump the 3D scene into an image file passed by its name and path as theFile.
72b7576f 2299
bf62b306 2300The raster image data handling algorithm is based on the Image_PixMap class. The supported extensions are ".png", ".bmp", ".png", ".png".
72b7576f 2301
bf62b306 2302The value passed as *theBufferType* argument defines the type of the buffer for an output image *(RGB, RGBA, floating-point, RGBF, RGBAF)*. Both methods return *Standard_True* if the scene has been successfully dumped.
72b7576f 2303
bf62b306 2304**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.
72b7576f 2305
bf62b306 2306* Handle_Image_PixMap V3d_View::ToPixMap (const Standard_Integer theWidth, const Standard_Integer theHeight, const Image_TypeOfImage theBufferType, const Standard_Boolean theForceCentered)* allows dumping the displayed 3d scene into a pixmap with a width and height passed as *theWidth* and theHeight arguments.
72b7576f 2307
bf62b306 2308The value passed as *theBufferType* argument defines the type of the buffer for a pixmap *(RGB, RGBA, floating-point, RGBF, RGBAF)*. The last parameter allows centering the 3D scene on dumping.
72b7576f 2309
bf62b306 2310All 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:
2311* Create display connection;
2312* Initialize graphic driver;
2313* Create a window;
2314* Set up the window as virtual, *Aspect_Window::SetVirtual()* ;
2315* Create a view and an interactive context;
2316* Assign the virtual window to the view;
2317* Display a 3D scene;
2318* Use one of the functions described above to dump the 3D scene.
72b7576f 2319
bf62b306 2320The following example demonstrates this procedure for *WNT_Window* :
72b7576f 2321
bf62b306 2322~~~~~
2323// create a dummy display connection
2324Handle(Aspect_DisplayConnection) aDisplayConnection;
2326// create a graphic driver
2327Handle (Graphic3d_GraphicDriver) aDriver = Graphic3d::InitGraphicDriver (aDisplayConnection);
2329// create a window
2330Standard_Integer aDefWidth  = 800;
2331Standard_Integer aDefHeight = 600;
2332Handle (WNT_WClass) aWClass =
2333             new WNT_WClass ("Virtual Class",DefWindowProc,
2334                             CS_VREDRAW | CS_HREDRAW, 0, 0,
2335                             ::LoadCursor (NULL, IDC_ARROW));
2336Handle (WNT_Window) aWindow =
2337             new WNT_Window ("VirtualWnd",  aWClass,
2338                             WS_OVERLAPPEDWINDOW, 0, 0,
2339                             aDefWidth, aDefHeight);
2341// set up the window as virtual
2342aWindow-SetVirtual (Standard_True);
2344// create a view and an interactive context
2345Handle (V3d_Viewer) aViewer =
2346             new V3d_Viewer (aDriver,
2347                             Standard_ExtString ("Virtual"));
2348Handle (AIS_InteractiveContext) aContext =
2349             new AIS_InteractiveContext (aViewer);
2350Handle (V3d_View) aView = aViewer-CreateView ();
2352// assign the virtual window to the view
2353aView-SetWindow (aWindow);
2355// display a 3D scene
2356Handle (AIS_Shape) aBox =
2357             new AIS_Shape (BRepPrimAPI_MakeBox (5, 5, 5));
2358aContext-Display (aBox);
72b7576f 2360
bf62b306 2361// dump the 3D scene into an image file
2362aView-Dump ("3dscene.png");
72b7576f 2364
bf62b306 2365@subsubsection occt_visu_5_2_10 Printing a 3D scene
72b7576f 2366
bf62b306 2367The 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.
72b7576f 2368
bf62b306 2369The 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:
72b7576f 2370
bf62b306 2371*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.
72b7576f 2372
bf62b306 2373You can define the filename for the printer driver if you want to print out the result into a file.
2374If you do not want to print the background, you can pass *Standard_False* as the *showBackground* argument.
2375The *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*
72b7576f 2376
bf62b306 2377The 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.
72b7576f 2378
bf62b306 2379**Note** that at the moment printing is implemented only for Windows.
72b7576f 2380
bf62b306 2381@subsubsection occt_visu_5_2_11 Vector image export
72b7576f 2382
bf62b306 2383The 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 your 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).
72b7576f 2384
bf62b306 2385The 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:
72b7576f 2386
bf62b306 2387The *FileName* defines the output image file name and the *Format* argument defines the output file format:
2388 * Graphic3d_EF_PostScript (PS),
2389 * Graphic3d_EF_EhnPostScript (EPS),
2390 * Graphic3d_EF_TEX (TEX),
2391 * Graphic3d_EF_PDF (PDF),
2392 * Graphic3d_EF_SVG (SVG),
2393 * Graphic3d_EF_PGF (PGF)
72b7576f 2394
bf62b306 2395The *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.
72b7576f 2396
bf62b306 2397The *Export* method supports only basic 3d graphics and has several limitations:
2398 * Rendering large scenes could be slow and can lead to large output files;
2399 * Transparency is only supported for PDF and SVG output;
2400 * Textures and some effects are not supported by the GL2PS library.
72b7576f 2401
bf62b306 2402@section occt_visu_6 Graphic Attributes
72b7576f 2403
bf62b306 2404@subsection occt_visu_6_1 Aspect Package
72b7576f 2405
bf62b306 2406The *Aspect* package provides classes for the graphic elements in the viewer:
2407 * Color maps,
2408 * Pixels,
2409 * Groups of graphic attributes,
2410 * Edges, lines, background,
2411 * Font classes,
2412 * Width map classes,
2413 * Marker map classes,
2414 * Type of Line map classes,
2415 * Window,
2416 * Driver, PlotterDriver (inherited by PS_Driver), WindowDriver,
2417 * Enumerations for many of the above,
2418 * Array instantiations for edges,
2419 * Array instantiations for map entries for color, type, font, width, and marker.
72b7576f 2420
72b7576f 2421