0031456: Visualization - move out Dimensions and Relations from package AIS to PrsDims
[occt.git] / dox / user_guides / visualization / visualization.md
ba06f8bb 1Visualization {#occt_user_guides__visualization}
bf62b306 2========================
72b7576f 4
bf62b306 5@section occt_visu_1 Introduction
72b7576f 6
7c42f3f4 7Visualization in Open CASCADE Technology is based on the separation of:
8 * on the one hand -- the data which stores the geometry and topology of the entities you want to display and select, and
9 * on the other hand -- its **presentation** (what you see when an object is displayed in a scene) and **selection** (possibility to choose the whole object or its sub-parts interactively to apply application-defined operations to the selected entities).
72b7576f 10
18006a0f 11Presentations are managed through the **Presentation** component, and selection through the **Selection** component.
72b7576f 12
7c42f3f4 13**Application Interactive Services** (AIS) provides the means to create links between an application GUI viewer and the packages, which are used to manage selection and presentation, which makes management of these functionalities in 3D more intuitive and consequently, more transparent.
72b7576f 14
7c42f3f4 15*AIS* uses the notion of the *Interactive Object*, a displayable and selectable entity, which represents an element from the application data. As a result, in 3D, you, the user, have no need to be familiar with any functions underlying AIS unless you want to create your own interactive objects or selection filters.
72b7576f 16
7c42f3f4 17If, 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.
72b7576f 18
2683e647 19The the following packages are used to display 3D objects:
7c42f3f4 20 * *AIS*;
21 * *StdPrs*;
22 * *Prs3d*;
23 * *PrsMgr*;
24 * *V3d*;
4ee1bdf4 25 * *Graphic3d*.
72b7576f 26
18006a0f 27The packages used to display 3D objects are also applicable for visualization of 2D objects.
72b7576f 28
7c42f3f4 29The 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.
72b7576f 30
d6b4d3d0 31@figure{visualization_image003.png,"Key concepts and packages in visualization",400}
72b7576f 32
2683e647 33To answer different needs of CASCADE users, this User's Guide offers the following three paths in reading it.
7c42f3f4 34
35 * If the 3D services proposed in AIS meet your requirements, you need only read chapter 3 @ref occt_visu_3 "AIS: Application Interactive Services".
36 * If you need more detail, for example, a selection filter on another type of entity -- you should read chapter 2 @ref occt_visu_2 "Fundamental Concepts", chapter 3 @ref occt_visu_3 "AIS: Application Interactive Services", and 4 @ref occt_visu_4 "3D Presentations". You may want to begin with the chapter presenting AIS.
7863dabb 38For advanced information on visualization algorithms, see our <a href="https://www.opencascade.com/content/tutorial-learning">E-learning & Training</a> offerings.
72b7576f 39
7c42f3f4 40@section occt_visu_2 Fundamental Concepts
72b7576f 41
7c42f3f4 42@subsection occt_visu_2_1 Presentation
72b7576f 43
7c42f3f4 44In 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.
72b7576f 45
7c42f3f4 46@subsubsection occt_visu_2_1_1 Structure of the Presentation
72b7576f 47
2683e647 48Displaying an object on the screen involves three kinds of entities:
bf62b306 49 * a presentable object, the *AIS_InteractiveObject*
7c42f3f4 50 * a viewer
51 * an interactive context, the *AIS_InteractiveContext*.
53#### The presentable object
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.
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.
72b7576f 58
7c42f3f4 59Each object to be presented individually must be presentable or associated with a presentable object.
72b7576f 60
7c42f3f4 61#### The viewer
72b7576f 62
7c42f3f4 63The 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.
72b7576f 64
7c42f3f4 65#### The Interactive Context
72b7576f 66
7c42f3f4 67The 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.
72b7576f 68
bf62b306 69@subsubsection occt_visu_2_1_2 Presentation packages
72b7576f 70
7c42f3f4 71Presentation 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.
18006a0f 72
7c42f3f4 73* *AIS* package provides all classes to implement interactive objects (presentable and selectable entities).
74* *PrsMgr* package provides low level services and is only to be used when you do not want to use the services provided by AIS. It contains all classes needed to implement the presentation process: abstract classes *Presentation* and *PresentableObject* and concrete class *PresentationManager3d*.
75* *StdPrs* package provides ready-to-use standard presentation algorithms for specific geometries: points, curves and shapes of the geometry and topology toolkits.
18006a0f 76* *Prs3d* package provides generic presentation algorithms such as wireframe, shading and hidden line removal associated with a *Drawer* class, which controls the attributes of the presentation to be created in terms of color, line type, thickness, etc.
7c42f3f4 77* *V3d* package provides the services supported by the 3D viewer.
2683e647 78* *Graphic3d* package provides resources to create 3D graphic structures.
18006a0f 79* *Visual3d* package contains classes implementing commands for 3D viewer.
80* *DsgPrs* package provides tools for display of dimensions, relations and XYZ trihedrons.
72b7576f 81
7c42f3f4 82@subsubsection occt_visu_2_1_3 A Basic Example: How to display a 3D object
72b7576f 83
bf62b306 84~~~~~
7c42f3f4 85Handle(V3d_Viewer) theViewer;
86Handle(AIS_InteractiveContext) aContext = new AIS_InteractiveContext (theViewer);
bf62b306 87
7c42f3f4 88BRepPrimAPI_MakeWedge aWedgeMaker (theWedgeDX, theWedgeDY, theWedgeDZ, theWedgeLtx);
89TopoDS_Solid aShape = aWedgeMaker.Solid();
90Handle(AIS_Shape) aShapePrs = new AIS_Shape (aShape); // creation of the presentable object
7863dabb 91aContext->Display (aShapePrs, AIS_Shaded, 0, true); // display the presentable object and redraw 3d viewer
bf62b306 92~~~~~
dba69de2 93
7c42f3f4 94The 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.
72b7576f 95
d6b4d3d0 96@figure{visualization_image004.svg,"Processes involved in displaying a presentable shape",400}
72b7576f 97
7c42f3f4 98@subsection occt_visu_2_2 Selection
72b7576f 99
a7d4dd94 100Standard OCCT selection algorithm is represented by 2 parts: dynamic and static. Dynamic selection causes objects to be automatically highlighted as the mouse cursor moves over them. Static selection allows to pick particular object (or objects) for further processing.
72b7576f 101
a7d4dd94 102There are 3 different selection types:
103 - **Point selection** -- allows picking and highlighting a single object (or its part) located under the mouse cursor;
104 - **Rectangle selection** -- allows picking objects or parts located under the rectangle defined by the start and end mouse cursor positions;
105 - **Polyline selection** -- allows picking objects or parts located under a user-defined non-self-intersecting polyline.
72b7576f 106
7c42f3f4 107For OCCT selection algorithm, all selectable objects are represented as a set of sensitive zones, called **sensitive entities**. When the mouse cursor moves in the view, the sensitive entities of each object are analyzed for collision.
72b7576f 108
a7d4dd94 109@subsubsection occt_visu_2_2_1 Terms and notions
72b7576f 110
a7d4dd94 111This section introduces basic terms and notions used throughout the algorithm description.
72b7576f 112
7c42f3f4 113#### Sensitive entity
72b7576f 114
a7d4dd94 115Sensitive entities in the same way as entity owners are links between objects and the selection mechanism.
72b7576f 116
a7d4dd94 117The purpose of entities is to define what parts of the object will be selectable in particular. Thus, any object that is meant to be selectable must be split into sensitive entities (one or several). For instance, to apply face selection to an object it is necessary to explode it into faces and use them for creation of a sensitive entity set.
72b7576f 118
d6b4d3d0 119@figure{visualization_image005.png,"Example of a shape divided into sensitive entities",400}
72b7576f 120
a7d4dd94 121Depending on the user's needs, sensitive entities may be atomic (point or edge) or complex. Complex entities contain many sub-elements that can be handled by detection mechanism in a similar way (for example, a polyline stored as a set of line segments or a triangulation).
72b7576f 122
a7d4dd94 123Entities are used as internal units of the selection algorithm and do not contain any topological data, hence they have a link to an upper-level interface that maintains topology-specific methods.
72b7576f 124
7c42f3f4 125#### Entity owner
72b7576f 126
a7d4dd94 127Each sensitive entity stores a reference to its owner, which is a class connecting the entity and the corresponding selectable object. Besides, owners can store any additional information, for example, the topological shape of the sensitive entity, highlight colors and methods, or if the entity is selected or not.
72b7576f 128
7c42f3f4 129#### Selection
72b7576f 130
7c42f3f4 131To simplify the handling of different selection modes of an object, sensitive entities linked to their owners are organized into sets, called **selections**.
a7d4dd94 132Each selection contains entities created for a certain mode along with the sensitivity and update states.
72b7576f 133
7c42f3f4 134#### Selectable object
72b7576f 135
a7d4dd94 136Selectable object stores information about all created selection modes and sensitive entities.
138All successors of a selectable object must implement the method that splits its presentation into sensitive entities according to the given mode. The computed entities are arranged in one selection and added to the list of all selections of this object. No selection will be removed from the list until the object is deleted permanently.
7863dabb 140For all standard OCCT shapes, zero mode is supposed to select the whole object (but it may be redefined easily in the custom object). For example, the standard OCCT selection mechanism and *AIS_Shape* determine the following modes (see AIS_Shape::SelectionMode()):
14deaf42 141 - 0 -- selection of the entire object *(AIS_Shape)*;
7863dabb 142 - 1 -- selection of the vertices (TopAbs_VERTEX);
143 - 2 -- selection of the edges (TopAbs_EDGE);
144 - 3 -- selection of the wires (TopAbs_WIRE);
145 - 4 -- selection of the faces (TopAbs_FACE);
146 - 5 -- selection of the shells (TopAbs_SHELL);
147 - 6 -- selection of the constituent solids (TopAbs_SOLID).
a7d4dd94 148
d6b4d3d0 149@figure{visualization_image006.png,"Hierarchy of references from sensitive entity to selectable object",400}
a7d4dd94 150
d6b4d3d0 151@figure{visualization_image007.png,"The principle of entities organization within the selectable object",400}
a7d4dd94 152
7c42f3f4 153#### Viewer selector
a7d4dd94 154
155For each OCCT viewer there is a **Viewer selector** class instance. It provides a high-level API for the whole selection algorithm and encapsulates the processing of objects and sensitive entities for each mouse pick.
a7d4dd94 156The viewer selector maintains activation and deactivation of selection modes, launches the algorithm, which detects candidate entities to be picked, and stores its results, as well as implements an interface for keeping selection structures up-to-date.
7c42f3f4 158#### Selection manager
a7d4dd94 159
160Selection manager is a high-level API to manipulate selection of all displayed objects. It handles all viewer selectors, activates and deactivates selection modes for the objects in all or particular selectors, manages computation and update of selections for each object. Moreover, it keeps selection structures updated taking into account applied changes.
d6b4d3d0 162@figure{visualization_image008.png,"The relations chain between viewer selector and selection manager",400}
a7d4dd94 163
164@subsubsection occt_visu_2_2_2 Algorithm
166All three types of OCCT selection are implemented as a single concept, based on the search for overlap between frustum and sensitive entity through 3-level BVH tree traversal.
7c42f3f4 168#### Selection Frustum
a7d4dd94 169
170The first step of each run of selection algorithm is to build the selection frustum according to the currently activated selection type.
172For the point or the rectangular selection the base of the frustum is a rectangle built in conformity with the pixel tolerance or the dimensions of a user-defined area, respectively. For the polyline selection, the polygon defined by the constructed line is triangulated and each triangle is used as the base for its own frustum. Thus, this type of selection uses a set of triangular frustums for overlap detection.
174The frustum length is limited by near and far view volume planes and each plane is built parallel to the corresponding view volume plane.
d6b4d3d0 176@figure{visualization_image009.png,"",400}
72b7576f 177
d6b4d3d0 178The image above shows the rectangular frustum: a) after mouse move or click, b) after applying the rectangular selection.
182In the image above triangular frustum is set: a) by a user-defined polyline, b) by triangulation of the polygon based on the given polyline, c) by a triangular frustum based on one of the triangles.
72b7576f 183
7c42f3f4 184#### BVH trees
72b7576f 185
a7d4dd94 186To maintain selection mechanism at the viewer level, a speedup structure composed of 3 BVH trees is used.
72b7576f 187
7c42f3f4 188The first level tree is constructed of axis-aligned bounding boxes of each selectable object. Hence, the root of this tree contains the combination of all selectable boundaries even if they have no currently activated selections. Objects are added during the display of *AIS_InteractiveObject* and will be removed from this tree only when the object is destroyed. The 1st level BVH tree is build on demand simultaneously with the first run of the selection algorithm.
72b7576f 189
a7d4dd94 190The second level BVH tree consists of all sensitive entities of one selectable object. The 2nd level trees are built automatically when the default mode is activated and rebuilt whenever a new selection mode is calculated for the first time.
72b7576f 191
a7d4dd94 192The third level BVH tree is used for complex sensitive entities that contain many elements: for example, triangulations, wires with many segments, point sets, etc. It is built on demand for sensitive entities with under 800K sub-elements.
72b7576f 193
d6b4d3d0 194@figure{visualization_image022.png,"Selection BVH tree hierarchy: from the biggest object-level (first) to the smallest complex entity level (third)",400}
72b7576f 195
7c42f3f4 196#### Stages of the algorithm
72b7576f 197
a7d4dd94 198The algorithm includes pre-processing and three main stages.
72b7576f 199
7c42f3f4 200##### Pre-processing
202Implies calculation of the selection frustum and its main characteristics.
72b7576f 203
7c42f3f4 204##### First stage -- traverse of the first level BVH tree
72b7576f 205
7c42f3f4 206After successful building of the selection frustum, the algorithm starts traversal of the object-level BVH tree. The nodes containing axis-aligned bounding boxes are tested for overlap with the selection frustum following the terms of *separating axis theorem (SAT)*. When the traversal goes down to the leaf node, it means that a candidate object with possibly overlapping sensitive entities has been found. If no such objects have been detected, the algorithm stops and it is assumed that no object needs to be selected. Otherwise it passes to the next stage to process the entities of the found selectable object.
208##### Second stage -- traversal of the second level BVH tree
72b7576f 209
a7d4dd94 210At this stage it is necessary to determine if there are candidates among all sensitive entities of one object.
72b7576f 211
a7d4dd94 212First of all, at this stage the algorithm checks if there is any transformation applied for the current object. If it has its own location, then the correspondingly transformed frustum will be used for further calculations. At the next step the nodes of the second level BVH tree of the given object are visited to search for overlapping leaves. If no such leafs have been found, the algorithm returns to the second stage. Otherwise it starts processing the found entities by performing the following checks:
213 - activation check - the entity may be inactive at the moment as it belongs to deactivated selection;
214 - tolerance check - current selection frustum may be too large for further checks as it is always built with the maximum tolerance among all activated entities. Thus, at this step the frustum may be scaled.
72b7576f 215
a7d4dd94 216After these checks the algorithm passes to the last stage.
72b7576f 217
7c42f3f4 218##### Third stage -- overlap or inclusion test of a particular sensitive entity
18006a0f 219
a7d4dd94 220If the entity is atomic, a simple SAT test is performed. In case of a complex entity, the third level BVH tree is traversed. The quantitative characteristics (like depth, distance to the center of geometry) of matched sensitive entities is analyzed and clipping planes are applied (if they have been set). The result of detection is stored and the algorithm returns to the second stage.
72b7576f 221
a7d4dd94 222@subsubsection occt_visu_2_2_3 Packages and classes
72b7576f 223
7c42f3f4 224Selection is implemented as a combination of various algorithms divided among several packages -- *SelectBasics*, *Select3D*, *SelectMgr* and *StdSelect*.
18006a0f 225
7c42f3f4 226#### SelectBasics
18006a0f 227
7c42f3f4 228*SelectBasics* package contains basic classes and interfaces for selection. The most notable are:
7c42f3f4 229 - *SelectBasics_PickResult* -- the structure for storing quantitative results of detection procedure, for example, depth and distance to the center of geometry;
230 - *SelectBasics_SelectingVolumeManager* -- the interface for interaction with the current selection frustum.
18006a0f 231
7c42f3f4 232Each custom sensitive entity must inherit at least *SelectBasics_SensitiveEntity*.
18006a0f 233
7c42f3f4 234#### Select3D
18006a0f 235
7c42f3f4 236*Select3D* package provides a definition of standard sensitive entities, such as:
a7d4dd94 237 - box;
238 - circle;
239 - curve;
240 - face;
241 - group;
242 - point;
243 - segment;
244 - triangle;
245 - triangulation;
246 - wire.
18006a0f 247
0ef04197 248Each basic sensitive entity inherits *Select3D_SensitiveEntity*.
7c42f3f4 249The package also contains two auxiliary classes, *Select3D_SensitivePoly* and *Select3D_SensitiveSet*.
18006a0f 250
0ef04197 251*Select3D_SensitiveEntity* -- the base definition of a sensitive entity.
7c42f3f4 253*Select3D_SensitiveSet* -- a base class for all complex sensitive entities that require the third level BVH usage. It implements traverse of the tree and defines an interface for the methods that check sub-entities.
72b7576f 254
7c42f3f4 255*Select3D_SensitivePoly* -- describes an arbitrary point set and implements basic functions for selection. It is important to know that this class does not perform any internal data checks. Hence, custom implementations of sensitive entity inherited from *Select3D_SensitivePoly* must satisfy the terms of Separating Axis Theorem to use standard OCCT overlap detection methods.
18006a0f 256
7c42f3f4 257#### SelectMgr
18006a0f 258
7c42f3f4 259*SelectMgr* package is used to maintain the whole selection process. For this purpose, the package provides the following services:
a7d4dd94 260 - activation and deactivation of selection modes for all selectable objects;
261 - interfaces to compute selection mode of the object;
262 - definition of selection filter classes;
263 - keeping selection BVH data up-to-date.
18006a0f 264
a7d4dd94 265A brief description of the main classes:
7863dabb 266 - *SelectMgr_BaseFrustum*, *SelectMgr_Frustum*, *SelectMgr_RectangularFrustum*, *SelectMgr_TriangularFrustum* and *SelectMgr_TriangularFrustumSet* -- interfaces and implementations of selecting frustums, these classes implement different SAT tests for overlap and inclusion detection. They also contain methods to measure characteristics of detected entities (depth, distance to center of geometry);
7c42f3f4 267 - *SelectMgr_SensitiveEntity*, *SelectMgr_Selection* and *SelectMgr_SensitiveEntitySet* -- store and handle sensitive entities; *SelectMgr_SensitiveEntitySet* implements a primitive set for the second level BVH tree;
268 - *SelectMgr_SelectableObject* and *SelectMgr_SelectableObjectSet* -- describe selectable objects. They also manage storage, calculation and removal of selections. *SelectMgr_SelectableObjectSet* implements a primitive set for the first level BVH tree;
269 - *SelectMgr_ViewerSelector* -- encapsulates all logics of the selection algorithm and implements the third level BVH tree traverse;
270 - *SelectMgr_SelectionManager* -- manages activation/deactivation, calculation and update of selections of every selectable object, and keeps BVH data up-to-date.
18006a0f 271
7c42f3f4 272#### StdSelect
a7d4dd94 273
7c42f3f4 274*StdSelect* package contains the implementation of some *SelectMgr* classes and tools for creation of selection structures. For example,
275 - *StdSelect_BRepOwner* -- defines an entity owner with a link to its topological shape and methods for highlighting;
276 - *StdSelect_BRepSelectionTool* -- contains algorithms for splitting standard AIS shapes into sensitive primitives;
7863dabb 277 - *StdSelect_ViewerSelector3d* -- an example of *SelectMgr_ViewerSelector* implementation, which is used in a default OCCT selection mechanism;
7c42f3f4 278 - *StdSelect_FaceFilter*, *StdSelect_EdgeFilter* -- implementation of selection filters.
a7d4dd94 279
280@subsubsection occt_visu_2_2_4 Examples of usage
7c42f3f4 282The first code snippet illustrates the implementation of *SelectMgr_SelectableObject::ComputeSelection()* method in a custom interactive object. The method is used for computation of user-defined selection modes.
a7d4dd94 283Let us assume it is required to make a box selectable in two modes -- the whole shape (mode 0) and each of its edges (mode 1).
a7d4dd94 284To select the whole box, the application can create a sensitive primitive for each face of the interactive object. In this case, all primitives share the same owner -- the box itself.
a7d4dd94 285To select box's edge, the application must create one sensitive primitive per edge. Here all sensitive entities cannot share the owner since different geometric primitives must be highlighted as the result of selection procedure.
18006a0f 286
7c42f3f4 288void InteractiveBox::ComputeSelection (const Handle(SelectMgr_Selection)& theSel,
18006a0f 289 const Standard_Integer theMode)
a7d4dd94 291 switch (theMode)
18006a0f 292 {
7c42f3f4 293 case 0: // creation of face sensitives for selection of the whole box
18006a0f 294 {
7c42f3f4 295 Handle(SelectMgr_EntityOwner) anOwner = new SelectMgr_EntityOwner (this, 5);
296 for (Standard_Integer aFaceIter = 1; aFaceIter <= myNbFaces; ++aFaceIter)
297 {
298 Select3D_TypeOfSensitivity aSensType = myIsInterior;
299 theSel->Add (new Select3D_SensitiveFace (anOwner, myFaces[aFaceIter]->PointArray(), aSensType));
300 }
301 break;
18006a0f 302 }
7c42f3f4 303 case 1: // creation of edge sensitives for selection of box edges only
18006a0f 304 {
7c42f3f4 305 for (Standard_Integer anEdgeIter = 1; anEdgeIter <= 12; ++anEdgeIter)
306 {
307 // 1 owner per edge, where 6 is a priority of the sensitive
308 Handle(MySelection_EdgeOwner) anOwner = new MySelection_EdgeOwner (this, anEdgeIter, 6);
309 theSel->Add (new Select3D_SensitiveSegment (anOwner, myFirstPnt[anEdgeIter]), myLastPnt[anEdgeIter]));
310 }
311 break;
18006a0f 312 }
313 }
18006a0f 315~~~~
7c42f3f4 317The algorithms for creating selection structures store sensitive primitives in *SelectMgr_Selection* instance. Each *SelectMgr_Selection* sequence in the list of selections of the object must correspond to a particular selection mode.
7863dabb 318To describe the decomposition of the object into selectable primitives, a set of ready-made sensitive entities is supplied in *Select3D* package. Custom sensitive primitives can be defined through inheritance from *Select3D_SensitiveEntity*.
7c42f3f4 319To make custom interactive objects selectable or customize selection modes of existing objects, the entity owners must be defined. They must inherit *SelectMgr_EntityOwner* interface.
a7d4dd94 320
7c42f3f4 321Selection structures for any interactive object are created in *SelectMgr_SelectableObject::ComputeSelection()* method.
322The example below shows how computation of different selection modes of the topological shape can be done using standard OCCT mechanisms, implemented in *StdSelect_BRepSelectionTool*.
18006a0f 323
a7d4dd94 325 void MyInteractiveObject::ComputeSelection (const Handle(SelectMgr_Selection)& theSelection,
326 const Standard_Integer theMode)
18006a0f 327 {
328 switch (theMode)
329 {
7c42f3f4 330 case 0: StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_SHAPE); break;
331 case 1: StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_VERTEX); break;
332 case 2: StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_EDGE); break;
333 case 3: StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_WIRE); break;
334 case 4: StdSelect_BRepSelectionTool::Load (theSelection, this, myShape, TopAbs_FACE); break;
18006a0f 335 }
336 }
7c42f3f4 339The *StdSelect_BRepSelectionTool* class provides a high level API for computing sensitive entities of the given type (for example, face, vertex, edge, wire and others) using topological data from the given *TopoDS_Shape*.
18006a0f 340
341The traditional way of highlighting selected entity owners adopted by Open CASCADE Technology assumes that each entity owner highlights itself on its own. This approach has two drawbacks:
7863dabb 343 - each entity owner has to maintain its own *Graphic3d_Structure* object, that results in a considerable memory overhead;
7c42f3f4 344 - drawing selected owners one by one is not efficient from the visualization point of view.
72b7576f 345
a7d4dd94 346Therefore, to overcome these limitations, OCCT has an alternative way to implement the highlighting of a selected presentation. Using this approach, the interactive object itself will be responsible for the highlighting, not the entity owner.
18006a0f 347
7c42f3f4 348On the basis of *SelectMgr_EntityOwner::IsAutoHilight()* return value, *AIS_InteractiveContext* object either uses the traditional way of highlighting (in case if *IsAutoHilight()* returns TRUE) or groups such owners according to their selectable objects and finally calls *SelectMgr_SelectableObject::HilightSelected()* or *SelectMgr_SelectableObject::ClearSelected()*, passing a group of owners as an argument.
18006a0f 349
7c42f3f4 350Hence, an application can derive its own interactive object and redefine virtual methods *HilightSelected()*, *ClearSelected()* and *HilightOwnerWithColor()* from *SelectMgr_SelectableObject*. *SelectMgr_SelectableObject::GetHilightPresentation* and *SelectMgr_SelectableObject::GetSelectPresentation* methods can be used to optimize filling of selection and highlight presentations according to the user's needs.
72b7576f 351
7c42f3f4 352After all the necessary sensitive entities are computed and packed in *SelectMgr_Selection* instance with the corresponding owners in a redefinition of *SelectMgr_SelectableObject::ComputeSelection()* method, it is necessary to register the prepared selection in *SelectMgr_SelectionManager* through the following steps:
353 - if there was no *AIS_InteractiveContext* opened, create an interactive context and display the selectable object in it;
354 - load the selectable object to the selection manager of the interactive context using *AIS_InteractiveContext::Load()* method. If the selection mode passed as a parameter to this method is not equal to -1, *ComputeSelection()* for this selection mode will be called;
355 - activate or deactivate the defined selection mode using *AIS_InteractiveContext::Activate()* or *AIS_InteractiveContext::Deactivate()* methods.
72b7576f 356
7c42f3f4 357After these steps, the selection manager of the created interactive context will contain the given object and its selection entities, and they will be involved in the detection procedure.
72b7576f 358
a7d4dd94 359The code snippet below illustrates the above steps. It also contains the code to start the detection procedure and parse the results of selection.
72b7576f 360
a7d4dd94 361~~~~~
a7d4dd94 362// Suppose there is an instance of class InteractiveBox from the previous sample.
363// It contains an implementation of method InteractiveBox::ComputeSelection() for selection
364// modes 0 (whole box must be selected) and 1 (edge of the box must be selectable)
7c42f3f4 365Handle(InteractiveBox) theBox;
366Handle(AIS_InteractiveContext) theContext;
a7d4dd94 367// To prevent automatic activation of the default selection mode
7c42f3f4 368theContext->SetAutoActivateSelection (false);
369theContext->Display (theBox, false);
a7d4dd94 370
371// Load a box to the selection manager without computation of any selection mode
7c42f3f4 372theContext->Load (theBox, -1, true);
a7d4dd94 373// Activate edge selection
7c42f3f4 374theContext->Activate (theBox, 1);
a7d4dd94 375
7c42f3f4 376// Run the detection mechanism for activated entities in the current mouse coordinates and in the current view.
377// Detected owners will be highlighted with context highlight color
7863dabb 378theContext->MoveTo (aXMousePos, aYMousePos, myView, false);
a7d4dd94 379// Select the detected owners
7c42f3f4 380theContext->Select();
a7d4dd94 381// Iterate through the selected owners
7c42f3f4 382for (theContext->InitSelected(); theContext->MoreSelected() && !aHasSelected; theContext->NextSelected())
a7d4dd94 383{
7c42f3f4 384 Handle(AIS_InteractiveObject) anIO = theContext->SelectedInteractive();
a7d4dd94 385}
72b7576f 386
a7d4dd94 387// deactivate all selection modes for aBox1
7c42f3f4 388theContext->Deactivate (aBox1);
bf62b306 389~~~~~
72b7576f 390
a7d4dd94 391It is also important to know, that there are 2 types of detection implemented for rectangular selection in OCCT:
392 - <b>inclusive</b> detection. In this case the sensitive primitive is considered detected only when all its points are included in the area defined by the selection rectangle;
393 - <b>overlap</b> detection. In this case the sensitive primitive is considered detected when it is partially overlapped by the selection rectangle.
72b7576f 394
a7d4dd94 395The standard OCCT selection mechanism uses inclusion detection by default. To change this, use the following code:
72b7576f 396
a7d4dd94 397~~~~~
7c42f3f4 398// Assume there is a created interactive context
399const Handle(AIS_InteractiveContext) theContext;
a7d4dd94 400// Retrieve the current viewer selector
7c42f3f4 401const Handle(StdSelect_ViewerSelector3d)& aMainSelector = theContext->MainSelector();
a7d4dd94 402// Set the flag to allow overlap detection
7c42f3f4 403aMainSelector->AllowOverlapDetection (true);
a7d4dd94 404~~~~~
72b7576f 405
7c42f3f4 406@section occt_visu_3 Application Interactive Services
407@subsection occt_visu_3_1 Introduction
72b7576f 408
7c42f3f4 409Application Interactive Services allow managing presentations and dynamic selection in a viewer in a simple and transparent manner.
410The central entity for management of visualization and selections is the **Interactive Context**. It is connected to the main viewer.
72b7576f 411
7c42f3f4 412Interactive context by default starts at **Neutral Point** with each selectable object picked as a whole, but the user might activate **Local Selection** for specific objects to make selectable parts of the objects.
413Local/global selection is managed by a list of selection modes activated for each displayed object with 0 (default selection mode) usually meaning Global (entire object) selection.
72b7576f 414
7c42f3f4 415**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.
72b7576f 416
7c42f3f4 417An 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.
418When an Interactive Object is visualized, the required graphic attributes are taken from its own **Drawer** (*Prs3d_Drawer*) if it has the required custom attributes or otherwise from the context drawer.
72b7576f 419
d6b4d3d0 420@figure{visualization_image017.png,"",360}
72b7576f 421
7c42f3f4 422It 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 only within at the Neutral Point, others only within Local Selection. It is possible to program custom filters and load them into the interactive context.
72b7576f 423
bf62b306 424@subsection occt_visu_3_2 Interactive objects
72b7576f 425
18006a0f 426Entities which are visualized and selected in the AIS viewer are objects. They connect the underlying reference geometry of a model to its graphic representation in *AIS*. You can use the predefined OCCT classes of standard interactive objects, for which all necessary functions have already been programmed, or, if you are an advanced user, you can implement your own classes of interactive objects.
bf62b306 428@subsubsection occt_visu_3_2_1 Presentations
72b7576f 429
7c42f3f4 430An interactive object can have as many presentations as its creator wants to give it.
4313D presentations are managed by **Presentation Manager** (*PrsMgr_PresentationManager*). As this is transparent in AIS, the user does not have to worry about it.
72b7576f 432
7c42f3f4 433A presentation is identified by an index (*Display Mode*) and by the reference to the Presentation Manager, which it depends on.
434By convention, the default mode of representation for the Interactive Object has index 0.
72b7576f 435
d6b4d3d0 436@figure{visualization_image018.png,"",360}
72b7576f 437
7c42f3f4 438Calculation 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.
72b7576f 439
7c42f3f4 440If you are creating your own type of interactive object, you must implement the Compute function in one of the following ways:
72b7576f 441
bf62b306 442#### For 3D:
72b7576f 443
bf62b306 444~~~~~
7c42f3f4 445void PackageName_ClassName::Compute (const Handle(PrsMgr_PresentationManager3d)& thePresentationManager,
446 const Handle(Prs3d_Presentation)& thePresentation,
447 const Standard_Integer theMode);
bf62b306 448~~~~~
72b7576f 449
7c42f3f4 450#### For hidden line removal (HLR) mode in 3D:
7863dabb 451
bf62b306 452~~~~~
7c42f3f4 453void PackageName_ClassName::Compute (const Handle(Prs3d_Projector)& theProjector,
454 const Handle(Prs3d_Presentation)& thePresentation);
bf62b306 455~~~~~
72b7576f 456
bf62b306 457@subsubsection occt_visu_3_2_2 Hidden Line Removal
72b7576f 458
7c42f3f4 459The 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.
72b7576f 460
7c42f3f4 461By convention, the Interactive Object accepts or rejects the representation of HLR mode. It is possible to make this declaration in one of two ways:
72b7576f 462
7863dabb 463* Initially by using one of the values of the enumeration *PrsMgr_TypeOfPresentation3d*:
bf62b306 464 * *PrsMgr_TOP_AllView*,
465 * *PrsMgr_TOP_ProjectorDependant*
72b7576f 466
7c42f3f4 467* Later by using the function *PrsMgr_PresentableObject::SetTypeOfPresentation*
72b7576f 468
7c42f3f4 469*AIS_Shape* class is an example of an interactive object that supports HLR representation.
470The type of the HLR algorithm is stored in *Prs3d_Drawer* of the shape. It is a value of the *Prs3d_TypeOfHLR* enumeration and can be set to:
471 * *Prs3d_TOH_PolyAlgo* for a polygonal algorithm based on the shape's triangulation;
472 * *Prs3d_TOH_Algo* for an exact algorithm that works with the shape's real geometry;
473 * *Prs3d_TOH_NotSet* if the type of algorithm is not set for the given interactive object instance.
72b7576f 474
7c42f3f4 475The type of the HLR algorithm used for *AIS_Shape* can be changed by calling the *AIS_Shape::SetTypeOfHLR()* method.
476The current HLR algorithm type can be obtained using *AIS_Shape::TypeOfHLR()* method is to be used.
72b7576f 477
7863dabb 478These methods get the value from the drawer of *AIS_Shape*. If the HLR algorithm type in the *Prs3d_Drawer* is set to *Prs3d_TOH_NotSet*, the *Prs3d_Drawer* gets the value from the default drawer of *AIS_InteractiveContext*.
7c42f3f4 479So 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.
72b7576f 480
bf62b306 481@subsubsection occt_visu_3_2_3 Presentation modes
72b7576f 482
7c42f3f4 483There are four types of interactive objects in AIS:
484 * the "construction element" or Datum,
485 * the Relation (dimensions and constraints)
486 * the Object
487 * the None type (when the object is of an unknown type).
72b7576f 488
7c42f3f4 489Inside 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:
490 * *AIS_InteractiveObject::Type*
491 * *AIS_InteractiveObject::Signature*.
72b7576f 492
7c42f3f4 493**Note** that some signatures are already used by "standard" objects provided in AIS (see the @ref occt_visu_3_5 "List of Standard Interactive Object Classes").
72b7576f 494
7c42f3f4 495The 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.
496Consequently, to get information about this class it is necessary to use virtual function *AIS_InteractiveObject::AcceptDisplayMode*.
72b7576f 497
bf62b306 498#### Display Mode
72b7576f 499
bf62b306 500The 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 501
bf62b306 502#### Highlight Mode
72b7576f 503
7c42f3f4 504At dynamic detection, the presentation echoed by the Interactive Context, is by default the presentation already on the screen.
72b7576f 505
7863dabb 506The 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 507
7c42f3f4 508Note 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 509
7c42f3f4 510For 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 511
bf62b306 512#### Infinite Status
7c42f3f4 513
514If you do not want an object to be affected by a *FitAll* view, you must declare it infinite; you can cancel its "infinite" status using *AIS_InteractiveObject::SetInfiniteState* and *AIS_InteractiveObject::IsInfinite* functions.
516Let us take for example the class called *IShape* representing an interactive object:
7863dabb 519myPk_IShape::myPk_IShape (const TopoDS_Shape& theShape, PrsMgr_TypeOfPresentation theType)
7c42f3f4 520: AIS_InteractiveObject (theType), myShape (theShape) { SetHilightMode (0); }
7863dabb 522Standard_Boolean myPk_IShape::AcceptDisplayMode (const Standard_Integer theMode) const
524 return theMode == 0 || theMode == 1;
7c42f3f4 527void myPk_IShape::Compute (const Handle(PrsMgr_PresentationManager3d)& thePrsMgr,
528 const Handle(Prs3d_Presentation)& thePrs,
529 const Standard_Integer theMode)
531 switch (theMode)
532 {
533 // algo for calculation of wireframe presentation
534 case 0: StdPrs_WFDeflectionShape::Add (thePrs, myShape, myDrawer); return;
535 // algo for calculation of shading presentation
536 case 1: StdPrs_ShadedShape::Add (thePrs, myShape, myDrawer); return;
537 }
540void myPk_IShape::Compute (const Handle(Prs3d_Projector)& theProjector,
541 const Handle(Prs3d_Presentation)& thePrs)
543 // Hidden line mode calculation algorithm
544 StdPrs_HLRPolyShape::Add (thePrs, myShape, myDrawer, theProjector);
bf62b306 545}
72b7576f 547
7c42f3f4 548@subsubsection occt_visu_3_2_4 Selection
72b7576f 549
7c42f3f4 550An 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 interactive object or shape which has been detected (see @ref occt_visu_2_2 "Selection" chapter).
72b7576f 551
7c42f3f4 552The set of sensitive primitives, which correspond to a given mode, is stocked in a **Selection** (*SelectMgr_Selection*).
72b7576f 553
7c42f3f4 554Each 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*. However, it can be modified in the custom interactive objects using method *SelectMgr_SelectableObject::setGlobalSelMode()*.
72b7576f 555
ebcbd824 556The calculation of selection primitives (or sensitive entities) is done in a virtual function *ComputeSelection*. It should be implemented for each type of interactive object that is assumed to have different selection modes using the function *AIS_InteractiveObject::ComputeSelection*.
a7d4dd94 557A detailed explanation of the mechanism and the manner of implementing this function has been given in @ref occt_visu_2_2 "Selection" chapter.
72b7576f 558
a7d4dd94 559There are some examples of selection mode calculation for the most widely used interactive object in OCCT -- *AIS_Shape* (selection by vertex, by edges, etc). To create new classes of interactive objects with the same selection behavior as *AIS_Shape* -- such as vertices and edges -- you must redefine the virtual function *AIS_InteractiveObject::AcceptShapeDecomposition*.
2683e647 560
bf62b306 561@subsubsection occt_visu_3_2_5 Graphic attributes
72b7576f 562
7c42f3f4 563Graphic attributes manager, or *Prs3d_Drawer*, stores graphic attributes for specific interactive objects and for interactive objects controlled by interactive context.
18006a0f 564
565Initially, all drawer attributes are filled out with the predefined values which will define the default 3D object appearance.
18006a0f 566When an interactive object is visualized, the required graphic attributes are first taken from its own drawer if one exists, or from the context drawer if no specific drawer for that type of object exists.
568Keep in mind the following points concerning graphic attributes:
7c42f3f4 569 * Each interactive object can have its own visualization attributes.
570 * 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.)
571 * 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 572
7c42f3f4 573@figure{visualization_image020.svg,"Redefinition of virtual functions for changes in AIS_Shape and AIS_TextLabel.",360}
72b7576f 574
7c42f3f4 575The following virtual functions provide settings for color, width, material and transparency:
576 * *AIS_InteractiveObject::UnsetColor*
577 * *AIS_InteractiveObject::SetWidth*
578 * *AIS_InteractiveObject::UnsetWidth*
579 * *AIS_InteractiveObject::SetMaterial*
580 * *AIS_InteractiveObject::UnsetMaterial*
581 * *AIS_InteractiveObject::SetTransparency*
582 * *AIS_InteractiveObject::UnsetTransparency*
72b7576f 583
7c42f3f4 584These methods can be used as a shortcut assigning properties in common way, but result might be not available.
585Some interactive objects might not implement these methods at all or implement only a sub-set of them.
586Direct modification of *Prs3d_Drawer* properties returned by *AIS_InteractiveObject::Attributes* can be used for more precise and predictable configuration.
72b7576f 587
7c42f3f4 588It is important to know which functions may imply the recalculation of presentations of the object.
589If the presentation mode of an interactive object is to be updated, a flag from *PrsMgr_PresentableObject* indicates this.
590The mode can be updated using the functions *Display* and *Redisplay* in *AIS_InteractiveContext*.
72b7576f 591
7c42f3f4 592@subsubsection occt_visu_3_2_6 Complementary Services
72b7576f 593
7c42f3f4 594When you use complementary services for interactive objects, pay special attention to the cases mentioned below.
72b7576f 595
bf62b306 596#### Change the location of an interactive object
72b7576f 597
7c42f3f4 598The following functions allow "moving" the representation and selection of Interactive Objects in a view without recalculation (and modification of the original shape).
599 * *AIS_InteractiveContext::SetLocation*
600 * *AIS_InteractiveContext::ResetLocation*
601 * *AIS_InteractiveContext::HasLocation*
602 * *AIS_InteractiveContext::Location*
72b7576f 603
7c42f3f4 604#### Connect an interactive object to an applicative entity
72b7576f 605
7863dabb 606Each Interactive Object has functions that allow attributing it an *GetOwner* in form of a *Transient*.
7c42f3f4 607 * *AIS_InteractiveObject::SetOwner*
608 * *AIS_InteractiveObject::HasOwner*
7863dabb 609 * *AIS_InteractiveObject::GetOwner*
72b7576f 610
7c42f3f4 611An interactive object can therefore be associated or not with an applicative entity, without affecting its behavior.
72b7576f 612
7863dabb 613**NOTE:** Don't be confused by owners of another kind - *SelectMgr_EntityOwner* used for identifying selectable parts of the object or object itself.
72b7576f 614
7c42f3f4 615#### Resolving coincident topology
72b7576f 616
7c42f3f4 617Due 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 618
7c42f3f4 619To 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 620
7c42f3f4 621The methods *AIS_InteractiveObject::SetPolygonOffsets* and *AIS_InteractiveContext::SetPolygonOffsets* allow setting up the polygon offsets.
ebcbd824 622
623@subsubsection occt_visu_3_2_7 Object hierarchy
625Each *PrsMgr_PresentableObject* has a list of objects called *myChildren*.
626Any transformation of *PrsMgr_PresentableObject* is also applied to its children. This hierarchy does not propagate to *Graphic3d* level and below.
628*PrsMgr_PresentableObject* sends its combined (according to the hierarchy) transformation down to *Graphic3d_Structure*.
ebcbd824 629The materials of structures are not affected by the hierarchy.
631Object hierarchy can be controlled by the following API calls:
7c42f3f4 632* *PrsMgr_PresentableObject::AddChild*;
633* *PrsMgr_PresentableObject::RemoveChild*.
ebcbd824 634
635@subsubsection occt_visu_3_2_8 Instancing
637The conception of instancing operates the object hierarchy as follows:
7c42f3f4 638* Instances are represented by separated *AIS* objects.
639* Instances do not compute any presentations.
ebcbd824 640
641Classes *AIS_ConnectedInteractive* and *AIS_MultipleConnectedInteractive* are used to implement this conception.
49225e2f 643*AIS_ConnectedInteractive* is an object instance, which reuses the geometry of the connected object but has its own transformation and visibility flag. This connection is propagated down to *OpenGl* level, namely to *OpenGl_Structure*. *OpenGl_Structure* can be connected only to a single other structure.
ebcbd824 644
7c42f3f4 645*AIS_ConnectedInteractive* can be referenced to any *AIS_InteractiveObject* in general. When it is referenced to another *AIS_ConnectedInteractive*, it just copies the reference.
ebcbd824 646
647*AIS_MultipleConnectedInteractive* represents an assembly, which does not have its own presentation. The assemblies are able to participate in the object hierarchy and are intended to handle a grouped set of instanced objects. It behaves as a single object in terms of selection. It applies high level transformation to all sub-elements since it is located above in the hierarchy.
649All *AIS_MultipleConnectedInteractive* are able to have child assemblies. Deep copy of object instances tree is performed if one assembly is attached to another.
651Note that *AIS_ConnectedInteractive* cannot reference *AIS_MultipleConnectedInteractive*. *AIS_ConnectedInteractive* copies sensitive entities of the origin object for selection, unlike *AIS_MultipleConnectedInteractive* that re-uses the entities of the origin object.
653Instances can be controlled by the following DRAW commands:
7c42f3f4 654* *vconnect* : Creates and displays *AIS_MultipleConnectedInteractive* object from input objects and location.
655* *vconnectto* : Makes an instance of object with the given position.
656* *vdisconnect* : Disconnects all objects from an assembly or disconnects an object by name or number.
657* *vaddconnected* : Adds an object to the assembly.
658* *vlistconnected* : Lists objects in the assembly.
ebcbd824 659
660Have a look at the examples below:
662pload ALL
664psphere s 1
665vdisplay s
666vconnectto s2 3 0 0 s # make instance
670See how proxy *OpenGl_Structure* is used to represent instance:
d6b4d3d0 672@figure{/user_guides/visualization/images/visualization_image029.png,"",240}
ebcbd824 673
674The original object does not have to be displayed in order to make instance. Also selection handles transformations of instances correctly:
677pload ALL
679psphere s 1
680psphere p 0.5
681vdisplay s # p is not displayed
682vsetloc s -2 0 0
683vconnect x 3 0 0 s p # make assembly
d6b4d3d0 687@figure{/user_guides/visualization/images/visualization_image030.png,"",420}
ebcbd824 688
689Here is the example of a more complex hierarchy involving sub-assemblies:
692pload ALL
694box b 1 1 1
695psphere s 0.5
696vdisplay b s
697vsetlocation s 0 2.5 0
698box d 0.5 0.5 3
699box d2 0.5 3 0.5
700vdisplay d d2
702vconnectto b1 -2 0 0 b
703vconnect z 2 0 0 b s
704vconnect z2 4 0 0 d d2
705vconnect z3 6 0 0 z z2
7c42f3f4 709@subsection occt_visu_3_3 Interactive Context
ebcbd824 710
7c42f3f4 711@subsubsection occt_visu_3_3_1 Rules
72b7576f 712
7c42f3f4 713The Interactive Context allows managing in a transparent way the graphic and **selectable** behavior of interactive objects in one or more viewers. Most functions which allow modifying the attributes of interactive objects, and which were presented in the preceding chapter, will be looked at again here.
72b7576f 714
7c42f3f4 715There 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 716
bf62b306 717~~~~~
7c42f3f4 718Handle(AIS_Shape) aShapePrs = new AIS_Shape (theShape);
719myIntContext->Display (aShapePrs, AIS_Shaded, 0, false, aShapePrs->AcceptShapeDecomposition());
720myIntContext->SetColor(aShapePrs, Quantity_NOC_RED);
bf62b306 721~~~~~
72b7576f 722
7c42f3f4 723You can also write
72b7576f 724
bf62b306 725~~~~~
7c42f3f4 726Handle(AIS_Shape) aShapePrs = new AIS_Shape (theShape);
727aShapePrs->SetColor (Quantity_NOC_RED);
728aShapePrs->SetDisplayMode (AIS_Shaded);
729myIntContext->Display (aShapePrs);
bf62b306 730~~~~~
72b7576f 731
7c42f3f4 732@subsubsection occt_visu_3_3_2 Groups of functions
72b7576f 733
7c42f3f4 734**Neutral Point** and **Local Selection** constitute the two operating modes or states of the **Interactive Context**, which is the central entity which pilots visualizations and selections.
735The **Neutral Point**, which is the default mode, allows easily visualizing and selecting interactive objects, which have been loaded into the context.
736Activating **Local Selection** for specific Objects allows selecting of their sub-parts.
72b7576f 737
7c42f3f4 738@subsubsection occt_visu_3_3_3 Management of the Interactive Context
18006a0f 739
740An interactive object can have a certain number of specific graphic attributes, such as visualization mode, color, and material. Correspondingly, the interactive context has a set of graphic attributes, the *Drawer*, which is valid by default for the objects it controls.
7c42f3f4 741When an interactive object is visualized, the required graphic attributes are first taken from the object's own *Drawer* if it exists, or from the context drawer if otherwise.
18006a0f 742
7c42f3f4 743The following adjustable settings allow personalizing the behavior of presentations and selections:
744 * Default Drawer, containing all the color and line attributes which can be used by interactive objects, which do not have their own attributes.
745 * Default Visualization Mode for interactive objects. By default: *mode 0*;
746 * Highlight color of entities detected by mouse movement. By default: *Quantity_NOC_CYAN1*;
747 * Pre-selection color. By default: *Quantity_NOC_GREEN*;
748 * Selection color (when you click on a detected object). By default: *Quantity_NOC_GRAY80*;
72b7576f 749
7c42f3f4 750All of these settings can be modified by functions proper to the Context.
751When 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.
18006a0f 752
7c42f3f4 753Let us examine the case of two interactive objects: *theObj1* and *theObj2*:
72b7576f 754
bf62b306 755~~~~~
7c42f3f4 756theCtx->Display (theObj1, false);
757theCtx->Display (theObj2, true); // TRUE for viewer update
758theCtx->SetDisplayMode (theObj1, 3, false);
759theCtx->SetDisplayMode (2, true);
760// theObj2 is visualised in mode 2 (if it accepts this mode)
761// theObj1 stays visualised in its mode 3
bf62b306 762~~~~~
72b7576f 763
7c42f3f4 764*PresentationManager* and *Selector3D*, which manage the presentation and selection of present interactive objects, are associated to the main Viewer.
72b7576f 765
7863dabb 766*WARNING!* Do NOT use integer values (like in sample above) in real code - use appropriate enumerations instead!
767Each presentable object has independent list of supported display and selection modes; for instance, *AIS_DisplayMode* enumeration is applicable only to *AIS_Shape* presentations.
7c42f3f4 769@subsection occt_visu_3_4 Local Selection
72b7576f 770
7c42f3f4 771@subsubsection occt_visu_3_4_1 Selection Modes
72b7576f 772
7c42f3f4 773The Local Selection is defined by index (Selection Mode). The Selection Modes implemented by a specific interactive object and their meaning should be checked within the documentation of this class.
774See, for example, *MeshVS_SelectionModeFlags* for *MeshVS_Mesh* object.
72b7576f 775
14deaf42 776*AIS_Shape* is the most used interactive object. It provides API to manage selection operations on the constituent elements of shapes (selection of vertices, edges, faces, etc.). The Selection Mode for a specific shape type (*TopAbs_ShapeEnum*) is returned by method *AIS_Shape::SelectionMode()*.
72b7576f 777
7863dabb 778The method *AIS_InteractiveContext::Display()* without a Selection Mode argument activates the default Selection Mode of the object.
14deaf42 779The methods *AIS_InteractiveContext::Activate()* and *AIS_InteractiveContext::Deactivate()* activate and deactivate a specific Selection Mode.
72b7576f 780
7c42f3f4 781More than one Selection Mode can be activated at the same time (but default 0 mode for selecting entire object is exclusive - it cannot be combined with others).
782The list of active modes can be retrieved using function *AIS_InteractiveContext::ActivatedModes*.
72b7576f 783
7c42f3f4 784@subsubsection occt_visu_3_4_2 Filters
bf62b306 785
7c42f3f4 786To define an environment of dynamic detection, you can use standard filter classes or create your own.
787A filter questions the owner of the sensitive primitive to determine if it has the desired qualities. If it answers positively, it is kept. If not, it is rejected.
bf62b306 788
7c42f3f4 789The 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 selector answer *OK*. If so, it is kept, otherwise it is rejected.
790You can create a custom class of filter objects by implementing the deferred function *SelectMgr_Filter::IsOk()*.
72b7576f 791
7c42f3f4 792In *SelectMgr*, there are also Composition filters (AND Filters, OR Filters), which allow combining several filters. In Interactive Context, all filters that you add are stored in an OR filter (which answers *OK* if at least one filter answers *OK*).
72b7576f 793
7c42f3f4 794There are Standard filters, which have already been implemented in several packages:
795 * *StdSelect_EdgeFilter* -- for edges, such as lines and circles;
796 * *StdSelect_FaceFilter* -- for faces, such as planes, cylinders and spheres;
797 * *StdSelect_ShapeTypeFilter* -- for shape types, such as compounds, solids, shells and wires;
798 * *AIS_TypeFilter* -- for types of interactive objects;
799 * *AIS_SignatureFilter* -- for types and signatures of interactive objects;
800 * *AIS_AttributeFilter* -- for attributes of Interactive Objects, such as color and width.
72b7576f 801
7c42f3f4 802There are several functions to manipulate filters:
803* *AIS_InteractiveContext::AddFilter* adds a filter passed as an argument.
804* *AIS_InteractiveContext::RemoveFilter* removes a filter passed as an argument.
805* *AIS_InteractiveContext::RemoveFilters* removes all present filters.
806* *AIS_InteractiveContext::Filters* gets the list of filters active in a context.
72b7576f 807
7c42f3f4 808#### Example
72b7576f 809
bf62b306 810~~~~~
7c42f3f4 811// shading visualization mode, no specific mode, authorization for decomposition into sub-shapes
812const TopoDS_Shape theShape;
813Handle(AIS_Shape) aShapePrs = new AIS_Shape (theShape);
814myContext->Display (aShapePrs, AIS_Shaded, -1, true, true);
72b7576f 815
7c42f3f4 816// activates decomposition of shapes into faces
817const int aSubShapeSelMode = AIS_Shape::SelectionMode (TopAbs_Face);
818myContext->Activate (aShapePrs, aSubShapeSelMode);
72b7576f 819
7c42f3f4 820Handle(StdSelect_FaceFilter) aFil1 = new StdSelect_FaceFilter (StdSelect_Revol);
821Handle(StdSelect_FaceFilter) aFil2 = new StdSelect_FaceFilter (StdSelect_Plane);
822myContext->AddFilter (aFil1);
823myContext->AddFilter (aFil2);
72b7576f 824
7c42f3f4 825// only faces of revolution or planar faces will be selected
7863dabb 826myContext->MoveTo (thePixelX, thePixelY, myView, true);
bf62b306 827~~~~~
72b7576f 828
7c42f3f4 829@subsubsection occt_visu_3_4_6 Selection
72b7576f 830
7c42f3f4 831Dynamic detection and selection are put into effect in a straightforward way. There are only a few conventions and functions to be familiar with:
832 * *AIS_InteractiveContext::MoveTo* -- passes mouse position to Interactive Context selectors.
833 * *AIS_InteractiveContext::Select* -- stores what has been detected at the last *MoveTo*. Replaces the previously selected object. Empties the stack if nothing has been detected at the last move.
834 * *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.
835 * *AIS_InteractiveContext::Select* -- selects everything found in the surrounding area.
836 * *AIS_InteractiveContext::ShiftSelect* -- selects what was not previously in the list of selected, deselects those already present.
bf62b306 837
7c42f3f4 838Highlighting of detected and selected entities is automatically managed by the Interactive Context. The Highlight colors are those dealt with above. You can nonetheless disconnect this automatic mode if you want to manage this part yourself:
bf62b306 839~~~~~
7c42f3f4 840 AIS_InteractiveContext::SetAutomaticHilight
841 AIS_InteractiveContext::AutomaticHilight
bf62b306 842~~~~~
72b7576f 843
7c42f3f4 844You can question the Interactive context by moving the mouse. The following functions can be used:
845 * *AIS_InteractiveContext::HasDetected* -- checks if there is a detected entity;
846 * *AIS_InteractiveContext::DetectedOwner* -- returns the (currently highlighted) detected entity.
bf62b306 847
7c42f3f4 848After using the *Select* and *ShiftSelect* functions, you can explore the list of selections. The following functions can be used:
849 * *AIS_InteractiveContext::InitSelected* -- initializes an iterator;
850 * *AIS_InteractiveContext::MoreSelected* -- checks if the iterator is valid;
851 * *AIS_InteractiveContext::NextSelected* -- moves the iterator to the next position;
852 * *AIS_InteractiveContext::SelectedOwner* -- returns an entity at the current iterator position.
72b7576f 853
14deaf42 854The owner object *SelectMgr_EntityOwner* is a key object identifying the selectable entity in the viewer (returned by methods *AIS_InteractiveContext::DetectedOwner* and *AIS_InteractiveContext::SelectedOwner*).
855The Interactive Object itself can be retrieved by method *SelectMgr_EntityOwner::Selectable*, while identifying a sub-part depends on the type of Interactive Object.
7c42f3f4 856In case of *AIS_Shape*, the (sub)shape is returned by method *StdSelect_BRepOwner::Shape*.
72b7576f 857
7c42f3f4 858#### Example
7863dabb 859
bf62b306 860~~~~~
7c42f3f4 861for (myAISCtx->InitSelected(); myAISCtx->MoreSelected(); myAISCtx->NextSelected())
bf62b306 862{
7c42f3f4 863 Handle(SelectMgr_EntityOwner) anOwner = myAISCtx->SelectedOwner();
864 Handle(AIS_InteractiveObject) anObj = Handle(AIS_InteractiveObject)::DownCast (anOwner->Selectable());
865 if (Handle(StdSelect_BRepOwner) aBRepOwner = Handle(StdSelect_BRepOwner)::DownCast (anOwner))
866 {
867 // to be able to use the picked shape
868 TopoDS_Shape aShape = aBRepOwner->Shape();
869 }
bf62b306 870}
72b7576f 872
7c42f3f4 873@subsection occt_visu_3_5 Standard Interactive Object Classes
72b7576f 874
18006a0f 875Interactive Objects are selectable and viewable objects connecting graphic representation and the underlying reference geometry.
877They are divided into four types:
3f812249 878 * the **Datum** -- a construction geometric element;
879 * the **Relation** -- a constraint on the interactive shape and the corresponding reference geometry;
880 * the **Object** -- a topological shape or connection between shapes;
881 * **None** -- a token, that instead of eliminating the object, tells the application to look further until it finds an acceptable object definition in its generation.
18006a0f 882
883Inside these categories, there is a possibility of additional characterization by means of a signature. The signature provides an index to the further characterization. By default, the **Interactive Object** has a *None* type and a signature of 0 (equivalent to *None*).
7c42f3f4 884If you want to give a particular type and signature to your interactive object, you must redefine the two virtual methods: *Type* and *Signature*.
18006a0f 885
886@subsubsection occt_visu_3_5_1 Datum
888The **Datum** groups together the construction elements such as lines, circles, points, trihedrons, plane trihedrons, planes and axes.
7c42f3f4 889
890*AIS_Point, AIS_Axis, AIS_Line, AIS_Circle, AIS_Plane* and *AIS_Trihedron* have four selection modes:
7863dabb 891 * mode AIS_TrihedronSelectionMode_EntireObject : selection of a trihedron;
892 * mode AIS_TrihedronSelectionMode_Origin : selection of the origin of the trihedron;
893 * mode AIS_TrihedronSelectionMode_Axes : selection of the axes;
894 * mode AIS_TrihedronSelectionMode_MainPlanes : selection of the planes XOY, YOZ, XOZ.
7c42f3f4 895
7863dabb 896when you activate one of modes, you pick AIS objects of type:
7c42f3f4 897 * *AIS_Point*;
898 * *AIS_Axis* (and information on the type of axis);
899 * *AIS_Plane* (and information on the type of plane).
901*AIS_PlaneTrihedron* offers three selection modes:
902 * mode 0 : selection of the whole trihedron;
903 * mode 1 : selection of the origin of the trihedron;
3f812249 904 * mode 2 : selection of the axes -- same remarks as for the Trihedron.
72b7576f 905
7c42f3f4 906For the presentation of planes and trihedra, the default length unit is millimeter and the default value for the representation of axes is 10. To modify these dimensions, you must temporarily recover the object **Drawer**. From it, take the *DatumAspect()* and change the value *FirstAxisLength*. Finally, recalculate the presentation.
e5bd0d98 907
18006a0f 908@subsubsection occt_visu_3_5_2 Object
910The **Object** type includes topological shapes, and connections between shapes.
e5bd0d98 911
7c42f3f4 912*AIS_Shape* has two visualization modes:
7863dabb 913 * mode AIS_WireFrame : Line (default mode)
914 * mode AIS_Shaded : Shading (depending on the type of shape)
72b7576f 915
7c42f3f4 916*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.
917*AIS_MultipleConnectedInteractive* is an object connected to a list of interactive objects (which can also be Connected objects. It does not require memory-hungry presentation calculations).
72b7576f 918
7c42f3f4 919*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.
18006a0f 920
921The class *AIS_ColoredShape* allows using custom colors and line widths for *TopoDS_Shape* objects and their sub-shapes.
924 AIS_ColoredShape aColoredShape = new AIS_ColoredShape (theShape);
926 // setup color of entire shape
7c42f3f4 927 aColoredShape->SetColor (Quantity_NOC_RED);
18006a0f 928
929 // setup line width of entire shape
930 aColoredShape->SetWidth (1.0);
932 // set transparency value
933 aColoredShape->SetTransparency (0.5);
935 // customize color of specified sub-shape
7c42f3f4 936 aColoredShape->SetCustomColor (theSubShape, Quantity_NOC_BLUE1);
18006a0f 937
938 // customize line width of specified sub-shape
939 aColoredShape->SetCustomWidth (theSubShape, 0.25);
942The presentation class *AIS_PointCloud* can be used for efficient drawing of large arbitrary sets of colored points. It uses *Graphic3d_ArrayOfPoints* to pass point data into OpenGl graphic driver to draw a set points as an array of "point sprites". The point data is packed into vertex buffer object for performance.
943- The type of point marker used to draw points can be specified as a presentation aspect.
944- The presentation provides selection by a bounding box of the visualized set of points. It supports two display / highlighting modes: points or bounding box.
d6b4d3d0 946@figure{point_cloud.png,"A random colored cloud of points",240}
18006a0f 947
950Handle(Graphic3d_ArrayOfPoints) aPoints = new Graphic3d_ArrayOfPoints (2000, Standard_True);
951aPoints->AddVertex (gp_Pnt(-40.0, -40.0, -40.0), Quantity_Color (Quantity_NOC_BLUE1));
952aPoints->AddVertex (gp_Pnt (40.0, 40.0, 40.0), Quantity_Color (Quantity_NOC_BLUE2));
954Handle(AIS_PointCloud) aPntCloud = new AIS_PointCloud();
955aPntCloud->SetPoints (aPoints);
958The draw command *vpointcloud* builds a cloud of points from shape triangulation.
959This command can also draw a sphere surface or a volume with a large amount of points (more than one million).
bf62b306 961@subsubsection occt_visu_3_5_3 Relations
18006a0f 962
963The **Relation** is made up of constraints on one or more interactive shapes and the corresponding reference geometry. For example, you might want to constrain two edges in a parallel relation. This constraint is considered as an object in its own right, and is shown as a sensitive primitive. This takes the graphic form of a perpendicular arrow marked with the || symbol and lying between the two edges.
787ff240 965The following relations are provided by *PrsDim*:
966 * *PrsDim_ConcentricRelation*
967 * *PrsDim_FixRelation*
968 * *PrsDim_IdenticRelation*
969 * *PrsDim_ParallelRelation*
970 * *PrsDim_PerpendicularRelation*
971 * *PrsDim_Relation*
972 * *PrsDim_SymmetricRelation*
973 * *PrsDim_TangentRelation*
72b7576f 974
7c42f3f4 975The list of relations is not exhaustive.
72b7576f 976
bf62b306 977@subsubsection occt_visu_3_5_4 Dimensions
787ff240 978 * *PrsDim_AngleDimension*
979 * *PrsDim_Chamf3dDimension*
980 * *PrsDim_DiameterDimension*
981 * *PrsDim_DimensionOwner*
982 * *PrsDim_LengthDimension*
983 * *PrsDim_OffsetDimension*
984 * *PrsDim_RadiusDimension*
72b7576f 985
7c42f3f4 986@subsubsection occt_visu_3_5_5 MeshVS_Mesh
72b7576f 987
7c42f3f4 988*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 989
7c42f3f4 990However, 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 991
7c42f3f4 992The 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 993
7c42f3f4 994You can add/remove builders using the following methods:
bf62b306 995~~~~~
7c42f3f4 996 MeshVS_Mesh::AddBuilder (const Handle(MeshVS_PrsBuilder)& theBuilder, Standard_Boolean theToTreatAsHilighter);
997 MeshVS_Mesh::RemoveBuilder (const Standard_Integer theIndex);
998 MeshVS_Mesh::RemoveBuilderById (const Standard_Integer theId);
bf62b306 999~~~~~
72b7576f 1000
7c42f3f4 1001There 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:
bf62b306 1002~~~~~
1003 MeshVS_DMF_WireFrame
1004 MeshVS_DMF_Shading
1005 MeshVS_DMF_Shrink
7c42f3f4 1006~~~~~
72b7576f 1007
7c42f3f4 1008It is also possible to display deformed mesh in wireframe, shading or shrink modes usung:
1010 MeshVS_DMF_DeformedPrsWireFrame
1011 MeshVS_DMF_DeformedPrsShading
1012 MeshVS_DMF_DeformedPrsShrink
bf62b306 1013~~~~~
72b7576f 1014
7c42f3f4 1015The following methods represent different kinds of data:
bf62b306 1016~~~~~
7c42f3f4 1017 MeshVS_DMF_VectorDataPrs
bf62b306 1018 MeshVS_DMF_NodalColorDataPrs
1019 MeshVS_DMF_ElementalColorDataPrs
1020 MeshVS_DMF_TextDataPrs
1021 MeshVS_DMF_EntitiesWithData
7c42f3f4 1022~~~~~
bf62b306 1023
7c42f3f4 1024The following methods provide selection and highlighting:
bf62b306 1025~~~~~
1026 MeshVS_DMF_SelectionPrs
1027 MeshVS_DMF_HilightPrs
7c42f3f4 1028~~~~~
72b7576f 1029
7c42f3f4 1030*MeshVS_DMF_User* is a user-defined mode.
72b7576f 1031
7c42f3f4 1032These values will be used by the presentation builder.
1033There is also a set of selection modes flags that can be grouped in a combination of bits:
bf62b306 1034 * *MeshVS_SMF_0D*
1035 * *MeshVS_SMF_Link*
1036 * *MeshVS_SMF_Face*
1037 * *MeshVS_SMF_Volume*
7c42f3f4 1038 * *MeshVS_SMF_Element* -- groups *0D, Link, Face* and *Volume* as a bit mask;
bf62b306 1039 * *MeshVS_SMF_Node*
7c42f3f4 1040 * *MeshVS_SMF_All* -- groups *Element* and *Node* as a bit mask;
bf62b306 1041 * *MeshVS_SMF_Mesh*
1042 * *MeshVS_SMF_Group*
7c42f3f4 1044Such an object, for example, can be used for displaying the object and stored in the STL file format:
72b7576f 1045
bf62b306 1046~~~~~
1047// read the data and create a data source
4178b353 1048Handle(Poly_Triangulation) aSTLMesh = RWStl::ReadFile (aFileName);
1049Handle(XSDRAWSTLVRML_DataSource) aDataSource = new XSDRAWSTLVRML_DataSource (aSTLMesh);
72b7576f 1050
7c42f3f4 1051// create mesh
1052Handle(MeshVS_Mesh) aMeshPrs = new MeshVS();
1053aMeshPrs->SetDataSource (aDataSource);
72b7576f 1054
bf62b306 1055// use default presentation builder
7c42f3f4 1056Handle(MeshVS_MeshPrsBuilder) aBuilder = new MeshVS_MeshPrsBuilder (aMeshPrs);
1057aMeshPrs->AddBuilder (aBuilder, true);
bf62b306 1058~~~~~
72b7576f 1059
7c42f3f4 1060*MeshVS_NodalColorPrsBuilder* allows representing a mesh with a color scaled texture mapped on it.
1061To do this you should define a color map for the color scale, pass this map to the presentation builder, and define an appropriate value in the range of 0.0 - 1.0 for every node.
1062The following example demonstrates how you can do this (check if the view has been set up to display textures):
bf62b306 1063
1065// assign nodal builder to the mesh
7c42f3f4 1066Handle(MeshVS_NodalColorPrsBuilder) aBuilder = new MeshVS_NodalColorPrsBuilder (theMeshPrs, MeshVS_DMF_NodalColorDataPrs | MeshVS_DMF_OCCMask);
1067aBuilder->UseTexture (true);
bf62b306 1068
1069// prepare color map
7c42f3f4 1070Aspect_SequenceOfColor aColorMap;
1071aColorMap.Append (Quantity_NOC_RED);
1072aColorMap.Append (Quantity_NOC_BLUE1);
bf62b306 1073
1074// assign color scale map values (0..1) to nodes
7c42f3f4 1075TColStd_DataMapOfIntegerReal aScaleMap;
2683e647 1076...
bf62b306 1077// iterate through the nodes and add an node id and an appropriate value to the map
7c42f3f4 1078aScaleMap.Bind (anId, aValue);
bf62b306 1080// pass color map and color scale values to the builder
7c42f3f4 1081aBuilder->SetColorMap (aColorMap);
1082aBuilder->SetInvalidColor (Quantity_NOC_BLACK);
1083aBuilder->SetTextureCoords (aScaleMap);
1084aMesh->AddBuilder (aBuilder, true);
bf62b306 1085~~~~~
72b7576f 1086
7c42f3f4 1087@subsection occt_visu_3_6 Dynamic Selection
72b7576f 1088
7c42f3f4 1089The dynamic selection represents the topological shape, which you want to select, by decomposition of *sensitive primitives* -- the sub-parts of the shape that will be detected and highlighted. The sets of these primitives are handled by the powerful three-level BVH tree selection algorithm.
72b7576f 1090
07f2b741 1091For more details on the algorithm and examples of usage, refer to @ref occt_visu_2_2 "Selection" chapter.
72b7576f 1092
bf62b306 1093@section occt_visu_4 3D Presentations
72b7576f 1094
7c42f3f4 1095@subsection occt_visu_4_1 Glossary of 3D terms
72b7576f 1096
7c42f3f4 1097* **Group** -- a set of primitives and attributes on those primitives. Primitives and attributes may be added to a group but cannot be removed from it, unless erased globally. A group can have a pick identity.
3f812249 1098* **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.
1099* **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.
7c42f3f4 1100* **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.
1101* **View** -- is defined by a view orientation, a view mapping, and a context view.
3f812249 1102* **Viewer** -- manages a set of views.
1103* **View orientation** -- defines the manner in which the observer looks at the scene in terms of View Reference Coordinates.
1104* **View mapping** -- defines the transformation from View Reference Coordinates to the Normalized Projection Coordinates. This follows the Phigs scheme.
1105* **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 1106
18006a0f 1107@subsection occt_visu_4_2 Graphic primitives
72b7576f 1108
18006a0f 1109The *Graphic3d* package is used to create 3D graphic objects in a 3D viewer. These objects called **structures** are made up of groups of primitives and attributes, such as polylines, planar polygons with or without holes, text and markers, and attributes, such as color, transparency, reflection, line type, line width, and text font. A group is the smallest editable element of a structure. A transformation can be applied to a structure. Structures can be connected to form a tree of structures, composed by transformations. Structures are globally manipulated by the viewer.
72b7576f 1110
7c42f3f4 1111Graphic structures can be:
1112 * Displayed,
1113 * Highlighted,
1114 * Erased,
1115 * Transformed,
18006a0f 1116 * Connected to form a tree hierarchy of structures, created by transformations.
7c42f3f4 1117
1118There are classes for:
1119 * Visual attributes for lines, faces, markers, text, materials,
1120 * Vectors and vertices,
1121 * Graphic objects, groups, and structures.
72b7576f 1122
18006a0f 1123@subsubsection occt_visu_4_2_2 Structure hierarchies
bf62b306 1124
18006a0f 1125The 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.
1127@subsubsection occt_visu_4_2_3 Graphic primitives
7c42f3f4 1128* **Markers**
1129 * Have one or more vertices,
1130 * Have a type, a scale factor, and a color,
1131 * Have a size, shape, and orientation independent of transformations.
1132* **Triangulation**
14deaf42 1133 * Has at least three vertices,
1134 * Has nodal normals defined for shading,
1135 * Has interior attributes -- style, color, front and back material, texture and reflection ratio.
7c42f3f4 1136* **Polylines** or **Segments**
1137 * Have two or more vertices,
1138 * Have the following attributes -- type, width scale factor, color.
1139* **Text**
1140 * Has geometric and non-geometric attributes,
1141 * Geometric attributes -- character height, character up vector, text path, horizontal and vertical alignment, orientation, three-dimensional position, zoomable flag
1142 * Non-geometric attributes -- text font, character spacing, character expansion factor, color.
1144@subsubsection occt_visu_4_2_4 Primitive arrays
1146The different types of primitives could be presented with the following primitive arrays:
bf62b306 1147 * *Graphic3d_ArrayOfPoints,*
bf62b306 1148 * *Graphic3d_ArrayOfPolylines,*
bf62b306 1149 * *Graphic3d_ArrayOfSegments,*
1150 * *Graphic3d_ArrayOfTriangleFans,*
1151 * *Graphic3d_ArrayOfTriangles,*
1152 * *Graphic3d_ArrayOfTriangleStrips.*
7c42f3f4 1154The *Graphic3d_ArrayOfPrimitives* is a base class for these primitive arrays.
1155Method set *Graphic3d_ArrayOfPrimitives::AddVertex* allows adding vertices to the primitive array with their attributes (color, normal, texture coordinates).
1156You can also modify the values assigned to the vertex or query these values by the vertex index.
bf62b306 1157
7c42f3f4 1158The following example shows how to define an array of points:
72b7576f 1159
bf62b306 1160~~~~~
1161// create an array
7c42f3f4 1162Handle(Graphic3d_ArrayOfPoints) anArray = new Graphic3d_ArrayOfPoints (theVerticiesMaxCount);
bf62b306 1163
1164// add vertices to the array
7c42f3f4 1165anArray->AddVertex (10.0, 10.0, 10.0);
1166anArray->AddVertex (0.0, 10.0, 10.0);
72b7576f 1167
bf62b306 1168// add the array to the structure
7c42f3f4 1169Handle(Graphic3d_Group) aGroup = thePrs->NewGroup();
1170aGroup->AddPrimitiveArray (anArray);
1171aGroup->SetGroupPrimitivesAspect (myDrawer->PointAspect()->Aspect());
bf62b306 1172~~~~~
72b7576f 1173
7c42f3f4 1174If the primitives share the same vertices (polygons, triangles, etc.) then you can define them as indices of the vertices array.
1175The method *Graphic3d_ArrayOfPrimitives::AddEdge* allows defining the primitives by indices. This method adds an "edge" in the range *[1, VertexNumber()]* in the array.
1176It is also possible to query the vertex defined by an edge using method *Graphic3d_ArrayOfPrimitives::Edge*.
72b7576f 1177
7c42f3f4 1178The following example shows how to define an array of triangles:
72b7576f 1179
bf62b306 1180~~~~~
1181// create an array
7c42f3f4 1182Standard_Boolean hasNormals = false;
1183Standard_Boolean hasColors = false;
1184Standard_Boolean hasTextureCrds = false;
1185Handle(Graphic3d_ArrayOfTriangles) anArray = new Graphic3d_ArrayOfTriangles (theVerticesMaxCount, theEdgesMaxCount, hasNormals, hasColors, hasTextureCrds);
bf62b306 1186// add vertices to the array
7c42f3f4 1187anArray->AddVertex (-1.0, 0.0, 0.0); // vertex 1
1188anArray->AddVertex ( 1.0, 0.0, 0.0); // vertex 2
1189anArray->AddVertex ( 0.0, 1.0, 0.0); // vertex 3
1190anArray->AddVertex ( 0.0,-1.0, 0.0); // vertex 4
bf62b306 1191
1192// add edges to the array
7c42f3f4 1193anArray->AddEdge (1); // first triangle
1194anArray->AddEdge (2);
1195anArray->AddEdge (3);
1196anArray->AddEdge (1); // second triangle
1197anArray->AddEdge (2);
1198anArray->AddEdge (4);
bf62b306 1199
1200// add the array to the structure
7c42f3f4 1201Handle(Graphic3d_Group) aGroup = thePrs->NewGroup();
1202aGroup->AddPrimitiveArray (anArray);
1203aGroup->SetGroupPrimitivesAspect (myDrawer->ShadingAspect()->Aspect());
bf62b306 1204~~~~~
18006a0f 1206@subsubsection occt_visu_4_2_5 Text primitive
72b7576f 1207
7863dabb 1208*TKOpenGl* toolkit renders text labels using texture fonts. *Graphic3d* text primitives have the following features:
7c42f3f4 1209 * fixed size (non-zoomable) or zoomable,
72b7576f 1210 * can be rotated to any angle in the view plane,
1211 * support unicode charset.
7c42f3f4 1213The text attributes for the group could be defined with the *Graphic3d_AspectText3d* attributes group.
1214To add any text to the graphic structure you can use the following methods:
7863dabb 1216void Graphic3d_Group::AddText (const Handle(Graphic3d_Text)& theTextParams,
1217 const Standard_Boolean theToEvalMinMax);
14deaf42 1219
7c42f3f4 1220You can pass FALSE as *theToEvalMinMax* if you do not want the graphic3d structure boundaries to be affected by the text position.
1222**Note** that the text orientation angle can be defined by *Graphic3d_AspectText3d* attributes.
72b7576f 1223
bf62b306 1224See the example:
1226// get the group
7c42f3f4 1227Handle(Graphic3d_Group) aGroup = thePrs->NewGroup();
72b7576f 1228
7c42f3f4 1229// change the text aspect
1230Handle(Graphic3d_AspectText3d) aTextAspect = new Graphic3d_AspectText3d();
1231aTextAspect->SetTextZoomable (true);
1232aTextAspect->SetTextAngle (45.0);
1233aGroup->SetPrimitivesAspect (aTextAspect);
72b7576f 1234
7c42f3f4 1235// add a text primitive to the structure
7863dabb 1236Handle(Graphic3d_Text) aText = new Graphic3d_Text (16.0f);
1237aText->SetText ("Text");
1238aText->SetPosition (gp_Pnt (1, 1, 1));
1239aGroup->AddText (aText);
bf62b306 1240~~~~~
18006a0f 1242@subsubsection occt_visu_4_2_6 Materials
1244A *Graphic3d_MaterialAspect* is defined by:
1245 * Transparency;
3f812249 1246 * Diffuse reflection -- a component of the object color;
18006a0f 1247 * Ambient reflection;
3f812249 1248 * Specular reflection -- a component of the color of the light source;
18006a0f 1249 * Refraction index.
1251The following items are required to determine the three colors of reflection:
1252 * Color;
1253 * Coefficient of diffuse reflection;
1254 * Coefficient of ambient reflection;
1255 * Coefficient of specular reflection.
1257@subsubsection occt_visu_4_2_7 Textures
1259A *texture* is defined by a name.
1260Three types of texture are available:
1261 * 1D;
1262 * 2D;
1263 * Environment mapping.
1265@subsubsection occt_visu_4_2_8 Shaders
7c42f3f4 1267OCCT visualization core supports GLSL shaders. Shaders can be assigned to a generic presentation by its drawer attributes (Graphic3d aspects). To enable custom shader for a specific AIS_Shape in your application, the following API functions can be used:
18006a0f 1268
1270// Create shader program
1271Handle(Graphic3d_ShaderProgram) aProgram = new Graphic3d_ShaderProgram();
1273// Attach vertex shader
7c42f3f4 1274aProgram->AttachShader (Graphic3d_ShaderObject::CreateFromFile (Graphic3d_TOS_VERTEX, "<Path to VS>"));
18006a0f 1275
1276// Attach fragment shader
7c42f3f4 1277aProgram->AttachShader (Graphic3d_ShaderObject::CreateFromFile (Graphic3d_TOS_FRAGMENT, "<Path to FS>"));
18006a0f 1278
1279// Set values for custom uniform variables (if they are)
7c42f3f4 1280aProgram->PushVariable ("MyColor", Graphic3d_Vec3 (0.0f, 1.0f, 0.0f));
18006a0f 1281
7c42f3f4 1282// Set aspect property for specific AIS_Shape
18006a0f 1283theAISShape->Attributes()->ShadingAspect()->Aspect()->SetShaderProgram (aProgram);
72b7576f 1285
18006a0f 1286@subsection occt_visu_4_3 Graphic attributes
72b7576f 1287
18006a0f 1288@subsubsection occt_visu_4_3_1 Aspect package overview
72b7576f 1289
18006a0f 1290The *Aspect* package provides classes for the graphic elements in the viewer:
1291 * Groups of graphic attributes;
1292 * Edges, lines, background;
1293 * Window;
1294 * Driver;
1295 * Enumerations for many of the above.
72b7576f 1296
18006a0f 1297@subsection occt_visu_4_4 3D view facilities
72b7576f 1298
18006a0f 1299@subsubsection occt_visu_4_4_1 Overview
72b7576f 1300
7c42f3f4 1301The *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 1302
7c42f3f4 1303A 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, etc.) in any particular view.
bf62b306 1304
7c42f3f4 1305The *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:
1306 * Default parameters of the viewer,
1307 * Views (orthographic, perspective),
1308 * Lighting (positional, directional, ambient, spot, headlight),
89a929ea 1309 * Clipping planes,
7c42f3f4 1310 * Instantiated sequences of views, planes, light sources, graphic structures, and picks,
1311 * Various package methods.
72b7576f 1312
18006a0f 1313@subsubsection occt_visu_4_4_2 A programming example
72b7576f 1314
cfece3ef 1315This sample TEST program for the *V3d* Package uses primary packages *Xw* and *Graphic3d* and secondary packages *Visual3d, Aspect, Quantity* and *math*.
7c42f3f4 1318// create a default display connection
cfece3ef 1319Handle(Aspect_DisplayConnection) aDispConnection = new Aspect_DisplayConnection();
7c42f3f4 1320// create a Graphic Driver
cfece3ef 1321Handle(OpenGl_GraphicDriver) aGraphicDriver = new OpenGl_GraphicDriver (aDispConnection);
7c42f3f4 1322// create a Viewer to this Driver
cfece3ef 1323Handle(V3d_Viewer) VM = new V3d_Viewer (aGraphicDriver);
1324VM->SetDefaultBackgroundColor (Quantity_NOC_DARKVIOLET);
1325VM->SetDefaultViewProj (V3d_Xpos);
1326// Create a structure in this Viewer
1327Handle(Graphic3d_Structure) aStruct = new Graphic3d_Structure (VM->Viewer());
1329// Type of structure
1330aStruct->SetVisual (Graphic3d_TOS_SHADING);
4ee1bdf4 1331
1332// Create a group of primitives in this structure
cfece3ef 1333Handle(Graphic3d_Group) aPrsGroup = new Graphic3d_Group (aStruct);
72b7576f 1334
cfece3ef 1335// Fill this group with one quad of size 100
1336Handle(Graphic3d_ArrayOfTriangleStrips) aTriangles = new Graphic3d_ArrayOfTriangleStrips (4);
1337aTriangles->AddVertex (-100./2., -100./2., 0.0);
1338aTriangles->AddVertex (-100./2., 100./2., 0.0);
1339aTriangles->AddVertex ( 100./2., -100./2., 0.0);
1340aTriangles->AddVertex ( 100./2., 100./2., 0.0);
7c42f3f4 1341aPrsGroup->AddPrimitiveArray (aTriangles);
1342aPrsGroup->SetGroupPrimitivesAspect (new Graphic3d_AspectFillArea3d());
72b7576f 1343
7c42f3f4 1344// Create Ambient and Infinite Lights in this Viewer
cfece3ef 1345Handle(V3d_AmbientLight) aLight1 = new V3d_AmbientLight (VM, Quantity_NOC_GRAY50);
1346Handle(V3d_DirectionalLight) aLight2 = new V3d_DirectionalLight (VM, V3d_XnegYnegZneg, Quantity_NOC_WHITE);
72b7576f 1347
4ee1bdf4 1348// Create a 3D quality Window with the same DisplayConnection
cfece3ef 1349Handle(Xw_Window) aWindow = new Xw_Window (aDispConnection, "Test V3d", 0.5, 0.5, 0.5, 0.5);
72b7576f 1350
cfece3ef 1351// Map this Window to this screen
72b7576f 1353
4ee1bdf4 1354// Create a Perspective View in this Viewer
cfece3ef 1355Handle(V3d_View) aView = new V3d_View (VM);
18006a0f 1356aView->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Perspective);
1357// Associate this View with the Window
cfece3ef 1358aView ->SetWindow (aWindow);
18006a0f 1359// Display ALL structures in this View
1361// Finally update the Visualization in this View
18006a0f 1363// Fit view to object size
72b7576f 1366
18006a0f 1367@subsubsection occt_visu_4_4_3 Define viewing parameters
72b7576f 1368
7c42f3f4 1369View projection and orientation in OCCT *V3d_View* are driven by camera. The camera calculates and supplies projection and view orientation matrices for rendering by OpenGL. The allows to the user to control all projection parameters. The camera is defined by the following properties:
72b7576f 1370
3f812249 1371* **Eye** -- defines the observer (camera) position. Make sure the Eye point never gets between the Front and Back clipping planes.
72b7576f 1372
3f812249 1373* **Center** -- defines the origin of View Reference Coordinates (where camera is aimed at).
72b7576f 1374
3f812249 1375* **Direction** -- defines the direction of camera view (from the Eye to the Center).
72b7576f 1376
3f812249 1377* **Distance** -- defines the distance between the Eye and the Center.
72b7576f 1378
3f812249 1379* **Front** Plane -- defines the position of the front clipping plane in View Reference Coordinates system.
72b7576f 1380
3f812249 1381* **Back** Plane -- defines the position of the back clipping plane in View Reference Coordinates system.
72b7576f 1382
3f812249 1383* **ZNear** -- defines the distance between the Eye and the Front plane.
72b7576f 1384
3f812249 1385* **ZFar** -- defines the distance between the Eye and the Back plane.
dba69de2 1386
18006a0f 1387Most common view manipulations (panning, zooming, rotation) are implemented as convenience methods of *V3d_View* class, however *Graphic3d_Camera* class can also be used directly by application developers:
72b7576f 1388
18006a0f 1389Example:
1391// rotate camera by X axis on 30.0 degrees
1392gp_Trsf aTrsf;
1393aTrsf.SetRotation (gp_Ax1 (gp_Pnt (0.0, 0.0, 0.0), gp_Dir (1.0, 0.0, 0.0)), 30.0);
1394aView->Camera()->Transform (aTrsf);
72b7576f 1396
18006a0f 1397@subsubsection occt_visu_4_4_4 Orthographic Projection
d6b4d3d0 1399@figure{view_frustum.png,"Perspective and orthographic projection",420}
72b7576f 1400
18006a0f 1401The following code configures the camera for orthographic rendering:
72b7576f 1402
bf62b306 1403~~~~~
18006a0f 1404// Create an orthographic View in this Viewer
1405Handle(V3d_View) aView = new V3d_View (VM);
1406aView->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Orthographic);
1407// update the Visualization in this View
72b7576f 1410
18006a0f 1411@subsubsection occt_visu_4_4_5 Perspective Projection
72b7576f 1412
3f812249 1413**Field of view (FOVy)** -- defines the field of camera view by y axis in degrees (45° is default).
72b7576f 1414
d6b4d3d0 1415@figure{camera_perspective.png,"Perspective frustum",420}
72b7576f 1416
18006a0f 1417The following code configures the camera for perspective rendering:
72b7576f 1418
bf62b306 1419~~~~~
18006a0f 1420// Create a perspective View in this Viewer
1421Handle(V3d_View) aView = new V3d_View(VM);
1422aView->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Perspective);
72b7576f 1425
72b7576f 1426
18006a0f 1427@subsubsection occt_visu_4_4_6 Stereographic Projection
72b7576f 1428
3f812249 1429**IOD** -- defines the intraocular distance (in world space units).
18006a0f 1430
1431There are two types of IOD:
7863dabb 1432* _Graphic3d_Camera::IODType_Absolute_ : Intraocular distance is defined as an absolute value.
1433* _Graphic3d_Camera::IODType_Relative_ : Intraocular distance is defined relative to the camera focal length (as its coefficient).
18006a0f 1434
3f812249 1435**Field of view (FOV)** -- defines the field of camera view by y axis in degrees (45° is default).
18006a0f 1436
3f812249 1437**ZFocus** -- defines the distance to the point of stereographic focus.
18006a0f 1438
d6b4d3d0 1439@figure{stereo.png,"Stereographic projection",420}
18006a0f 1440
1441To enable stereo projection, your workstation should meet the following requirements:
1443* The graphic card should support quad buffering.
1444* You need active 3D glasses (LCD shutter glasses).
1445* The graphic driver needs to be configured to impose quad buffering for newly created OpenGl contexts; the viewer and the view should be created after that.
1447In stereographic projection mode the camera prepares two projection matrices to display different stereo-pictures for the left and for the right eye. In a non-stereo camera this effect is not visible because only the same projection is used for both eyes.
7863dabb 1449To enable quad buffering support you should provide the following settings to the graphic driver *OpenGl_Caps*:
72b7576f 1450
18006a0f 1451~~~~~
1452Handle(OpenGl_GraphicDriver) aDriver = new OpenGl_GraphicDriver();
1453OpenGl_Caps& aCaps = aDriver->ChangeOptions();
1454aCaps.contextStereo = Standard_True;
bf62b306 1455~~~~~
72b7576f 1456
18006a0f 1457The following code configures the camera for stereographic rendering:
72b7576f 1458
18006a0f 1459~~~~~
1460// Create a Stereographic View in this Viewer
1461Handle(V3d_View) aView = new V3d_View(VM);
1462aView->Camera()->SetProjectionType (Graphic3d_Camera::Projection_Stereo);
1463// Change stereo parameters
1464aView->Camera()->SetIOD (IODType_Absolute, 5.0);
1465// Finally update the Visualization in this View
72b7576f 1468
18006a0f 1469@subsubsection occt_visu_4_4_7 View frustum culling
72b7576f 1470
18006a0f 1471The algorithm of frustum culling on CPU-side is activated by default for 3D viewer. This algorithm allows skipping the presentation outside camera at the rendering stage, providing better performance. The following features support this method:
1472* *Graphic3d_Structure::CalculateBoundBox()* is used to calculate axis-aligned bounding box of a presentation considering its transformation.
1473* *V3d_View::SetFrustumCulling* enables or disables frustum culling for the specified view.
7863dabb 1474* Classes *Graphic3d_BvhCStructureSet* and *Graphic3d_CullingTool* handle the detection of outer objects and usage of acceleration structure for frustum culling.
18006a0f 1475* *BVH_BinnedBuilder* class splits several objects with null bounding box.
72b7576f 1476
18006a0f 1477@subsubsection occt_visu_4_4_9 View background styles
7c42f3f4 1478There are three types of background styles available for *V3d_View*: solid color, gradient color and image.
72b7576f 1479
7c42f3f4 1480To set solid color for the background you can use the following method:
bf62b306 1481~~~~~
7c42f3f4 1482void V3d_View::SetBackgroundColor (const Quantity_Color& theColor);
bf62b306 1483~~~~~
72b7576f 1484
7c42f3f4 1485The gradient background style could be set up with the following method:
bf62b306 1486~~~~~
7c42f3f4 1487void V3d_View::SetBgGradientColors (const Quantity_Color& theColor1,
1488 const Quantity_Color& theColor2,
1489 const Aspect_GradientFillMethod theFillStyle,
1490 const Standard_Boolean theToUpdate = false);
bf62b306 1491~~~~~
72b7576f 1492
7c42f3f4 1493The *theColor1* and *theColor2* parameters define the boundary colors of interpolation, the *theFillStyle* parameter defines the direction of interpolation.
72b7576f 1494
7c42f3f4 1495To set the image as a background and change the background image style you can use the following method:
bf62b306 1496~~~~~
7c42f3f4 1497void V3d_View::SetBackgroundImage (const Standard_CString theFileName,
1498 const Aspect_FillMethod theFillStyle,
1499 const Standard_Boolean theToUpdate = false);
bf62b306 1500~~~~~
72b7576f 1501
7c42f3f4 1502The *theFileName* parameter defines the image file name and the path to it, the *theFillStyle* parameter defines the method of filling the background with the image. The methods are:
3f812249 1503 * *Aspect_FM_NONE* -- draws the image in the default position;
1504 * *Aspect_FM_CENTERED* -- draws the image at the center of the view;
1505 * *Aspect_FM_TILED* -- tiles the view with the image;
1506 * *Aspect_FM_STRETCH* -- stretches the image over the view.
72b7576f 1507
18006a0f 1508@subsubsection occt_visu_4_4_10 Dumping a 3D scene into an image file
72b7576f 1509
7c42f3f4 1510The 3D scene displayed in the view can be dumped into image file with resolution independent from window size (using offscreen buffer).
1511The *V3d_View* has the following methods for dumping the 3D scene:
4ee1bdf4 1512~~~~
7c42f3f4 1513Standard_Boolean V3d_View::Dump (const Standard_CString theFile,
1514 const Image_TypeOfImage theBufferType);
4ee1bdf4 1515~~~~
7c42f3f4 1516Dumps the scene into an image file with the view dimensions.
1517The raster image data handling algorithm is based on the *Image_AlienPixMap* class. The supported extensions are ".png", ".bmp", ".jpg" and others supported by **FreeImage** library.
7863dabb 1518The value passed as *theBufferType* argument defines the type of the buffer for an output image (RGB, RGBA, floating-point, RGBF, RGBAF). Method returns TRUE if the scene has been successfully dumped.
72b7576f 1519
4ee1bdf4 1520~~~~
7c42f3f4 1521Standard_Boolean V3d_View::ToPixMap (Image_PixMap& theImage,
1522 const V3d_ImageDumpOptions& theParams);
4ee1bdf4 1523~~~~
7c42f3f4 1524Dumps the displayed 3d scene into a pixmap with a width and height passed through parameters structure *theParams*.
72b7576f 1525
18006a0f 1526@subsubsection occt_visu_4_4_13 Ray tracing support
72b7576f 1527
18006a0f 1528OCCT visualization provides rendering by real-time ray tracing technique. It is allowed to switch easily between usual rasterization and ray tracing rendering modes. The core of OCCT ray tracing is written using GLSL shaders. The ray tracing has a wide list of features:
1529* Hard shadows
1530* Refractions
1531* Reflection
1532* Transparency
1533* Texturing
1534* Support of non-polygon objects, such as lines, text, highlighting, selection.
1535* Performance optimization using 2-level bounding volume hierarchy (BVH).
72b7576f 1536
18006a0f 1537The ray tracing algorithm is recursive (Whitted's algorithm). It uses BVH effective optimization structure. The structure prepares optimized data for a scene geometry for further displaying it in real-time. The time-consuming re-computation of the BVH is not necessary for view operations, selections, animation and even editing of the scene by transforming location of the objects. It is only necessary when the list of displayed objects or their geometry changes.
1538To make the BVH reusable it has been added into an individual reusable OCCT package *TKMath/BVH*.
1540There are several ray-tracing options that user can switch on/off:
1541* Maximum ray tracing depth
1542* Shadows rendering
1543* Specular reflections
1544* Adaptive anti aliasing
1545* Transparency shadow effects
1549Graphic3d_RenderingParams& aParams = aView->ChangeRenderingParams();
1550// specifies rendering mode
1551aParams.Method = Graphic3d_RM_RAYTRACING;
1552// maximum ray-tracing depth
1553aParams.RaytracingDepth = 3;
1554// enable shadows rendering
7c42f3f4 1555aParams.IsShadowEnabled = true;
18006a0f 1556// enable specular reflections.
7c42f3f4 1557aParams.IsReflectionEnabled = true;
18006a0f 1558// enable adaptive anti-aliasing
7c42f3f4 1559aParams.IsAntialiasingEnabled = true;
18006a0f 1560// enable light propagation through transparent media.
7c42f3f4 1561aParams.IsTransparentShadowEnabled = true;
18006a0f 1562// update the view
1566@subsubsection occt_visu_4_4_14 Display priorities
7c42f3f4 1568Structure display priorities control the order, in which structures are drawn. When you display a structure you specify its priority. The lower is the value, the lower is the display priority. When the display is regenerated, the structures with the lowest priority are drawn first. The structures with the same display priority are drawn in the same order as they have been displayed. OCCT supports eleven structure display priorities.
18006a0f 1569
1570@subsubsection occt_visu_4_4_15 Z-layer support
2683e647 1572OCCT features depth-arranging functionality called z-layer. A graphical presentation can be put into a z-layer. In general, this function can be used for implementing "bring to front" functionality in a graphical application.
18006a0f 1573
1577// set z-layer to an interactive object
7c42f3f4 1578Handle(AIS_InteractiveContext) theContext;
1579Handle(AIS_InteractiveObject) theInterObj;
18006a0f 1580Standard_Integer anId = 3;
1581aViewer->AddZLayer (anId);
7c42f3f4 1582theContext->SetZLayer (theInterObj, anId);
18006a0f 1583~~~~~
1585For each z-layer, it is allowed to:
1586* Enable / disable depth test for layer.
1587* Enable / disable depth write for layer.
1588* Enable / disable depth buffer clearing.
1589* Enable / disable polygon offset.
7c42f3f4 1591You can get the options using getter from *V3d_Viewer*. It returns *Graphic3d_ZLayerSettings* for a given *LayerId*.
18006a0f 1592
1595// change z-layer settings
1596Graphic3d_ZLayerSettings aSettings = aViewer->ZLayerSettings (anId);
7c42f3f4 1597aSettings.SetEnableDepthTest (true);
1599aSettings.SetClearDepth (true);
7c3ef2f7 1600aSettings.SetPolygonOffset (Graphic3d_PolygonOffset());
18006a0f 1601aViewer->SetZLayerSettings (anId, aSettings);
7c3ef2f7 1604Another application for Z-Layer feature is treating visual precision issues when displaying objects far from the World Center.
1605The key problem with such objects is that visualization data is stored and manipulated with single precision floating-point numbers (32-bit).
ebcbd824 1606Single precision 32-bit floating-point numbers give only 6-9 significant decimal digits precision,
1607while double precision 64-bit numbers give 15-17 significant decimal digits precision, which is sufficient enough for most applications.
7c3ef2f7 1608
ebcbd824 1609When moving an Object far from the World Center, float number steadily eats precision.
1610The camera Eye position adds leading decimal digits to the overall Object transformation, which discards smaller digits due to floating point number nature.
7c3ef2f7 1611For example, the object of size 0.0000123 moved to position 1000 has result transformation 1000.0000123,
1612which overflows single precision floating point - considering the most optimistic scenario of 9 significant digits (but it is really not this case), the result number will be 1000.00001.
ebcbd824 1614This imprecision results in visual artifacts of two kinds in the 3D Viewer:
7c3ef2f7 1615
1616* Overall per-vertex Object distortion.
ebcbd824 1617 This happens when each vertex position has been defined within World Coordinate system.
1618* The object itself is not distorted, but its position in the World is unstable and imprecise - the object jumps during camera manipulations.
7c3ef2f7 1619 This happens when vertices have been defined within Local Coordinate system at the distance small enough to keep precision within single precision float,
1620 however Local Transformation applied to the Object is corrupted due to single precision float.
ebcbd824 1622The first issue cannot be handled without switching the entire presentation into double precision (for each vertex position).
7c3ef2f7 1623However, visualization hardware is much faster using single precision float number rather than double precision - so this is not an option in most cases.
1624The second issue, however, can be negated by applying special rendering tricks.
7c42f3f4 1626So, to apply this feature in OCCT, the application:
7c3ef2f7 1627
ebcbd824 1628* Defines Local Transformation for each object to fit the presentation data into single precision float without distortion.
1629* Spatially splits the world into smaller areas/cells where single precision float will be sufficient.
7c3ef2f7 1630 The size of such cell might vary and depends on the precision required by application (e.g. how much user is able to zoom in camera within application).
ebcbd824 1631* Defines a Z-Layer for each spatial cell containing any object.
1632* Defines the Local Origin property of the Z-Layer according to the center of the cell.
7c42f3f4 1633
1635Graphic3d_ZLayerSettings aSettings = aViewer->ZLayerSettings (anId);
1636aSettings.SetLocalOrigin (400.0, 0.0, 0.0);
ebcbd824 1638* Assigns a presentable object to the nearest Z-Layer.
7c3ef2f7 1639
ebcbd824 1640Note that Local Origin of the Layer is used only for rendering - everything outside will be still defined in the World Coordinate System,
7c3ef2f7 1641including Local Transformation of the Object and Detection results.
ebcbd824 1642E.g., while moving the presentation between Z-layers with different Local Origins, the Object will stay at the same place - only visualization quality will vary.
18006a0f 1643
1644@subsubsection occt_visu_4_4_16 Clipping planes
1646The ability to define custom clipping planes could be very useful for some tasks. OCCT provides such an opportunity.
1648The *Graphic3d_ClipPlane* class provides the services for clipping planes: it holds the plane equation coefficients and provides its graphical representation. To set and get plane equation coefficients you can use the following methods:
7c42f3f4 1651Graphic3d_ClipPlane::Graphic3d_ClipPlane (const gp_Pln& thePlane)
18006a0f 1652void Graphic3d_ClipPlane::SetEquation (const gp_Pln& thePlane)
7c42f3f4 1653Graphic3d_ClipPlane::Graphic3d_ClipPlane (const Equation& theEquation)
18006a0f 1654void Graphic3d_ClipPlane::SetEquation (const Equation& theEquation)
1655gp_Pln Graphic3d_ClipPlane::ToPlane() const
1658The clipping planes can be activated with the following method:
1660void Graphic3d_ClipPlane::SetOn (const Standard_Boolean theIsOn)
7c42f3f4 1663The number of clipping planes is limited. You can check the limit value via method *Graphic3d_GraphicDriver::InquireLimit()*;
18006a0f 1664
1666// get the limit of clipping planes for the current view
7c42f3f4 1667Standard_Integer aMaxClipPlanes = aView->Viewer()->Driver()->InquireLimit (Graphic3d_TypeOfLimit_MaxNbClipPlanes);
18006a0f 1668~~~~~
1670Let us see for example how to create a new clipping plane with custom parameters and add it to a view or to an object:
1672// create a new clipping plane
1673const Handle(Graphic3d_ClipPlane)& aClipPlane = new Graphic3d_ClipPlane();
1674// change equation of the clipping plane
2683e647 1675Standard_Real aCoeffA = ...
1676Standard_Real aCoeffB = ...
1677Standard_Real aCoeffC = ...
1678Standard_Real aCoeffD = ...
18006a0f 1679aClipPlane->SetEquation (gp_Pln (aCoeffA, aCoeffB, aCoeffC, aCoeffD));
1680// set capping
1681aClipPlane->SetCapping (aCappingArg == "on");
1682// set the material with red color of clipping plane
1683Graphic3d_MaterialAspect aMat = aClipPlane->CappingMaterial();
1684Quantity_Color aColor (1.0, 0.0, 0.0, Quantity_TOC_RGB);
1685aMat.SetAmbientColor (aColor);
1686aMat.SetDiffuseColor (aColor);
1687aClipPlane->SetCappingMaterial (aMat);
1688// set the texture of clipping plane
2683e647 1689Handle(Graphic3d_Texture2Dmanual) aTexture = ...
18006a0f 1690aTexture->EnableModulate();
1692aClipPlane->SetCappingTexture (aTexture);
1693// add the clipping plane to an interactive object
2683e647 1694Handle(AIS_InteractiveObject) aIObj = ...
18006a0f 1695aIObj->AddClipPlane (aClipPlane);
1696// or to the whole view
1697aView->AddClipPlane (aClipPlane);
1698// activate the clipping plane
1700// update the view
1705@subsubsection occt_visu_4_4_17 Automatic back face culling
1707Back face culling reduces the rendered number of triangles (which improves the performance) and eliminates artifacts at shape boundaries. However, this option can be used only for solid objects, where the interior is actually invisible from any point of view. Automatic back-face culling mechanism is turned on by default, which is controlled by *V3d_View::SetBackFacingModel()*.
7863dabb 1709The following features are applied in *StdPrs_ToolTriangulatedShape::IsClosed()*, which is used for definition of back face culling in *ShadingAspect*:
18006a0f 1710* disable culling for free closed Shells (not inside the Solid) since reversed orientation of a free Shell is a valid case;
1711* enable culling for Solids packed into a compound;
1712* ignore Solids with incomplete triangulation.
1714Back face culling is turned off at TKOpenGl level in the following cases:
1715* clipping/capping planes are in effect;
1716* for translucent objects;
1717* with hatching presentation style.
1719@subsection occt_visu_4_5 Examples: creating a 3D scene
7c42f3f4 1721To create 3D graphic objects and display them in the screen, follow the procedure below:
18006a0f 17221. Create attributes.
17232. Create a 3D viewer.
17243. Create a view.
17254. Create an interactive context.
17265. Create interactive objects.
7c42f3f4 17276. Create primitives in the interactive object.
18006a0f 17287. Display the interactive object.
1730@subsubsection occt_visu_4_5_1 Create attributes
1732Create colors.
1735Quantity_Color aBlack (Quantity_NOC_BLACK);
1736Quantity_Color aBlue (Quantity_NOC_MATRABLUE);
1737Quantity_Color aBrown (Quantity_NOC_BROWN4);
1738Quantity_Color aFirebrick (Quantity_NOC_FIREBRICK);
1739Quantity_Color aForest (Quantity_NOC_FORESTGREEN);
1740Quantity_Color aGray (Quantity_NOC_GRAY70);
1741Quantity_Color aMyColor (0.99, 0.65, 0.31, Quantity_TOC_RGB);
1742Quantity_Color aBeet (Quantity_NOC_BEET);
1743Quantity_Color aWhite (Quantity_NOC_WHITE);
1746Create line attributes.
1749Handle(Graphic3d_AspectLine3d) anAspectBrown = new Graphic3d_AspectLine3d();
1750Handle(Graphic3d_AspectLine3d) anAspectBlue = new Graphic3d_AspectLine3d();
1751Handle(Graphic3d_AspectLine3d) anAspectWhite = new Graphic3d_AspectLine3d();
1752anAspectBrown->SetColor (aBrown);
1753anAspectBlue ->SetColor (aBlue);
1754anAspectWhite->SetColor (aWhite);
1757Create marker attributes.
1759Handle(Graphic3d_AspectMarker3d aFirebrickMarker = new Graphic3d_AspectMarker3d();
1760// marker attributes
1761aFirebrickMarker->SetColor (Firebrick);
1762aFirebrickMarker->SetScale (1.0);
1763aFirebrickMarker->SetType (Aspect_TOM_BALL);
1764// or this
1765// it is a preferred way (supports full-color images on modern hardware).
1766aFirebrickMarker->SetMarkerImage (theImage)
1769Create facet attributes.
1771Handle(Graphic3d_AspectFillArea3d) aFaceAspect = new Graphic3d_AspectFillArea3d();
1772Graphic3d_MaterialAspect aBrassMaterial (Graphic3d_NOM_BRASS);
1773Graphic3d_MaterialAspect aGoldMaterial (Graphic3d_NOM_GOLD);
2a332745 1774aFaceAspect->SetInteriorStyle (Aspect_IS_SOLID_WIREFRAME);
18006a0f 1775aFaceAspect->SetInteriorColor (aMyColor);
1776aFaceAspect->SetDistinguishOn ();
1777aFaceAspect->SetFrontMaterial (aGoldMaterial);
1778aFaceAspect->SetBackMaterial (aBrassMaterial);
18006a0f 1779~~~~~
1781Create text attributes.
1783Handle(Graphic3d_AspectText3d) aTextAspect = new Graphic3d_AspectText3d (aForest, Graphic3d_NOF_ASCII_MONO, 1.0, 0.0);
1786@subsubsection occt_visu_4_5_2 Create a 3D Viewer (a Windows example)
1789// create a default connection
1790Handle(Aspect_DisplayConnection) aDisplayConnection;
1791// create a graphic driver from default connection
7c42f3f4 1792Handle(OpenGl_GraphicDriver) aGraphicDriver = new OpenGl_GraphicDriver (aDisplayConnection);
18006a0f 1793// create a viewer
7c42f3f4 1794myViewer = new V3d_Viewer (aGraphicDriver);
18006a0f 1795// set parameters for V3d_Viewer
1796// defines default lights -
1797// positional-light 0.3 0.0 0.0
1798// directional-light V3d_XnegYposZpos
1799// directional-light V3d_XnegYneg
1800// ambient-light
1802// activates all the lights defined in this viewer
1804// set background color to black
1805a3DViewer->SetDefaultBackgroundColor (Quantity_NOC_BLACK);
1809@subsubsection occt_visu_4_5_3 Create a 3D view (a Windows example)
7c42f3f4 1811It is assumed that a valid Windows window may already be accessed via the method *GetSafeHwnd()* (as in case of MFC sample).
18006a0f 1812~~~~~
7c42f3f4 1813Handle(WNT_Window) aWNTWindow = new WNT_Window (GetSafeHwnd());
18006a0f 1814myView = myViewer->CreateView();
1815myView->SetWindow (aWNTWindow);
1818@subsubsection occt_visu_4_5_4 Create an interactive context
1821myAISContext = new AIS_InteractiveContext (myViewer);
1824You are now able to display interactive objects such as an *AIS_Shape*.
1827TopoDS_Shape aShape = BRepAPI_MakeBox (10, 20, 30).Solid();
7c42f3f4 1828Handle(AIS_Shape) anAISShape = new AIS_Shape (aShape);
18006a0f 1829myAISContext->Display (anAISShape);
2683e647 1832@subsubsection occt_visu_4_5_5 Create your own interactive object
18006a0f 1833
1834Follow the procedure below to compute the presentable object:
67d7f07f 18361. Build a presentable object inheriting from *AIS_InteractiveObject* (refer to the Chapter on @ref occt_visu_2_1 "Presentable Objects").
7863dabb 18372. Reuse the *Graphic3d_Structure* provided as an argument of the compute methods.
18006a0f 1838
1839**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.
18006a0f 1841Let us look at the example of compute methods
7c42f3f4 1844void MyPresentableObject::Compute (const Handle(PrsMgr_PresentationManager3d)& thePrsManager,
7863dabb 1845 const Handle(Graphic3d_Structure)& thePrs,
7c42f3f4 1846 const Standard_Integer theMode)
18006a0f 1847(
1848 //...
7c42f3f4 1851void MyPresentableObject::Compute (const Handle(Prs3d_Projector)& theProjector,
7863dabb 1852 const Handle(Graphic3d_Structure)& thePrs)
18006a0f 1853(
1854 //...
1858@subsubsection occt_visu_4_5_6 Create primitives in the interactive object
7863dabb 1860Get the group used in *Graphic3d_Structure*.
18006a0f 1861
7c42f3f4 1863Handle(Graphic3d_Group) aGroup = thePrs->NewGroup();
18006a0f 1864~~~~~
1866Update the group attributes.
7c42f3f4 1869aGroup->SetGroupPrimitivesAspect (anAspectBlue);
18006a0f 1870~~~~~
1872Create two triangles in *aGroup*.
1875Standard_Integer aNbTria = 2;
7c42f3f4 1876Handle(Graphic3d_ArrayOfTriangles) aTriangles = new Graphic3d_ArrayOfTriangles (3 * aNbTria, 0, true);
1877for (Standard_Integer aTriIter = 1; aTriIter <= aNbTria; ++aTriIter)
18006a0f 1878{
7c42f3f4 1879 aTriangles->AddVertex (aTriIter * 5., 0., 0., 1., 1., 1.);
1880 aTriangles->AddVertex (aTriIter * 5 + 5, 0., 0., 1., 1., 1.);
1881 aTriangles->AddVertex (aTriIter * 5 + 2.5, 5., 0., 1., 1., 1.);
18006a0f 1882}
18006a0f 1883aGroup->AddPrimitiveArray (aTriangles);
7c42f3f4 1884aGroup->SetGroupPrimitivesAspect (new Graphic3d_AspectFillArea3d());
18006a0f 1885~~~~~
18006a0f 1887Use the polyline function to create a boundary box for the *thePrs* structure in group *aGroup*.
1890Standard_Real Xm, Ym, Zm, XM, YM, ZM;
1891thePrs->MinMaxValues (Xm, Ym, Zm, XM, YM, ZM);
1893Handle(Graphic3d_ArrayOfPolylines) aPolylines = new Graphic3d_ArrayOfPolylines (16, 4);
1894aPolylines->AddBound (4);
1895aPolylines->AddVertex (Xm, Ym, Zm);
1896aPolylines->AddVertex (Xm, Ym, ZM);
1897aPolylines->AddVertex (Xm, YM, ZM);
1898aPolylines->AddVertex (Xm, YM, Zm);
1899aPolylines->AddBound (4);
1900aPolylines->AddVertex (Xm, Ym, Zm);
1901aPolylines->AddVertex (XM, Ym, Zm);
1902aPolylines->AddVertex (XM, Ym, ZM);
1903aPolylines->AddVertex (XM, YM, ZM);
1904aPolylines->AddBound (4);
1905aPolylines->AddVertex (XM, YM, Zm);
1906aPolylines->AddVertex (XM, Ym, Zm);
1907aPolylines->AddVertex (XM, YM, Zm);
1908aPolylines->AddVertex (Xm, YM, Zm);
1909aPolylines->AddBound (4);
1910aPolylines->AddVertex (Xm, YM, ZM);
1911aPolylines->AddVertex (XM, YM, ZM);
1912aPolylines->AddVertex (XM, Ym, ZM);
1913aPolylines->AddVertex (Xm, Ym, ZM);
18006a0f 1915aGroup->AddPrimitiveArray(aPolylines);
7c42f3f4 1916aGroup->SetGroupPrimitivesAspect (new Graphic3d_AspectLine3d());
18006a0f 1917~~~~~
1919Create text and markers in group *aGroup*.
1922static char* texte[3] =
1924 "Application title",
1925 "My company",
1926 "My company address."
1928Handle(Graphic3d_ArrayOfPoints) aPtsArr = new Graphic3d_ArrayOfPoints (2, 1);
1929aPtsArr->AddVertex (-40.0, -40.0, -40.0);
1930aPtsArr->AddVertex (40.0, 40.0, 40.0);
18006a0f 1931aGroup->AddPrimitiveArray (aPtsArr);
7c42f3f4 1932aGroup->SetGroupPrimitivesAspect (new Graphic3d_AspectText3d());
18006a0f 1933
1934Graphic3d_Vertex aMarker (0.0, 0.0, 0.0);
7c42f3f4 1935for (int i = 0; i <= 2; i++)
18006a0f 1936{
1937 aMarker.SetCoord (-(Standard_Real )i * 4 + 30,
1938 (Standard_Real )i * 4,
1939 -(Standard_Real )i * 4);
1940 aGroup->Text (texte[i], Marker, 20.);
1945@section occt_visu_5 Mesh Visualization Services
7c42f3f4 1947*MeshVS* (Mesh Visualization Service) component extends 3D visualization capabilities of Open CASCADE Technology. It provides flexible means of displaying meshes along with associated pre- and post-processor data.
18006a0f 1948
1949From a developer's point of view, it is easy to integrate the *MeshVS* component into any mesh-related application with the following guidelines:
1951* Derive a data source class from the *MeshVS_DataSource* class.
7c42f3f4 1952* Re-implement its virtual methods, so as to give the *MeshVS* component access to the application data model. This is the most important part of the job, since visualization performance is affected by performance of data retrieval methods of your data source class.
1953* Create an instance of *MeshVS_Mesh* class.
1954* Create an instance of your data source class and pass it to a *MeshVS_Mesh* object through the *SetDataSource()* method.
1955* Create one or several objects of *MeshVS_PrsBuilder*-derived classes (standard, included in the *MeshVS* package, or your custom ones).
1956* Each *PrsBuilder* is responsible for drawing a *MeshVS_Mesh* presentation in a certain display mode(s) specified as a *PrsBuilder* constructor's argument. Display mode is treated by *MeshVS* classes as a combination of bit flags (two least significant bits are used to encode standard display modes: wireframe, shading and shrink).
1957* Pass these objects to the *MeshVS_Mesh::AddBuilder()* method. *MeshVS_Mesh* takes advantage of improved selection highlighting mechanism: it highlights its selected entities itself, with the help of so called "highlighter" object. You can set one of *PrsBuilder* objects to act as a highlighter with the help of a corresponding argument of the *AddBuilder()* method.
72b7576f 1958
7c42f3f4 1959Visual attributes of the *MeshVS_Mesh* object (such as shading color, shrink coefficient and so on) are controlled through *MeshVS_Drawer* object. It maintains a map "Attribute ID --> attribute value" and can be easily extended with any number of custom attributes.
d6b4d3d0 1960
7c42f3f4 1961In all other respects, *MeshVS_Mesh* is very similar to any other class derived from *AIS_InteractiveObject* and it should be used accordingly (refer to the description of *AIS package* in the documentation).