To visualize an OCCT topological shape in VTK viewer, it is necessary to perform the following steps:
1. Create *IVtkOCC_Shape* instance (VIS wrapper for OCCT shape) and initialize it with *TopoDS_Shape* object containing the actual geometry:
-~~~~
+~~~~{.cpp}
TopoDS_Shape aShape;
// Initialize aShape variable: e.g. load it from BREP file
IVtkOCC_Shape::Handle aShapeImpl = new IVtkOCC_Shape(aShape);
~~~~
2. Create VTK polygonal data source for the target OCCT topological shape and initialize it with created *IVtkOCC_Shape* instance. At this stage the faceter is implicitly plugged:
-~~~~
+~~~~{.cpp}
vtkSmartPointer<IVtkTools_ShapeDataSource> DS = vtkSmartPointer<IVtkTools_ShapeDataSource>::New();
DS->SetShape(aShapeImpl);
~~~~
3. Visualize the loaded shape in usual VTK way starting a pipeline from the newly created specific source:
-~~~~
+~~~~{.cpp}
vtkSmartPointer<vtkPolyDataMapper> Mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
Mapper->SetInputConnection(aDS->GetOutputPort());
~~~~
It is always possible to access the shape data source from VTK actor by means of dedicated methods from *IVtkTools_ShapeObject* class:
-~~~~
+~~~~{.cpp}
IVtkTools_ShapeDataSource* DS = IVtkTools_ShapeObject::GetShapeSource(Actor);
IVtkOCC_Shape::Handle occShape = IVtkTools_ShapeObject::GetOccShape(Actor);
~~~~
It is also possible to get a shape wrapper from the shape data source:
-~~~~
+~~~~{.cpp}
IVtkOCC_Shape::Handle occShape = DS->GetShape();
~~~~
To colorize different parts of a shape according to the default OCCT color scheme, it is possible to configure the corresponding VTK mapper using a dedicated auxiliary function of *IVtkTools* namespace:
-~~~~
+~~~~{.cpp}
IVtkTools::InitShapeMapper(Mapper);
~~~~
It is possible to get an instance of *vtkLookupTable class* with a default OCCT color scheme by means of the following method:
-~~~~
+~~~~{.cpp}
vtkSmartPointer<vtkLookupTable> Table = IVtkTools::InitLookupTable();
~~~~
@subsubsection occt_vis_3_2_2 Custom color scheme
To set up application-specific colors for a shape presentation, use *InitShapeMapper* function with an additional argument passing a custom lookup table:
-~~~~
+~~~~{.cpp}
IVtkTools::InitShapeMapper(Mapper, Table);
~~~~
@subsubsection occt_vis_3_2_3 Setting custom colors for sub-shapes
It is also possible to bind custom colors to any sub-shape type listed in *IVtk_MeshType* enumeration. For example, to access the color bound to *free edge* entities, the following calls are available in *IVtkTools* namespace:
-~~~~
+~~~~{.cpp}
SetLookupTableColor(aLookupTable, MT_FreeEdge, R, G, B);
SetLookupTableColor(aLookupTable, MT_FreeEdge, R, G, B, A);
GetLookupTableColor(aLookupTable, MT_FreeEdge, R, G, B);
As VTK color mapping approach is based on associating scalar data arrays to VTK cells, the coloring of shape components can be turned on/off in the following way:
-~~~~
+~~~~{.cpp}
Mapper->ScalarVisibilityOn(); // use colors from lookup table
Mapper->ScalarVisibilityOff(); // use a color of actor’s property
~~~~
For example, the shading representation can be obtained in the following way:
-~~~~
+~~~~{.cpp}
vtkSmartPointer<IVtkTools_ShapeDataSource> DS = vtkSmartPointer<IVtkTools_ShapeDataSource>::New();
vtkSmartPointer<IVtkTools_DisplayModeFilter> DMFilter = vtkSmartPointer<IVtkTools_DisplayModeFilter>::New();
@subsection occt_vis_3_4 Interactive selection
*IVtkTools* package provides *IVtkTools_ShapePicker* class to perform selection of OCCT shapes and sub-shapes in VTK viewer and access the picking results. The typical usage of *IVtkTools_ShapePicker* tool consists in the following sequence of actions:
1. Create a picker and set its renderer to your active VTK renderer:
-~~~~
+~~~~{.cpp}
vtkSmartPointer<IVtkTools_ShapePicker> aPicker = vtkSmartPointer<IVtkTools_ShapePicker>::New();
aPicker->SetRenderer(aRenderer);
~~~~
2. Activate the desired selection mode by choosing the corresponding sub-shape types from *IVtk_SelectionMode* enumeration. For example, the following call allows selection of edges on all selectable shape actors of the renderer:
-~~~~
+~~~~{.cpp}
aPicker->SetSelectionMode(SM_Edge);
~~~~
If it is necessary to limit selection by a particular shape actor, one can use the mentioned *SetSelectionMode* method with *IVtk_IShape* handle or *vtkActor* pointer as the first argument:
-~~~~
+~~~~{.cpp}
IVtk_IShape::Handle aShape = new IVtkOCC_Shape(occShape);
aPicker->SetSelectionMode(aShape, SM_Edge); // If shape handle is available
aPicker->SetSelectionMode(anActor, SM_Edge); // If shape actor is available
~~~~
Different selection modes can be turned on/off for a picker at the same time independently from each other.
-~~~~
+~~~~{.cpp}
aPicker->SetSelectionMode(SM_Edge);
aPicker->SetSelectionMode(SM_Face);
~~~~
To turn off a selection mode, the additional optional Boolean parameter is used with *false* value, for example:
-~~~~
+~~~~{.cpp}
aPicker->SetSelectionMode(aShape, SM_Edge, false);
~~~~
3. Call *Pick* method passing the mouse display coordinates:
-~~~~
+~~~~{.cpp}
aPicker->Pick(x, y, 0);
~~~~
By default, the renderer passed in the step 1 is used. In order to perform pick operation for another renderer an additional optional parameter can be specified:
-~~~~
+~~~~{.cpp}
aPicker->Pick(x, y, 0, aRenderer);
~~~~
4. Obtain the top-level picking results as a collection of picked VTK actors:
-~~~~
+~~~~{.cpp}
vtkActorCollection* anActorCollection = aPicker->GetPickedActors();
~~~~
or as a collection of picked shape IDs:
-~~~~
+~~~~{.cpp}
IVtk_ShapeIdList ids = aPicker->GetPickedShapesIds();
~~~~
These methods return a single top picked actor or a shape by default. To get all the picked actors or shapes it is necessary to send “true” value in the optional Boolean parameter:
-~~~~
+~~~~{.cpp}
anActorCollection = aPicker->GetPickedActors(true);
ids = aPicker->GetPickedShapesIds(true);
~~~~
5. Obtain the picked sub-shape IDs:
-~~~~
+~~~~{.cpp}
IVtk_ShapeIdList subShapeIds = aPicker->GetPickedSubShapesIds(shapeId);
~~~~
This method also returns a single ID of a top-level picked sub-shape and has the same optional Boolean parameter to get all the picked sub-shapes of a shape:
-~~~~
+~~~~{.cpp}
subShapeIds = aPicker->GetPickedSubShapesIds(shapeId, true);
~~~~
For example, sub-shapes can be represented in VTK viewer in the following way:
-~~~~
+~~~~{.cpp}
// Load a shape into data source (see 3.1)
...
vtkSmartPointer<IVtkTools_ShapeDataSource> DS = vtkSmartPointer<IVtkTools_ShapeDataSource>::New();
The visualization pipeline for OCCT shape presentation can be initialized as follows:
1. Create an instance of *IShape* class initialized by OCCT topological shape:
-~~~~
+~~~~{.cpp}
TopoDS_Shape aShape;
// Load or create a TopoDS_Shape in the variable a Shape
IVtkOCC_Shape::Handle aShapeImpl = new IVtkOCC_Shape(aShape);
~~~~
2. Create an empty instance of IShapeData implementation for VTK:
-~~~~
+~~~~{.cpp}
IVtk_IShapeData::Handle aDataImpl = new IVtkVTK_ShapeData();
~~~~
3 Create an instance of *IShapeMesher* implementation for OCCT (any faceter can be used at this stage):
-~~~~
+~~~~{.cpp}
IVtk_IShapeMesher::Handle aMesher = new IVtkOCC_ShapeMesher();
~~~~
4 Triangulate the OCCT topological shape by means of the Mesher and access the result:
-~~~~
+~~~~{.cpp}
aMesher->Build (aShapeImpl, aDataImpl);
vtkPolyData* aPolyData = aDataImpl->GetVtkPolyData();
The typical usage of *IVtk_IShapePickerAlgo* consists in the following sequence of actions:
1. Create an instance of the picker class:
-~~~~
+~~~~{.cpp}
IVtkOCC_ShapePickerAlgo::Handle Picker = new IVtkOCC_ShapePickerAlgo();
~~~~
2. Set an instance of *IVtk_IView* class to the algorithm in order to define the viewer parameters:
-~~~~
+~~~~{.cpp}
IVtkVTK_View::Handle View = new IVtkVTK_View(Renderer);
Picker->SetView(View);
~~~~
3. Activate the desired selection modes using values from *IVtk_SelectionMode* enumeration. For example, the following call allows selection of edges:
-~~~~
+~~~~{.cpp}
TopoDS_Shape aShape;
// Load or create a TopoDS_Shape in the variable a Shape
...
~~~~
Different selection modes can be turned on/off for a picker at the same time independently from each other.
To turn off a selection mode the additional optional Boolean parameter is used with *false* value, for example:
-~~~~
+~~~~{.cpp}
myOccPickerAlgo->SetSelectionMode(occShape, SM_Edge, false);
~~~~
4. Call *Pick* method passing the mouse coordinates:
-~~~~
+~~~~{.cpp}
myOccPickerAlgo->Pick(x, y);
~~~~
5. Obtain top-level picking results as IDs of the picked top-level shapes:
-~~~~
+~~~~{.cpp}
IVtk_ShapeIdList ids = myOccPickerAlgo->ShapesPicked();
~~~~
6. Obtain IDs of the picked sub-shapes:
-~~~~
+~~~~{.cpp}
IVtk_ShapeIdList subShapeIds
= myOccPickerAlgo->SubShapesPicked(shapeId);
~~~~
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