OpenGL color tracking and Open Cascade

I'm going to develop a FEM postprocessor with OCC.

In FEM postprocessing, it is very important to assign respective color to each node(or vertex), but I can not find a method to do that.

I know that in Graphic3d_group I can assign each color to each vertex, but in that case I can not shade that triangle.

In OpenGL there is a way to do that easily. that is to use GL_COLOR_MATERIAL switch, which enalbles color tracking capability which forces the vertex material color to be the color assigned to that vertex automatically.

I tested it with exoTK. and here is my modification to test.

The following code displays a mesh with random color at each vertex. but it is never shaded at all. If I use material properties, then the color values don't work, and all mesh is shaded with the one color of the material.

Is there a method to do that in OCC?

void exotkAIS_StdPrs::DisplayShading(const Handle_exotkMesh_Mesh& aMesh,const Handle_Prs3d_Presentation& aPresentation,const Handle_AIS_Drawer& aDrawer)
{
if ( aMesh.IsNull() || (aMesh->NbSubMeshes() == 0) )
return;

exotkGUI::ShowWaitCursor();
Handle_Graphic3d_Structure theStructure = Handle_Graphic3d_Structure::DownCast(aPresentation);
Handle_Graphic3d_Group theGroup= new Graphic3d_Group(theStructure);

Handle(Graphic3d_AspectFillArea3d) AsptArea = new Graphic3d_AspectFillArea3d();
AsptArea->SetInteriorStyle(Aspect_IS_SOLID);
Graphic3d_MaterialAspect mat = AsptArea->FrontMaterial();
mat.SetReflectionModeOff(Graphic3d_TOR_AMBIENT);
mat.SetReflectionModeOff(Graphic3d_TOR_DIFFUSE);
mat.SetReflectionModeOff(Graphic3d_TOR_SPECULAR);
mat.SetReflectionModeOff(Graphic3d_TOR_EMISSION);
AsptArea->SetFrontMaterial(mat);

theGroup->SetPrimitivesAspect(AsptArea);

theGroup->BeginPrimitives();

exotkMesh_ListIteratorOfListOfSubMesh theSubMeshIter;
exotkMesh_ListOfSubMesh theSubMeshes;
aMesh->SubMeshes(theSubMeshes);
exotkMesh_IndexedMapOfVertex theVertices;
exotkMesh_MapOfTriangle theTriangles;
exotkMesh_MapIteratorOfMapOfTriangle theMapIter;
Standard_Integer i1,i2,i3;
for ( theSubMeshIter.Initialize(theSubMeshes) ; theSubMeshIter.More() ; theSubMeshIter.Next() )
{
Handle_exotkMesh_SubMesh theCurrentSubMesh = theSubMeshIter.Value();
if ( !theCurrentSubMesh.IsNull() )
{
theCurrentSubMesh->Vertices(theVertices);
theCurrentSubMesh->Triangles(theTriangles);

for ( theMapIter.Initialize(theTriangles) ; theMapIter.More() ; theMapIter.Next() )
{
Handle_exotkMesh_Triangle theTriangle = theMapIter.Key();
theTriangle->Components(i1,i2,i3);
gp_Pnt P1 = theVertices.FindKey(i1)->Point();
gp_Pnt P2 = theVertices.FindKey(i2)->Point();
gp_Pnt P3 = theVertices.FindKey(i3)->Point();
gp_Vec V1 = theVertices.FindKey(i1)->Normal();
gp_Vec V2 = theVertices.FindKey(i2)->Normal();
gp_Vec V3 = theVertices.FindKey(i3)->Normal();

Aspect_Array1OfEdge aListEdge(1, 3 );
aListEdge.SetValue(1,Aspect_Edge(1,2,Aspect_TOE_VISIBLE));
aListEdge.SetValue(2,Aspect_Edge(2,3,Aspect_TOE_VISIBLE));
aListEdge.SetValue(3,Aspect_Edge(3,1,Aspect_TOE_VISIBLE));

Graphic3d_Array1OfVertexNC theArray1(1,3);
Quantity_Color color1,color2,color3;

color1 = exotkUtils::RandomColor();
theArray1.SetValue(1,Graphic3d_VertexNC(P1.X(),P1.Y(),P1.Z(),V1.X(),V1.Y(),V1.Z(),color1));
color2 = exotkUtils::RandomColor();
theArray1.SetValue(2,Graphic3d_VertexNC(P2.X(),P2.Y(),P2.Z(),V2.X(),V2.Y(),V2.Z(),color2));
color3 = exotkUtils::RandomColor();
theArray1.SetValue(3,Graphic3d_VertexNC(P3.X(),P3.Y(),P3.Z(),V3.X(),V3.Y(),V3.Z(),color3));

theGroup->TriangleSet(theArray1,aListEdge);

}
}
}
theGroup->EndPrimitives();

DisplayBoundaryBox(aPresentation,aDrawer);

exotkGUI::HideWaitCursor();

}