Setting colors in TopoDS_Face is not resolved by FreeCAD or SolidWork

[frankpian]

Use XCAFDoc_ColorTool to set the color of a TopoDS_Face, ,then save it as a STEP file.

Handle(TDocStd_Document) hDoc;
    Quantity_Color redColor(Quantity_NOC_RED);
    XCAFApp_Application::GetApplication()->NewDocument("MDTV-XCAF", hDoc);

    Handle(XCAFDoc_ColorTool) hColorTool = XCAFDoc_DocumentTool::ColorTool(hDoc->Main());
    Handle(XCAFDoc_ShapeTool) hShapeTool = XCAFDoc_DocumentTool::ShapeTool(hDoc->Main());

    gp_Circ aCirc(gp_Ax2(gp_Pnt(0, 0, 0), gp_Dir(0, 0, 1)), 100);
    BRepBuilderAPI_MakeWire wire;
    TopoDS_Edge aEdge = BRepBuilderAPI_MakeEdge(aCirc);
    wire.Add(aEdge);
    BRepBuilderAPI_MakeFace face(wire.Wire());

    TDF_Label aLabel = hShapeTool->NewShape();
    TDataStd_Name::Set(aLabel, "testModel");
    TDF_Label newLabel = hShapeTool->AddComponent(aLabel, face.Face());
    hColorTool->SetColor(newLabel, redColor, XCAFDoc_ColorSurf);
    hColorTool->SetColor(newLabel, redColor, XCAFDoc_ColorGen);
    hColorTool->SetColor(newLabel, redColor, XCAFDoc_ColorCurv);
    hShapeTool->UpdateAssemblies();

    STEPCAFControl_Writer aWriter;
    aWriter.SetColorMode(Standard_True);
    if (aWriter.Transfer(hDoc, STEPControl_AsIs) != IFSelect_RetDone)
    {
        std::cerr << "Failed to transfer document" << std::endl;
        return 0;
    }

    if (aWriter.Write("myColoredFace.stp") != IFSelect_RetDone)
    {
        std::cerr << "Failed to write STEP file" << std::endl;
        return 0;
    }

Viewing with CAD assistant is normal.



Freecad and Solidwork don't show colors.

 

[calciffer]

Hi, @frankpian

 

[frankpian]

Hi, @frankpian

View attachment 792

Thanks for the reply.
I followed the settings in the picture, but it still didn't work. When the color is set to solid, FreeCAD can display normally, but it can't when it's set to face. I'm confused, is this a bug?

 

[calciffer]

hColorTool->SetColor(newLabel, redColor, XCAFDoc_ColorSurf);
hColorTool->SetColor(newLabel, redColor, XCAFDoc_ColorGen);
hColorTool->SetColor(newLabel, redColor, XCAFDoc_ColorCurv);

This might be the issue

 

[Quaoar]

@frankpian

A subtle problem with your code is that you're attaching a color to a "component" instead of attaching it right to the face. Anything referenced in an XDE document is a "prototype" (see here: https://www.analysissitus.org/features/features_asm-code-architecture.html#toc-asm-ent-prototype), no matter if that's a part, a subassembly or a subshape.

This is what your code results in (looking in the DF browser):



Notice that a color is attached to 0:1:1:1:1, which is a REFERENCE to your face. Now, let's modify your code like this:

TDF_Label newLabel = hShapeTool->AddComponent(aLabel, face.Face());
TDF_Label newLabelProto = hShapeTool->FindShape(face.Face()); // one
hColorTool->SetColor(newLabelProto, redColor, XCAFDoc_ColorSurf); // two
hColorTool->SetColor(newLabelProto, redColor, XCAFDoc_ColorGen); // three
hColorTool->SetColor(newLabelProto, redColor, XCAFDoc_ColorCurv); // four

Here we attach a color to the "prototype's" label and it results in the following structure:



Some software packages would not interpret correctly any colors associated with references and not with the prototypes. CAD Processor with your code:



With the modification:



FreeCAD on the shape with modification:



You should prefer attaching metadata to "prototypes" unless you deliberately choose to do it the other way around and use instances. In the latter case, be prepared that some CAD tools would ignore such metadata.

 

[frankpian]

@Quaoar
Thank you for your reply. This structure doesn't seem to make a lot of sense. If I have a lot of shapes with different colors but the same structure, I need to copy multiple shapes, wasting a lot of space.

 

[Quaoar]

Why "wasting lot of space"? Attaching color to face prototype is no different from attaching color to its instances in terms of space.

 

[frankpian]

Why "wasting lot of space"? Attaching color to face prototype is no different from attaching color to its instances in terms of space.

If I have 10 shapes with the same structure in different locations and different colors, I just need to set the color for each REFERENCE. But setting a color for a prototype can only have one. All references point to the same prototype

I add multiple faces in assembly. Colors are still placed on the REFERENCE. Freecad is working fine.

TDF_Label aLabel = hShapeTool->NewShape();
TDataStd_Name::Set(aLabel, "testModel");
gp_Trsf aTrsf;
for (int i = 0; i < 100; ++i) {
aTrsf.SetTranslation(gp_Vec(0, 0 + i, 0));
TopoDS_Shape theShape = BRepBuilderAPI_Transform(face.Face(), aTrsf).Shape();
TDF_Label newLabel = hShapeTool->AddComponent(aLabel, theShape);
hColorTool->SetColor(newLabel, redColor, XCAFDoc_ColorSurf);
}
hShapeTool->UpdateAssemblies();