Color bugs when converting assembly from OCCT to VTK

[DanB]

This problem has been bugging me for days. We have built a pipeline converting an assembly from TopoDS to VTK polydata. Where we use the recursive method proposed by @Quaoar in the youtube video about assembly's to read the assembly before converting. Using XCAFDoc_ColorTool::GetColor() to get colors from the step-file, then we write the colors to a vtkColorTransferFunction lookUpTable - and further use this to set the colors to the vtkMapper based on IDs. For reasons I cannot understand, some sub-shapes get the wrong color. Is someone able to spot our error, or have an explanation for this?

Color bug:

Correct colors from FreeCad:


This is the function generating the colormap:


The input to createColorMap comes from this iterator going through all shapes:

DisplayShape:

 

[natalia]

It would be useful for investigation if you attach the STEP file of this case.

 

[DanB]

It would be useful for investigation if you attach the STEP file of this case.

The file is now attached

 

[natalia]

The result of the sample proposed by @Quaoar in the youtube video

for this file looks:


That means that colours read from this STEP, later transformed into an OCAF document and shown through AIS presentations are valid.

So comparing two pieces of the code might solve wrong appearance. The first one is from the youtube lesson, which is placed in the "Lesson12_XDE" directory of https://gitlab.com/ssv/lessons and the current implementation.

The recursive processing is different. Less recursion in the attached code leads to skipping some children colours. To compare:

  // In case of an assembly, move on to the nested component.
  for ( TDF_ChildIterator childIt(refLabel); childIt.More(); childIt.Next() )
  {
    TDF_Label childLabel = childIt.Value();

    if ( !childLabel.IsNull() && ( childLabel.HasAttribute() || childLabel.HasChild() ) )
    {
      TopLoc_Location trsf = parentTrsf * ShapeTool->GetLocation(childLabel);
      this->displayItem(childLabel, trsf, defStyle, itemId, mapOfOriginals);
    }
  }

Following this code should fix vtk result.

 

[DanB]

The result of the sample proposed by @Quaoar in the youtube video

for this file looks:

View attachment 163
That means that colours read from this STEP, later transformed into an OCAF document and shown through AIS presentations are valid.

So comparing two pieces of the code might solve wrong appearance. The first one is from the youtube lesson, which is placed in the "Lesson12_XDE" directory of https://gitlab.com/ssv/lessons and the current implementation.

The recursive processing is different. Less recursion in the attached code leads to skipping some children colours. To compare:

  // In case of an assembly, move on to the nested component.
  for ( TDF_ChildIterator childIt(refLabel); childIt.More(); childIt.Next() )
  {
    TDF_Label childLabel = childIt.Value();

    if ( !childLabel.IsNull() && ( childLabel.HasAttribute() || childLabel.HasChild() ) )
    {
      TopLoc_Location trsf = parentTrsf * ShapeTool->GetLocation(childLabel);
      this->displayItem(childLabel, trsf, defStyle, itemId, mapOfOriginals);
    }
  }

Following this code should fix vtk result.

Sorry for the late reply.

So if I understand you correctly: we need to use DisplayShape inside the first if-statement as well?

 

[natalia]

Hi, @DanB. Yes, you understand correctly. Here, you might either get this method as is or repeat the logic of it in your implementation taking care of the similar recursion.

 

[DanB]

Hi, @DanB. Yes, you understand correctly. Here, you might either get this method as is or repeate the logic of it in your implementation taking care of the similar recurce.

Thank you, Natalia