Support PLY with texture coordinates parameters named (s, t)

Development
1

Hello,

I am using vtkPLYReader to import various PLY meshes in my project (python VTK 9.5.2).

I have a problem with some PLY file formats that use external texture : the vtkPLYReader fails to parse texture coordinates on some of them. So I lost all information about texture and can’t display correctly the mesh color.

It seems VTK (9.5.2) currently only support texture coordinates expressed using properties named (u, v) or (texture_u, texture_v), and doesn’t support (s, t) which is also frequently used.

Is it possible to add support for these parameters name?

After checking the vtkPLYReader.cxx, it seems it’s doable by adapting a few lines:

int vtkPLYReader::RequestData(vtkInformation* vtkNotUsed(request),
  vtkInformationVector** vtkNotUsed(inputVector), vtkInformationVector* outputVector)
{
...

  bool texCoordsPointsAvailable = false;
  vtkSmartPointer<vtkFloatArray> texCoordsPoints = nullptr;
  if ((elem = vtkPLY::find_element(ply, "vertex")) != nullptr)
  {
    if (vtkPLY::find_property(elem, "u", &index) != nullptr &&
      vtkPLY::find_property(elem, "v", &index) != nullptr)
    {
      texCoordsPointsAvailable = true;
    }
    else if (vtkPLY::find_property(elem, "texture_u", &index) != nullptr &&
      vtkPLY::find_property(elem, "texture_v", &index) != nullptr)
    {
      texCoordsPointsAvailable = true;
      vertProps[3].name = "texture_u";
      vertProps[4].name = "texture_v";
    }
    else if (vtkPLY::find_property(elem, "s", &index) != nullptr &&
      vtkPLY::find_property(elem, "t", &index) != nullptr)
    {
      texCoordsPointsAvailable = true;
      vertProps[3].name = "s";
      vertProps[4].name = "t";
    }

    if (texCoordsPointsAvailable)
    {
      texCoordsPoints = vtkSmartPointer<vtkFloatArray>::New();
      texCoordsPoints->SetName("TCoords");
      texCoordsPoints->SetNumberOfComponents(2);
      output->GetPointData()->SetTCoords(texCoordsPoints);
    }
  }
...
}

Please correct me if I’m wrong.