OpenGL2 backend randomly results in wrong colors with vtkCompositePolyDataMapper/vtkMultiBlockDataSet
The OpenGL2 backend randomly gives some primitives the wrong colors or the wrong point locations for primitives when there are shared vtkPoints or shared vtkPointData arrays.
See this example which demonstrates the wrong coloring: test.py
And here is the expected image, which I always get with the OpenGL backend, and sometimes get with the OpenGL2 backend.
And here is the image I sometimes/often get with the OpenGL2 backend.
My workaround is to do deep copies to avoid sharing data. Perhaps this has something to do with the VBO cache.