[vtkusers] offscreen rendering from gui application in vtk8/opengl2

Andreas Buykx A.Buykx at dianafea.com
Mon Jul 9 03:42:27 EDT 2018

We recently switched our FEA application from vtk7.1 and the OpenGL backend to using 8.1 and the new OpenGL2 backend.

With 7.1 we could make off-screen images from the gui application using a temporary off-screen render window, temporarily moving renderers from the GUI render window to the off-screen render window, render the image and then move all renderers back to the GUI render window.
With vtk8.1 and OpenGL2 this causes OpenGL errors.

I reproduced this with the attached script which on vtk8.1.1 and the current head leads to an openGL error:

ERROR: In path-to/VTK-master/Rendering/OpenGL2/vtkOpenGLPolyDataMapper.cxx, line 1814
vtkOpenGLPolyDataMapper (0x273dc00): failed after UpdateShader 1 OpenGL errors detected
  0 : (1282) Invalid operation

When the script is run with a global off-screen render window things work out fine.

Is my approach wrong (temporary render window, moving renderers to it temporarily) or is this a bug?

Thanks for your help!

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