OffscreenRendering on Windows
Hi, I have encountered some problems with the OffscreenRendering example. I am using Windows 10 and VTK-9.3.0.rc1 compiled with osmesa (https://github.com/pal1000/mesa-dist-win/releases).
It may be wrong to use the vtkRenderWindow class since vtkWindowToImageFilter internally calls the GetPixelData() - this is a virtual method of vtkWindow, which just returns nullptr. vtkRenderWindow derives from vtkWindow and does not override this method. Alternatively the GetRGBACharPixelData() method from vtkRenderWindow is called, also returning nullptr. Furthermore, vtkWindowToImageFilter does not check obtained pointer for nullptr, so an invalid memory acccess error occures as soon as the filter tries to use the non-existing pixel data.
Replacing vtkRenderWindow with vtkOSOpenGLRenderWindow solved the problem. Maybe it is worth to add a comment about replacing vtkRenderWindow with a window class supporting GetPixelData?