[vtkusers] vtkGPUVolumeRayCastMapper: Updateing ImageData after first Rendering?

Willy Wiggerl at Linhuber.info
Mon Feb 20 07:59:03 EST 2017

I found a bit information about the 1m 29 s wait time. The first call of
vtkOpenGLGPUVolumeRayCastMapper::GPURender calls
vtkVolumeTexture::LoadVolume and that calls vtkDataArray::GetRange and that
method loops through my 3GB scalar data and calls each time min and max (to
get the min and max value of all values). Can i prevent vtk from doing that?
Why does vtk even calculate that? Does vtk maybe want to scale the
greyvalues bewenn min and max? Maybe i can disable that somehow?

Moreover i tested a application named ParaView (ParaView uses vtk too).
ParaView does not wait 1m29s. It seems like it is not neccessary to
calculate min and max.

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