[vtkusers] Volume rendering Shading with dependent components

[Benoit Bleuze]

And as for the rendering mode I meant vtkGPUVolumeRayCastMapper of course, not my own member (vtkSmartVolumeMapper::GPURenderMode) which doesn't mean anything to you all.

----- Original Message -----
> Hi list,
> 
> I have encountered this strange behaviour in VTK recently and wanted
> some knowledgeable vtk people to shade some light on it:
> 
> I am doing volume rendering of an rgba volume.
> To do this I set the following 2 vtkVolume properties:
> 
> vtkVolumeProperty::IndependentComponentsOff()
> and vtkVolumeProperty::ShadeOn()
> 
> I use the GPU Rendering: vtkSmartVolumeMapper::GPURenderMode
> 
> As a result, if I compile vtk in debug mode I stumble upon this
> failing assert call,
> in vtkOpenGLGPUVolumeRayCastMapper.cxx, line 4159 in vtk 5.8.0 (in git
> at this time it's on line 4152),
> in the following method:
> 
> void vtkOpenGLGPUVolumeRayCastMapper::PreRender(vtkRenderer *ren,
> vtkVolume *vol,
> double datasetBounds[6],
> double scalarRange[2],
> int numberOfScalarComponents,
> unsigned int numberOfLevels)
> [...]
> if ( vol->GetProperty()->GetShade() )
> {
> shadeMethod=vtkOpenGLGPUVolumeRayCastMapperShadeYes;
> assert("check: only_1_component_todo" && numberOfScalarComponents==1);
> }
> 
> [...]
> 
> 
> If I run the same code in Release mode, nothing goes wrong and there
> is indeed shading performed on my rgba data.
> Should this assert be removed, or is shading on dependent components
> not something to do?
> 
> Thank you for the insight.
> 
> Ben.
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