[vtkusers] Gradients computation speed-up in vtkFixedPointVolumeRayCastMapper by multi-threading

[Lasso, Andras (GE Healthcare)]

Hi all,
 
I use vtkFixedPointVolumeRayCastMapper for volume rendering. The image
quality is perfect, but I have to wait about 30 sec for the first
rendered image, mainly due gradient computation.
 
Currently (VTK-5.0.3) the gradient computation is implemented in a
single thread. I would expect that on multi-core/CPU systems the
gradient computation could be made 2-4 times faster with a
multi-threaded implementation. Looking at the code I've found that the
algorithm in vtkFixedPointVolumeRayCastMapperComputeGradients is already
prepared for a multi-threaded implementation.
 
Does anyone know why the multi-threaded gradient computation just
prepared, and finally not implemented for
vtkFixedPointVolumeRayCastMapper?
 
Andras
 
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