[vtkusers] Mangled Mesa Volume Rendering

[Kevin H. Hobbs]

On Tue, 2006-05-09 at 14:02 -0400, Kevin H. Hobbs wrote:
> I've slowly been isolating my problem with making a volume rendered
> movie offscreen on our MPI cluster.
> 
> I'm using VTK from CVS.
> 
> The mangled Mesa I've been using most is version 6.4.2.
> 
> The example VTK/Examples/MangledMesa/Tcl/OffScreenCone.tcl works but the
> attached code, based off of it and
> VTK/Examples/VolumeRendering/Tcl/IntermixedUnstructuredGrid.tcl, does
> not work. I just get a black image.
> 
> An added annoyance is that when I build VTK with mangled mesa regular
> rendering segfaults.

It seems I was using the wrong threshold. So The GL version was
correctly rendering a black and transparent volume on a black
background. After fixing that, I think I have the problem isolated to
Offscreen Volume Rendering alone.

The attached OSVolumeRender.cxx can easily be switched between
off-screen and on-screen rendering with a few comments.

When vtkRenderer and vtkRenderWindow are used, the SetOffScreenRendering
line is commented out, and I use my VTK without mangled mesa the program
works.

When vtkMesaRenderer and vtkXMesaRenderWindow are used, the
SetOffScreenRendering line is included, and my VTK with mangled mesa is
used, the program segfaults at render().

Again, onscreen rendering works, offscreen rendering works, onscreen
volume rendering works, offscreen volume rendering does not work.
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