[vtk-developers] OSMesa depth buffer issues

[burlen]

Hi Guys,

I'm having some issues in ParaView that relate back to VTK's OSMesa 
rendering context. Specifically VTK asks OSMesa for the default RGBA 
context, which only has a 16 bit depth buffer. That's causing some 
artifacts and compositing issues in certain situations. for example:

    http://nashi-submaster.ucsd.edu/movies/PV/tube-filter-artifact/mesa-artifacts.png
    http://nashi-submaster.ucsd.edu/movies/PV/tube-filter-artifact/mesa-artifacts-decomp.png

Explicitly requesting a 32 bit depth buffer solves the problems.

I attached a small patch that makes this change in VTK. It replaces the 
call to OSMesaCreateContext with one to OSMesaCreateContextExt 
specifying a 32 bit depth buffer and carries forward the current default 
values for accumulation and stencil buffers. I guess this function was 
The OSMesaCreateContextExt was added to in mesa release 3.5, the current 
release is 7.7.

Is this the right fix? Or is something more sophisticated necessary? 
e.g. run time configurable. And while we're on the subject, are OSMesa's 
other buffer defaults reasonable? accum (8 bits per channel) and stencil 
buffers (16 bits).

Thanks
Burlen

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