[vtk-developers] OSMesa depth buffer issues

[Francois Bertel]

Hi Burlen,

I just looked at vtkWindow/vtkRenderWindow and too bad, there is no
API to let the user specify the render window settings regarding the
depth in bit of each type of buffer (color buffer, depth buffer,
stencil buffer, accumulation buffers) in the framebuffer.
That would have be better than hardcoding the values in vtkXOpenGLRenderWindow.

Anyway the typical values for on-screen are 24 bits for depth buffer,
8 bits for stencil buffer, 16 bits per channel for accumulation
buffer.
What happen in your case if you use these values instead the one you
provided in your patch?

On Thu, Jan 28, 2010 at 4:14 PM, burlen <burlen.loring at gmail.com> wrote:
> 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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