[vtk-developers] OSMesa depth buffer issues

[Francois Bertel]

Excellent point!

On Thu, Jan 28, 2010 at 4:33 PM, Jeff Lee <jeff at cdnorthamerica.com> wrote:
> I am surprised it doesn't honor
>
>  MESA_GLX_DEPTH_BITS=24
>  export MESA_GLX_DEPTH_BITS
>
> - this seems to work fine for me.
> -Jeff
>
> On Thu, Jan 28, 2010 at 4:30 PM, Francois Bertel
> <francois.bertel at kitware.com> wrote:
>>
>> 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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>> >
>>
>>
>>
>> --
>> François Bertel, PhD  | Kitware Inc. Suite 204
>> 1 (518) 371 3971 x113 | 28 Corporate Drive
>>                      | Clifton Park NY 12065, USA
>> _______________________________________________
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>
>



-- 
François Bertel, PhD  | Kitware Inc. Suite 204
1 (518) 371 3971 x113 | 28 Corporate Drive
                      | Clifton Park NY 12065, USA