Bug#642368: libgl1-mesa-dri: Issues with OpenGL point size

[Julien Cristau <jcristau@debian.org>]

On Thu, Sep 22, 2011 at 01:05:18 +0200, Sylvain Beucler wrote:

> Package: libgl1-mesa-dri
> Version: 7.11-5
> Severity: important
> 
> Hi,
> 
> When testing Guus' excellent tutorial:
> http://en.wikibooks.org/wiki/OpenGL_Programming/Scientific_OpenGL_Tutorial_01
> we spotted a few issues in the software and radeon renderers linked to
> the point size feature in OpenGL.
> 
> Attached is a sample program.  You can press F1/F2/F3 to switch
> between lines/dots/point-sprites rendering, what interests us here are
> dots and point-sprites.
> 
> - Under Radeon, all modes get color artifacts (memory-corruption-like
>   colors are displayed instead of a shade of blue).
> 
> - Dots are not working with LIBGL_ALWAYS_SOFTWARE=1: variable dots
>   size instead of fixed size (it seems to use gl_Position.x as point
>   size).  Point sprites seem to have a similar issue.
> 
> - Dots are showned properly on an IntelGPU+Ubuntu environment, and
>   under windows with radeon 9600, making me suggest the problem lies
>   in the OpenGL implementation rather than in the code.
> 
> Dots and point-sprites are not common in games, but more in scientific
> applications.
> 
You should probably take this up on the mesa-dev@lists.freedesktop.org
list, where the radeon developers will have a better chance of figuring
this out.

Cheers,
Julien