[Mesa-users] Question about support for OpenGL 3.2 Core context

[Albert Freeman]

On 25 November 2015 at 22:45, Ken Martin <ken.martin at kitware.com> wrote:
>
> Noob question incoming... I have an application that requests a 3.2 core
> context from Mesa.  I tell folks to make sure they have mesa version 10.6.5
> or later which I thought supported OpenGL 3.2.  Usually this works but now
> and then I get users who's Mesa (including version 11) fails to provide a
> 3.2 Core context. I tell them to set
>
> MESA_GL_VERSION_OVERRIDE=3.2
>
> and
>
> MESA_GLSL_VERSION_OVERRIDE=150 (or something like that)
>
> and it generally works. But I'm not sure why the original request for 3.2
> Core is failing on some systems (drivers?).  Looking at
>
> http://mesamatrix.net/
>
> leads me to think that all drivers with a recent mesa should be fine with
> 3.2 Core but obviously I am missing something. Do I need to be telling them
> to use a specific driver? Is there a list of drivers that do not support 3.2
> I should tell them to avoid? Anything else come to mind?
>
> I just want to try to provide a bit more help to folks to get them up and
> running with Mesa and even better get our code to handle it automatically if
> we could.
>
> Any pointers appreciated. The application is vtk.
>
> Thanks
> Ken
>
>
>
>
>
>
>
> --
> Ken Martin PhD
> Chairman & CFO
> Kitware Inc.
> 28 Corporate Drive
> Clifton Park NY 12065
> 518 371 3971
>
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Not all mesa drivers support gl 3.2, e.g. the r300 gallium driver in
the git mesa supports only glsl 1.20:
        case PIPE_CAP_GLSL_FEATURE_LEVEL:
            return 120;

That website is based on gl3.txt. It does not list all drivers mesa
supports (as gl3.txt dosen't). They are both only meant to be a rough
guide. The svga driver apparently supports gl 3.3 and it isn't even
mentioned in gl3.txt. So I think some of the vtk users have really old
gpus that don't support gl 3.2. Some gl versions already have software
emulated components for gl features not supported by the hardware on
older gpus and some older gpus simply don't have support.