Re: [Mesa-users] OSMesa problems with proprietary NVIDIA 304 drivers on Debian Jessie

[tom (mobile)]

If you're happy using OGL ES, you could use an EGL context instead of a GLX (or 
OSMesa) context.  Brian can correct me, but I think that will 1) always work, 
regardless of whether a GPU is there and 2) will be HW-accel'd if there is a 
GPU.

-tom

On May 16, 2015 2:13:00 AM PDT, Andreas Weber <address@hidden> wrote:
>Hi Brian, thank you for your answer.
>
>On 15.05.2015 16:35, Brian Paul wrote:
>> On 05/14/2015 03:13 PM, Andreas Weber wrote:
>>> Dear users and maintainers,
>>>
>>> we want to use OSMesa for offscreen rendering in the upcoming GNU
>Octave
>>> 4.0 release. Unfortunately I'm facing some unecpected problems when
>>> using proprietary NVIDIA 304 legacy drivers (it works fine if
>switching
>>> to nouveau or on machines with AMD or Intel GPU).
>>
>> Just to be clear, OSMesa does not work with nvidia's driver/hardware
>(or
>> any other GPU).  The OSMesa interface only works with software
>rendering
>> (swrast, softpipe, llvmpipe).  If you want to do offscreen rendering
>> with a hardware GPU, the easiest approach is to use framebuffer
>objects.
>
>I would like to be able to render OpenGL to a bitmap or, using gl2ps,
>to 
>PostScript without needing a X display or even a hardware GPU (aka 
>headless server).
>
>I'm not familiar with the Mesa or OpenGL internals so my question might
>
>sound naive but how can I force a program to use swrast, softpipe or 
>llvmpipe? I tired setting LIBGL_ALWAYS_SOFTWARE=1 but apparently this 
>doesn't work if the Nvidia drivers are installed. And why does osdemo 
>work even if Nvidia drivers are installed but Octave not? Some compile 
>or linker flags?
>
>>> The problem is that the generated image is almost black and values
>>> queried with glGetIntegerv contains arbitray values, for example
>>> ...
>> My guess is you're calling glGetIntegerv() without having a current
>> rendering context.  The values you're getting are probably the
>> uninitialized values of z, s, ar, etc.
>
>Yes, you are right this was the reason. I though if OSMesaContext and 
>OSMesaCreateContextExt return without error I can assume that there is
>a 
>current rendering context.
>
>-- Andy
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