Off screen rendering with GLX pixmaps

[Roderick Colenbrander]

> Hi,
> 
> I'm trying to use GLX pixmaps to implement OpenGL off screen rendering
> but I can't get it working on one of my box. I'm getting GLXBadContext
> when I call glXMakeCurrent. I attached an example of the not working code.
> 
> The same code works on my other box and I guess the problem may come
> >from my graphic card. Now, how can I get off screen rendering working on
> any configuration? Or, at least, how can I test that off screen rendering
> is
> impossible?
> 
> Guillaume

First of all why do you want to use GLXPixmaps for off screen rendering? Most drivers don't accelerate it all. At least modern Nvidia drivers accelerate it and I think AIGLX capable drivers (I have no experience with AIGLX).

Most other drivers (which use DRI) fall back to indirect rendering most of the time the drivers turn into plain Mesa. It might not support the XVisual you are presenting it, plain Mesa can have strange issues. For instance if I remember correctly it doesn't support single buffered visuals (at least those don't show up in glxinfo if you use plain Mesa) and that could be your problem. Try asking for a double buffered visual.

Really if you want to use off screen rendering also consider the use of pbuffers (though not all drivers support them) and even better on more modern drivers FBOs.

Regards,
Roderick


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