[Mesa3d-dev] GLX_MESA_render_texture

[David Reveman]

On Wed, 2005-06-08 at 17:07 -0700, Ian Romanick wrote:
> David Reveman wrote:
> > On Wed, 2005-06-08 at 11:06 -0700, Ian Romanick wrote: 
> > 
> >>Also, I'm pretty sure that ATI ships a version of this in their drivers,
> >>and I think Nvidia might as well.  If we are going to move forward with
> >>this, it would be nice to have all three implementations play nice
> >>together.  That would probably mean making this a GLX_EXT instead of
> >>GLX_MESA.
> > 
> > Yes, I guess that would be nice.
> > 
> > The big difference between GLX_MESA_render_texture and
> > WGL_ARB_render_texture (GLX_ATI_render_texture as well I guess) right
> > now is that MESA_render_texture can be used not only with pbuffers but
> > with any GL drawable. Having support for GLXPixmaps makes it possible to
> > bind redirected windows to textures and that's what we like to do.
> 
> Currently, WGL_ARB_render_texture works by modifying wglCreatePbuffer to
> accept an attribute that says you intend to bind the pbuffer to a
> texture.  I see no reason why glXCreateWindow and glXCreatePixmap could
> not get the same treatment.  The driver would just have to be careful
> about the fbconfigs that it exports.  So, if the driver can't map a
> window to a texture, don't export an fbconfig with both
> BIND_TO_TEXTURE_* set to true and DRAWABLE_TYPE with WINDOW_BIT set.

Makes sense. I was making it harder than necessary.

> 
> The catch to all of this is that it more and more requires GLX 1.3. :(

Yes, I wonder how much work that will be...

> 
> > We can have GLX_EXT_render_texture not support anything else than
> > pbuffers but then we'll need an additional extension for creating a
> > pbuffer from a redirected window or a pixmap. A new attribute for
> > glXCreatePbuffer would probably be enough for such an extension. If we
> > want a GLX_EXT_render_texture this might be a good idea, but do you
> > think Nvidia and ATI really care about a GLX_EXT_render_texture now that
> > we've got GL_EXT_framebuffer_object?
> 
> If we spec it the way I described above, they could all the
> GLX_EXT_render_texture string to their drivers with essentially no
> changes.  Whether or not they want to export fbconfigs that allow
> binding of windows or pixmaps to textures will depend 100% on market
> pressure and the required effort.

Exactly.

> 
> > I do hope that they can have the necessary client-side support so that
> > their GL libraries can be used with indirect rendering clients running
> > on top of Xgl that like to use this functionality. 
> 
> Hopefully ATI will end up using the "standard" X.org libGL on the
> client-side.  Since they use DRI, there shouldn't be any technical
> reason to prevent it (aside from missing functionality that they may
> require).  Nvidia, on the other, will have to add that protocol support.
> 
> 
> 
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-David