[cairo] glitz and shader programs

Jon Smirl jonsmirl at yahoo.com
Mon Apr 26 13:39:35 PDT 2004

There are zero open source shader implementations and no hardware manufacturer
has released the docs needed to build one. Since we need Mesa to build a
standalone OpenGL there is no solution for Mesa and glitz.

--- David Reveman <c99drn at cs.umu.se> wrote:
> On Mon, 2004-04-26 at 09:53 -0700, Jon Smirl wrote:
> > Is it possible to implement the Cairo API without resorting to OpenGL shader
> > programs while still keeping thing accelerated? I know glitz currently uses
> > these, but can their use be eliminated without impacting performance?
> There's a
> > lot of 3D hardware out there that doesn't support them.
> I've managed to get the most imporatant compositing operations with mask
> surfaces working only with multi-texturing. I'll clean up the code, do
> some more testing and commit it later this week. With this working, only
> gradients will require shaders for acceleration (I'm not counting
> cairo's Gaussian filter type as no other backends than the OpenGL
> backend currently supports it).
> I'm sure that also the gradients can be rendered without shaders. It's
> actually possible with the current version of glitz by using
> non-rectangular clipping and color triangles but I don't like that
> solution as it will be very complex, especially with multiple color
> stops. I'm currently looking at other solutions...
> I doubt that we can eliminate all shaders without impacting performance.
> Filling a path using a radial gradient with the current version of glitz
> is almost as fast as filling it with a solid color.
> I don't think that we should spend to much time trying to eliminate the
> use of shaders. Shaders are extremely flexible and efficient. Hardware
> vendors also tend to support them better and better. So, if we like to
> compete with microsoft and apple, I think that instead of trying to
> eliminate shaders, we should try build a system that is designed for
> efficient use of them. This is what's going to be important in the
> future.
> - David
> -- 
> David Reveman <c99drn at cs.umu.se>

Jon Smirl
jonsmirl at yahoo.com

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