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SubjectRe: HARDWARE: Open-Source-Friendly Graphics Cards -- Viable?
Alan Cox <> wrote:

> I've actually always wondered what a hybrid video device would
> look like for 3D. Doing the alpha blend and very basic operations
> only in the hardware that are expensive in software - alpha and
> perhaps some of the texture scaling, but walking textures in
> software, doing shaders in software and so on.

Well that is what most of the early 3D cards started out as. A lot of the
early SGI boxes that has '3D' were not full 3D rendering engines but span
based rendering engines. Not only was setup done in software, but so was
the walking of the triangle sides and the only thing passed to the
hardware was commands to render spans (flat, smooth or textured). You
could build any kind of complex renderer on top of this and in those days
it was SGI GL (pre OpenGL) that was the rendering API. The systems were
also reasonably fast for the day too.

I think the original 3DLabs GLINT SX chipset also did span rendering and
support textured spans. The biggest problem is that the overhead required
by the CPU to process anything close to the volume of triangles per
second that high end cards can handle today is overwhelming. Even a 4Ghz
P4 probably couldn't keep up trying to match the transform, lighting and
span traversal to match even a basic Radeon 9000 card IMHO. And then
you've got no CPU cycles left for anything else such as sound and game
physics ;-)


Kendall Bennett
Chief Executive Officer
SciTech Software, Inc.
Phone: (530) 894 8400

~ SciTech SNAP - The future of device driver technology! ~

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