Messages in this thread | | | Date | Fri, 22 Oct 2004 13:15:04 -0400 | From | Timothy Miller <> | Subject | Re: HARDWARE: Open-Source-Friendly Graphics Cards -- Viable? |
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Kendall Bennett wrote:
> > 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 ;-) >
The bus (PCI, AGP, whatever) is a much more severe bottleneck than even the CPU.
If it takes two-dozen parameters to specify a triangle that ends up plotting only a single pixel on the screen, it's just not worth doing. But that is something that happens a lot onboard 3D chips. That's why triangle rate is as important a factor as pixel rate.
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