ATI Radeon 9700 Dissected

Bender writes "The guys who laid out the future of real-time graphics a while back have now dissected ATI's Radeon 9700 chip. Their analysis breaks down performance into multiple components--fill rate, occlusion detection, pixel shaders, vertex shaders, antialiasing--and tests each one synthetically before moving on to the usual application tests like SPECviewperf and UT 2003. You can see exactly how this chip advances the state of the art in graphics, piece by piece. Interesting stuff."

Comments

Enthusiasm for procedural shaders

[Animats]

There seems to be considerable enthusiasm for procedural shaders amongst graphics card designers. This is not necessarily shared by animators.

It's partly a working style issue. Texture-map people go out with cameras and photograph nice-looking surfaces, which they then apply to models. Or they paint the textures. Procedural shader people try to code up the "meaning" of a texture. Texture maps are created by artists; procedural shaders are created by programmers.

The basic problem with texture maps, of course, is that you can't get too close before the texture gets blurry and the illusion breaks down. In film work, you know where the camera is, so you can figure out how much texture detail you need. Games don't have that luxury; you can get close to a surface and blow the illusion.

Most film work other than Pixar's has used texture maps. There are exceptions, but they're typically for hair, fur, and water, where the problem is motion.

The price you pay for using procedural shaders is that they usually model surface, not detail. So you have to model the detail. Lots of it. Again, Pixar is notorious for this. ("We modelled the threads on the screws, even though you couldn't see them!")

Texture maps, bump maps, and displacement maps can be used to modulate procedural shaders, and that's probably how surface detail will be done, rather than getting carried away with building complex textures in some programming language.

Re:Enthusiasm for procedural shaders

[Crag]

It's not just the pixelation or blurring that procedural shaders solve. Combined with other techniques such as bump and environment mapping, surfaces can be given depth without increasing the poly count. A texture can be be made to look like water without transmitting wave information to the video card. Just send a function.

The combination of pixel and vertex shaders allows stunning effects like flag that flaps in the wind and still casts the right shadows, and it's all done on the card (an example I stole from an NVidia presentation).

It's no cure-all, but it is another large step forward.

ATI isn't even on the chart.

[Nailer]

Every NVIDIA card since the GeForce2 Ultra has had Linux drivers before they even hit the shelves. This is because Nvidia pay people to write and maintain the drivers. They might not have specs, but at least NVidia support your choice of operating system.

ATI release some specs, and that's all. They don't either bother writing drivers for their cards and they just hope someone else will - *maybe the weather channel, maybe soon, maybe later, maybe not for your specific card) or release binary-only drivers (great, at least they exist) that don't have anything like the performance of their Windows drivers. The UT2003 benchmark, if ran under Linux, won't even start on a Radeon 8500 (which ATI do have fast, binary only drivers for because its missing correct support for S3 texture compression. Which isn't exactly a new technology by any means.

So I can get Open Source 2D support for a Radeon 9700? Great. I'm sure 2D support is why people buy a Radeon 9700.

Vote with your dollars.