A chat log from last night's chat with NVIDIA is up on Bjorn3D
Along the way, the proceedings point the way to a forum post called Half-Life 2 - Anti-aliasing
by Valve's Gabe Newell that puts the recently unveiled "problem" with
HL2 antialiasing (story
) in perspective: He explains how the visual artifacts
described in recent reports have been present in other games for years, and that
they are showing concern because they have eliminated so many other visual
artifacts as well as the amount of light variation they are using. He goes on to
2) What are potential solutions?
- Support Centroid Sampling
- Use Pixel Shaders to Clamp Texture Coordinates
Centroid sampling doesn't have the problem that center sampling does
in multi-sample antil-aliasing. ATI has supported this form of anti-aliasing for
the 9000 series. The tricky part is enabling this when DirectX doesn't easily
There's a different trick you can use with hardware, such as NVIDIA's, that
doesn't support centroid sampling. Basically you trade off some pixel shader
bandwidth to clamp the texture coordinates so that you don't sample texels
outside of that polygon's lightmap sub-rect.
Between these two approaches, multi-sample anti-aliasing artifacts should be a
non-issue for any DX9-level hardware running Pixel Shader 2.0.
3) How will this look?
We'll release one of the demo movies with the anti-aliasing artifacts in and one
with the anti-aliasing changes.