“Since
people seem to be hyperventilating over the anti-aliasing issue,
I thought I'd
update everyone.
1) How bad is the problem?
With current multi-sample implementations of anti-aliasing, you may sample
texels outside of the polygon boundary, which may result in sampling light
maps from other polygons.
This has always been a problem. This is a problem with Quake 1, Quake 2, Quake
3, Daikatana, Sin, Elite Force, Half-Life, Counter-Strike on the X-Box, or
any game that uses packed lightmaps with multi-sample anti-aliasing.
You would see these artifacts on polygon boundaries where the wrong lightmap
is being sampled. It will look like a bright or dark line on the edge of a
polygon.
Gary McTaggart brought this up in an email because he is being pretty hardcore
about graphics quality right now. This is not a new problem. If you've run
a game that uses lightmaps with anti-aliasing turned on, then you've been seeing
these artifacts the whole time.
Artifacts may show up more frequently in Half-Life 2 simply because we've
eliminated lots of other artifacts, and because we have a lot of variation
in scene lighting due to our art direction.
To put this in perspective, not doing tri-linear filtering on mipmaps is a
lot worse.
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 expose this.
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.”
Here we can see the heat sink fan unit on the Radeon 9800 Pro and Radeon
9700 Pro. As we can see here the Radeon 9700 Pro’s heat sink fan was
nothing spectacular and was common among all ATi Video cards for quite some
time now. The Radeon 9800 Pro’s heat sink fan was welcome to be changed
as I never fancied the black and boring heat sink fan on their cards. As you
can see, the simple change of a heat sink fan makes a world of a difference
in the final looks of the product.
