Originally posted by canadian_divx
ah good point, thanks everyone

Originally posted by Sazar
nvidia has a software fix in the works from the sounds of it... whereas ati's implementation AFAIK should be hardware based... ergo faster...

Originally posted by Electronic Punk
That sounds like it kinda contradicts what the original xbitlabs article. You make it sound as if nvidia can provide a software (driver) fix but ati cannot... a hardware implementation sounds like you have to mod your card .. or update the bios?

Tell us what you know

1) Is this a problem that can be fixed with new drivers, or would we have to buy a whole new card to recitify it? If so, are there any cards on the horizon that would offer it?

Drivers aren't likely to fix the problem, with the exception of the ATI 9500-9800. There's hope there for being able to use FSAA properly. You are out of luck on NVidia unless either NVidia or us come up with some clever way of solving this problem.

2) Is this a problem unique to hardware + Source?

It's a problem for any app that packs small textures into larger textures. The small textures will bleed into each other if you have multisample FSAA enabled. The best thing to do right now is either buy an ATI card in the hopes that it will be solved there, or wait until the next generation of cards come out.

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.

The highly-anticipated Half-Life 2 game will have a major bug with current DirectX 9.0 hardware resulting in impossibility in enabling Full-Scene Anti-Aliasing, a popular feature that dramatically improves image quality in games. Apparently, there is a limitation in DirectX 9.0 and/or DirectX 9.0-compliant hardware that will not allow the function to be enabled on certain graphics cards if the workaround is not found.

According a Valve officials quoted in forums at HalfLife2.net web-site, there are problems with the way that current hardware implements FSAA. If you enable it, you will see a lot of artifacts on polygon boundaries due to the way that current graphics processors sample texture subjects with FSAA enabled.

Valve continued that this is a problem for any application that packs small textures into larger textures. The small textures will bleed into each other if you have multi-sample FSAA enabled.

Currently both leading graphics chips designers use multi-sampling or hybrid multi-sampling + super-sampling methods to for FSAA.

The developers of the legendary Half-Life game said that drivers are not likely to solve the problem, however, it still can be solved for graphics cards based on VPUs from ATI Technologies, such as RADEON 9500-, 9600-, 9700- and 9800-series. As for NVIDIA GeForce and GeForce FX-series, there are practically no chances to find a workaround, according to Valve.

Some industry sources indicated that the problem with such FSAA is a known one and is to be addressed in DirectX 9.1 and next-generation graphics processors with Pixel Shaders 3.0 and Vertex Shaders 3.0, such as ATI Technologies’s code-named R420 and NVIDIA’s code-named NV40 VPUs and derivatives. Both next-generation products will come later than the Half-Life 2 that is expected to be available by October.

You can find the thread on the matter with quotes from Valve officials here .

Stay tuned with us because we are looking forward to bring you some comments from ATI Technologies and NVIDIA about the situation.