Half-life & Video Issues
MonsieurEvil
Join Date: 2002-01-22 Member: 4Members, Retired Developer, NS1 Playtester, Contributor
Join Date: 2002-01-22 Member: 4Members, Retired Developer, NS1 Playtester, Contributor
in Off-Topic
<div class="IPBDescription">Finally- some real word from all parties</div> First off, read this to get some background - <a href='http://www.bluesnews.com/cgi-bin/board.pl?action=viewthread&threadid=43067' target='_blank'>http://www.bluesnews.com/cgi-bin/board.pl?...&threadid=43067</a>
Then, read some better explanation of the real issue from Gabe Newell (CEO of valve)
<!--QuoteBegin--></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> <a href='http://www.halflife2.net/forums/showthread.php?s=&threadid=3071' target='_blank'>http://www.halflife2.net/forums/showthread...=&threadid=3071</a>
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.
_________________
Gabe Newell<!--QuoteEnd--></td></tr></table><span class='postcolor'><!--QuoteEEnd-->
And then (finally monsenub!), if you dig through this interview ( <a href='http://www.bjorn3d.com/_preview.php?articleID=313' target='_blank'>http://www.bjorn3d.com/_preview.php?articleID=313</a> )with a product manager at Nvidia yesterday, they make claim that:
<!--QuoteBegin--></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->[01:22] [NV_Ben] I am. We have a great relationship with those guys and I am confident we'll sort it out.<!--QuoteEnd--></td></tr></table><span class='postcolor'><!--QuoteEEnd-->
So, there you have it. The main issue being, even if they *don't* sort it out, it's a problem you've had your whole 3D life and just weren't aware of it. Sort of like silverfox, who was born with a huge rock in his head instead of a brain. Only showed up in routine x-rays...
XD
Then, read some better explanation of the real issue from Gabe Newell (CEO of valve)
<!--QuoteBegin--></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> <a href='http://www.halflife2.net/forums/showthread.php?s=&threadid=3071' target='_blank'>http://www.halflife2.net/forums/showthread...=&threadid=3071</a>
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.
_________________
Gabe Newell<!--QuoteEnd--></td></tr></table><span class='postcolor'><!--QuoteEEnd-->
And then (finally monsenub!), if you dig through this interview ( <a href='http://www.bjorn3d.com/_preview.php?articleID=313' target='_blank'>http://www.bjorn3d.com/_preview.php?articleID=313</a> )with a product manager at Nvidia yesterday, they make claim that:
<!--QuoteBegin--></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> </td></tr><tr><td id='QUOTE'><!--QuoteEBegin-->[01:22] [NV_Ben] I am. We have a great relationship with those guys and I am confident we'll sort it out.<!--QuoteEnd--></td></tr></table><span class='postcolor'><!--QuoteEEnd-->
So, there you have it. The main issue being, even if they *don't* sort it out, it's a problem you've had your whole 3D life and just weren't aware of it. Sort of like silverfox, who was born with a huge rock in his head instead of a brain. Only showed up in routine x-rays...
XD
Comments
From my Radeon 8500 pro.
--Scythe--
*shudders
You do not know how true that is MonsE
Personally I am looking forward to the release of CS:CZ
Personally I am looking forward to the release of CS:CZ <!--QuoteEnd--> </td></tr></table><span class='postcolor'> <!--QuoteEEnd-->
as if we didnt know already
ontopic:
i have never noticed the anti aliasing problem, so im not bothered