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http://www.beyond3d.com/forum/viewtopic.php?p=142176#142176
Forbidden Donut posted the following:
I sent sireric a PM asking if ATI was aware of this issue and what possible solutions would be. This is what he said.
[Quote, SirEric of ATI said]
It's not a special mode of AA. It has to do with the method used to sample textures. If you render a partial pixel, you need to sample the texture at that pixel to get a color for the fragment. What texture coordinate do you use for a partially covered pixel? You can use the pixel center (which is what is done in current drivers/specs), or, the R3xx allows you to sample at the centroid of the fragment.
Both systems have problems. Center of pixel can lead to sampling outside the texture, and then the application has to create a buffer region outside to compensate (but that buffer region can be unlimited, depending on the pixel/texel ratio). If you use centroid, you avoid that problem, but can create new ones in cases where you only want to sample a texel once (i.e. menus and text). We would need to way to allow the application to specify the kind of sampling wanted on each texture. That's not in the API now. However, the HW can do it. We might be able to do something in the control panel.
[End Quote]
My own personal interpretation after hearing from both sireric and the people down at valve is that there's a very strong chance that FSAA is able to be done on ATI's hardware. I suppose only time will tell what happens though.
Forbidden Donut posted the following:
I sent sireric a PM asking if ATI was aware of this issue and what possible solutions would be. This is what he said.
[Quote, SirEric of ATI said]
It's not a special mode of AA. It has to do with the method used to sample textures. If you render a partial pixel, you need to sample the texture at that pixel to get a color for the fragment. What texture coordinate do you use for a partially covered pixel? You can use the pixel center (which is what is done in current drivers/specs), or, the R3xx allows you to sample at the centroid of the fragment.
Both systems have problems. Center of pixel can lead to sampling outside the texture, and then the application has to create a buffer region outside to compensate (but that buffer region can be unlimited, depending on the pixel/texel ratio). If you use centroid, you avoid that problem, but can create new ones in cases where you only want to sample a texel once (i.e. menus and text). We would need to way to allow the application to specify the kind of sampling wanted on each texture. That's not in the API now. However, the HW can do it. We might be able to do something in the control panel.
[End Quote]
My own personal interpretation after hearing from both sireric and the people down at valve is that there's a very strong chance that FSAA is able to be done on ATI's hardware. I suppose only time will tell what happens though.
[Posted by: BRiT | Date: 07/18/03 06:09:09 PM]
