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Old 10-14-02, 07:41 PM   #31
Chalnoth
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Join Date: Jul 2002
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Quote:
Originally posted by jbirney
Oh really then why do we keep hearing about a SS mode being availble in the R300 just disabled for now in the drivers?
Talk does not equal implementation.

Quote:
No I Understand what you ment but your wording in not correct. If you wrote a very adaptive edge detection algorithm then even in x2 mode you could have a sample point inside the edge and detect it. However thats not the point here. We are taking about a method that NEVER will when Alpha test is used vers a method that fails only under certin conditions...
Um, when an alpha-tested texture displayed doesn't count as "certain conditions?"

Basically, there are some scenes that will always show some edge AA for every single edge with 4x+ MSAA enabled, and some scenes where certain edges will always show no AA.

For 2x SSAA, in almost every single complex scene, there will always be some edges that will show no AA.

To say that MSAA always fails seems to be assuming that every single edge that is displayed is on an alpha-tested texture. That's just ludicrous.

Quote:
But back to the point you do realize that its the same AF method they used back in the R8500 just with an tweak to handle angles better. Thus its a perfromnace tweak as ATI themselves have stated.....
It's not a performance tweak, not in the least.

Quite simply, just as you've stated yourself (but in other words), the percent of the screen in most FPS situations that has reduced degrees of anisotropic is just too small to make for any significant performance benefit.

Therefore, the only possible performance discrepancy can come from the calculation of the anisotropic degree, which will vary between different methods. Still, it is more than possible to have hardware that calculates anisotropic in any possible way once per clock per texture pipeline.

This makes it solely a transistor count optimization.

Update:
One final thing on the personal attacks. I was merely stating that if your background had as much bearing on this situation as you thought it did, then you would agree with me on the point I made above. It's not very hard to figure out.

Oh, one final final thing. I never have said that ATI's anisotropic was broken, a hack, or a cheat. I'm just saying that it seems silly to me that ATI has yet to implement a good degree-selection algorithm, especially now with a 100+ million transistor product that supports the exact same number of transistors as their previous product.

As a side note, however, it appears that the 8500->9700 implementation change would take exactly twice the computational power in selecting the degree of anisotropic. This means, to me, that ATI's drop to one texture per pixel pipeline probably didn't affect the anisotropic degree selection hardware hardly at all. That is, there's still enough hardware to select two anisotropic degrees per pixel pipeline, but they are now combined to support a somewhat better algorithm. It really, really seems to me like doing the proper aniso degree selection (which something along the lines of sqrt(x^2 + y^2), as opposed to the absolute values that ATI apparently uses) would be very close to the same expense in transistors.

Last edited by Chalnoth; 10-14-02 at 07:53 PM.
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