Some info on Det42.74 AA modes

[Xmas]

If anyone's interested:

http://www.3dcenter.org/artikel/geforcefx_aa_modi/index_english.php

 

[Bambers]

"12x" looks like 2xMS with 1.5x2 supersampling to me (a 6x mode).

You can see the dots on the FSAA program look 'dithered' which always occurs when you have a x.5 supersample.

 

[sonix666]

Now that I have a Radeon 9700 for some days I simply don't understand nVidia. Why do they have the 4x mode which is an order grid and a 4xS mode, which is a skewed (rotated) grid BUT with two texture samples per pixel. Why don't they have a skewed version for pure multisampling?

After seeing 4xFSAA on my old Geforce 3 and on my brand new Radeon 9700 the latter with its rotated grid is simply much better visually.

 

[Mintmaster]

Now that I have a Radeon 9700 for some days I simply don't understand nVidia. Why do they have the 4x mode which is an order grid and a 4xS mode, which is a skewed (rotated) grid BUT with two texture samples per pixel. Why don't they have a skewed version for pure multisampling?

This way they don't need dedicated hardware to handle offset sample positions. Rotated 2x MSAA just uses two corners of the ordered grid from 4x multisampling. 4xS uses this 2x MSAA to create an image that is twice as tall vertically, then squishes it back to regular size by blending. That's why 4xS is not rotated, but skewed, as you correctly observed.

If you look at the 4xS sample positions in the link above, draw a horizontal line across the middle of the pixel box. Then stretch it by a factor of two vertically. You will now have two squares of the 2xMSAA sample pattern.

 

[sonix666]

Aha, thanks for the very clear explaination.