aa quality on 6800 and x800?

[wonky_ewok]

Dear all,

I'm trying to decide between an x800 pro and the 6800gt. Image quality is very important to me, especially 'jaggies'. When I want to be immersed in a 3d world, I want to be immersed!

I was heading for the x800, but I came across this:

http://www.firingsquad.com/hardware/geforce_6800_performance_and_overclocking/page3.asp

which shows some bad jaggies (on the runway) for the X800. Could any one tell me if it's still accurate (newer drivers). and if so is it representative? Are there any generally noticeable differences between 6800 4x and X800 4x aa?

I've seen some comparisons of 6800 8x and X800 6x on a bigger range of scenes (from another thread here), and I think the NV8x is better, but it's too slow from what I read.

Thanks.

 

[hovz]

ati doesnt apply aa to textures.

 

[BRiT]

More correctly, multi-sampling anti-aliasing (MSAA) technique does not apply anti-aliasing to alpha-textures.

Nvidia's 8x mode is a combination of MSAA and super-sampling anti-aliasing (SSAA). The SSAA mode is what causes the drastic drop in performance.

ATI uses MSAA and does not offer SSAA on the PC. They do offer some SSAA modes on the MAC.

 

[Dave Baumann]

ati doesnt apply aa to textures.

All MSAA techniques apply AA to textures at polygon edges.

 

[hovz]

i think what i said was pretty clear.

 

[darkblu]

ati doesnt apply aa to textures.

All MSAA techniques apply AA to textures at polygon edges.

all generalizations are bad (tm) 8)

 

[wonky_ewok]

Please bear with me while I'm learning

Is it then AF which (effectively) smooths the interiors of the 'alpha textures', and
Are you implying that those jaggies were from within the textures, rather than being polygon edges?

In which case I should be fussed about AF not (or not only) AA?

Thanks!

 

[jvd]

If you want image quality go with a x800xt plat . 90% of the time I can run with 6x fsaa or temporal 6x . 4x temporal is almost allways usable .

It works wonders

the 6800gt clocked to ultra extreme speeds has 8x fsaa playable about 60% of the time .

if you look at what ante p said and others in that thread the image quality between 6xfsaa and 8xfsaa is almost the same , sometimes 6x is better sometimes 8x is better

 

[Cryect]

Please bear with me while I'm learning

Is it then AF which (effectively) smooths the interiors of the 'alpha textures', and
Are you implying that those jaggies were from within the textures, rather than being polygon edges?

In which case I should be fussed about AF not (or not only) AA?

Thanks!

Alright AF is essentially for situations where the texture has been "smoothed" too much due to applying a higher mipmap level than is needed. Basically AF is trying to sharpen the texture detail that is loss due to mipmaps at sharp angles (mipmaps are designed for the situation where polygons are perpendicular for the screen).

But for jaggies what you want is AA. The problem for alpha textures is MSAA looks for the edges of a polygon and then says we need to have a higher resolution here. Now if an alpha texture is using a alpha test of greater than instead of an alpha blend (as often is done with plants and such) the result is a jagged looking edge that can't be fixed by MSAA since it doesn't consider that an edge. Now it would be nice if one of the card vendors adds another mode similar to MSAA for alpha textures under those particular alpha tests it would then mark it as edge and raise the resolution appropriately.

 

[Lecram25]

*confused*

I was definately under the impression that the MSAA and SSAA mixed mode was for 8x only, and that nVidia uses /pure/ MSAA for their 4xAA implementation.

I'd just like to know how and why they're able to AA the runway textures when the firingsquad used 4xAA. Unless it's a huge typo of course.

Screen shots:

x800

6800


And of course the original link.

 

[Pete]

6800 offers MSAA at 2x and 4x, and a mixed MS + SS AA mode for 8x (initially 4xSS + 2xMS, now 2xSS + 4xMS--for performance reasons).

Those shots were discussed in a previous thread, but I don't know if the reason for ATi's more "aliased" runway was ever established. The runway's features are probably due to textures, not polygons, so we can rule out the 4x AA used in both screenshots as the culprit. That leaves either the difference in gamma or nV's superior texture interpolation, AFAIK.

If Brandon hasn't commented as to whether he's investigated further into the IQ differences, maybe he can do so now? If he has, can someone please provide a link? TIA.

 

[KimB]

I've been complaining that ATI's had more texture aliasing for quite some time now. This is a prime example of that.