Ati Crossfire capable of 14X FSAA

[Demirug]

Yes, if it is setup properly. You send all the same data to both cards and just have differing sampling positions. Can even end up being a 'cheap' way to antialias render-to-texture targets (though there is a small chance that it might break with some titles that assume sampling positions with RTT).

Well, I suppose that is a good point. It will be more efficient at RTT, but you're still paying the cost of supersampling for something that we typically do with multisampling these days at a much lower performance hit. I still think that two cards + multisampling (with no shared FSAA) would give better performance, if an equivalent multisampling mode was available.

Yes, MSAA should always faster as SSAA.

If I want antialias RTT I can do this with MSAA, too. The DX 9.0c API contains a solution for this.

I still unsure how well this 2 chip SSAA will work if the game use a fullscreen postfilter effect.

 

[trinibwoy]

I still think that two cards + multisampling (with no shared FSAA) would give better performance, if an equivalent multisampling mode was available.

Big if.

 

[no-X]

No, because if you use the same texture LOD but use different texture coordinates, you will get similar performance to just one card doing the rendering. This will have the effect of reducing texture aliasing, but at the cost of some texture clarity. It's rather silly to waste that extra processing, if you ask me.

ATi will IMHO adjust texture LOD (ATi already made it for DX8 Radeon series - Catalyst 4.1 or 4.2 change, comparision)

SS is very good solution for aliasing on alpha textures and it offers very nice textures with adjusted texture LOD (screenshot with RGSS 8x enabled and no AF of course)

Other advantage is customizable sample positions, which can not be easily adjusted at today's single-chip solutions... So why are you so sceptical? I know this isn't the best way to implement SS, but it will be a possibility, not a must

(sorry for my English)

 

[KimB]

ATi will IMHO adjust texture LOD (ATi already made it for DX8 Radeon series - Catalyst 4.1 or 4.2 change, comparision)

Different scenario, though. If you're using multiple cards to do the supersampling, adjusting the texture LOD has a much larger performance impact.

 

[bloodbob]

Even with multiple chips you'd get that problem too. You'd need a unified cache.

 

[Blazkowicz]

with my voodoo5 I used to set the LOD to -1.5 (or even -2 but texture aliasing comes to the play) in the drivers when using fsaa 4x. quite simple isn't it? no significant performance loss, but what a great image quality (basically like good anistropic filtering)

for 2x I only used LOD -0.75 ; and -0.25 with nothing (but with mipmap dithering), as the default LOD is slightly too "high".

 

[Ailuros]

with my voodoo5 I used to set the LOD to -1.5 (or even -2 but texture aliasing comes to the play) in the drivers when using fsaa 4x. quite simple isn't it? no significant performance loss, but what a great image quality (basically like good anistropic filtering)

for 2x I only used LOD -0.75 ; and -0.25 with nothing (but with mipmap dithering), as the default LOD is slightly too "high".

VSA-100 had quite conservative LOD adjustments to start with.

Apart from that usually with Supersampling you can notice a LOD offset of -0.5 for 2x samples, -1.0 for 4x, -2.0 for 16x etc.

Beyond that whether you'll use AA or not, using LOD values below default "0" will impact performance and gradually introduce more and more side-effects on all accelerators.

Different scenario, though. If you're using multiple cards to do the supersampling, adjusting the texture LOD has a much larger performance impact.

I wonder whether they actually need a LOD adjustment after all.

 

[no-X]

Even with multiple chips you'd get that problem too. You'd need a unified cache.

And what about VSA100-based systems? There isn't this problem (and performance hit is about 5%, as I remember). I'll try to find some info about CAE tropos or ES simFusion 6x00...

edit: Blazkowicz_: that's what I'm speaking about, I have the same experience

 

[Ailuros]

Even with multiple chips you'd get that problem too. You'd need a unified cache.

And what about VSA100-based systems? There isn't this problem (and performance hit is about 5%, as I remember). I'll try to find some info about CAE tropos or ES simFusion 6x00...

edit: Blazkowicz_: that's what I'm speaking about, I have the same experience

There are 3 detailed articles here on B3D about how the T-buffer exactly works on VSA-100. Way too many differences.

 

[Cowboy X]

because I think you'll find that the most fervent ATI supporters think using dual cards is absolutely stupid and pointless

Which may well change once ATI's multi-card solution is announced and available.

I was going to say the same thing .

 

[Xmas]

There are 3 detailed articles here on B3D about how the T-buffer exactly works on VSA-100. Way too many differences.

The only relevant difference that's related to "how the T-buffer works" here is that each chip can output two samples, so with 2xAA you still have your "unified cache". The other differences are in the TMU, VSA-100 is not quad-based and likely has a different caching strategy.

 

[Unknown Soldier]

Chalnoth, ever consider that Dave has probably seen this thing in action and knows for a fact that performance is not lower in this mode?

Well, that statement has about the same merit as:

"Chalnoth, ever consider that Dave has probably seen the pigs, and the fact that they can fly?"

And the simple answer is no, it's just not possible. Depending on the settings used, the performance hit may be small, but it is not going to be zero.

You don't mind if I quote you

 

[Deleted member 2197]

http://www.hothardware.com/viewarticle.cfm?articleid=689&page=3#update

Dave Altavilla states:

We tried to duplicate the screen shots that ATI supplied to us, and found that ATI seems to have misrepresented the micro-geometry detail of NVIDIA's 8X anti-aliasing method. The screen shots we took on our own with a GeForce 6800 GT, clearly show more detail than the screen shots distributed by ATI in their CrossFire presentation. Take a look for yourself...

We wandered around the same portion of the map ATI used for their screen shots at various resolutions with a GeForce 6800 GT installed into our test system and HL2 configured for high detail, and could not replicate ATI's screen shots. Even at lower resolutions, the same portions of the antenna atop the hotel shown in the CrossFire 14X AA screen shot are visible on the GeForce. And with the resolution turned up to 1600x1200, the detail only got better. We even tried to move towards and away from the hotel from different angles and couldn't get the portions or the antennas missing in ATI's screen shots to disappear.

So, while ATI's new 14X AA method enabled by CrossFire may provide more micro-detail than other AA methods that use fewer samples, which seems evident in the edge details on the hotel sign, the difference between NVIDIA's 8X AA and CrossFire's 14X AA as demonstrated by ATI don't seem to be indicative of actual in-game images when comparable detail settings are used.

Finally, we contacted ATi for comment on this issue that we discovered and they agreed they too could not reproduce the lack of detail that is represented in the NVIDIA screen shot they provided us above, although they assured there was no intention of misleading us with these competitive image quality comparisons. This isn't the first and probably won't be the last time we will be witness to over-zealous marketing efforts, whether accidental or intentional.

Hmm ....

 

[Acert93]

Dave Altavilla states:ATI screws up big time and gets caught red handed blah blah blah

Hmm ....

Yep, exactly why I look for 2 or 3 reviews on every product. I also get a little smirk when comparing benchmarks, same game, similar systems, slightly different choice in drivers (sometimes now), and how different benchmarkers get different results and have totally different conclusions.

As for the multi-gpu thing... meh. If I had money to burn maybe... but when you look at the cost of a beefed up PSU, new MB, multiple GPUs (that already run well over $300 each), heat issues, driver support, etc... I just do not get it.

I guess I am happier just getting a new GPU every 2 years. I would rather get new FEATURES than just the same features and a faster card on old technology. But if you have cash to burn... after you get your SLI/AMR/MVP or whatever mail me some

 

[incurable]

Just imagine the ruckus that would happen here had nVidia done similar a "mistake" ...

... and yet still, some people wonder why these fora are perceived as ATi fanboi territory by outsiders.

 

[MY80S]

Hmm, I'm not really familiar with nvidia's >4xAA modes but, are they (supposed to be) comparing SuperAA to 4xMS*2xSS or 2xMS*4xSS ?

 

[trinibwoy]

Hmm, I'm not really familiar with nvidia's >4xAA modes but, are they (supposed to be) comparing SuperAA to 4xMS*2xSS or 2xMS*4xSS ?

They have both.

 

[KimB]

I'm reasonably certain that you can't expose the 4xMS * 2xSS mode without a tweak program, though (at least, it was this way early-on....I haven't played around with these half-supersampling modes).

 

[Randell]

Correct, but the nHancer program makes setting up game profiles so easy (easier than via the nvidia control panel!), its silly not to use them where useful

 

[digitalwanderer]

Correct, but the nHancer program makes setting up game profiles so easy (easier than via the nvidia control panel!), its silly not to use them where useful

I'll vouch for nHancer in a heartbeat, it's now my proggy-o-choice for nVidia tweakage and an important tool in me geek arsenal.

It's profiles are pretty nice and a LOT better than nVidia's profile system, but I still think Radlinker has got the best per-game profile set-up around. (You just right click on the game icon and choose "Custom Options" and then have full control over all the D3D/openGL settings when you right-click on it next time.....heaven! )

But nHancer is a great program and should be included with every nVidia card sold. (Same as Radlinker should be included with every ATi card)