Ambient Occlusion Performance

[antirobot]

Hi,

My obsession has become running Skyrim with all the eye-candy maxed at 60fps with vsync at 1080p. Right now I'm on an i5-750 (OC 4.0GHz) and a GTX 670 4GB. I moved from GTX460s in SLI and noticed certain improvements (particularly around VRAM usage on high res textures), but I still can't enable Ambient Occlusion, even on performance, without a lot of stuttering. I'm considering upgrading to Ivy Bridge and possibly adding a second 670, but I'm concerned about that not making a difference on the Ambient Occlusion issue.

I guess my real question is: what is the bottleneck for Ambient Occlusion? Would SLI make any difference? Is being CPU-bound an issue, or is Ambient Occlusion all about the GPU? Is there a GPU that can handle it? Is it specific to this game?

Any insight would be appreciated.

Thanks,
Bill

 

[Red Hawk]

I would guess that ambient occlusion is a GPU limited feature. I know that the way ambient occlusion gets implemented in AMD Gaming Evolved sponsored games is partly driven by DirectCompute, but that's probably not the case with Nvidia implemented AO. Really though, ambient occlusion in Skyrim can only be enabled through the drivers for Nvidia cards, and thus there's no guarantee that performance will ever be smooth.

 

[2is]

AO is heavily GPU dependent, so adding a 2nd GPU should help quite a bit.

 

[Pottuvoi]

Considering that Screenspace ambient occlusion schemes work by sampling depth texture several times,so the bottleneck being either TEX units and/or bandwidth.
(there might also be a bilateral upscaling pass and blurring, depending on method used.)

Nvidia control panel most likely uses this method.
Horizon Based Ambient Occlusion.

 

[BFG10K]

A CPU will do squat for AO, so don’t waste your time with IB. AO is all about the GPU, as are most graphics settings.

I personally find the feature to be useless; a massive performance hit with changes to IQ that can usually only be detected in side-by-side screenshots. It’s the first thing I turn off if I need more performance, and I never run it from the control panel either.

 

[3DVagabond]

A CPU will do squat for AO, so don’t waste your time with IB. AO is all about the GPU, as are most graphics settings.

I personally find the feature to be useless; a massive performance hit with changes to IQ that can usually only be detected in side-by-side screenshots. It’s the first thing I turn off if I need more performance, and I never run it from the control panel either.

While I find it's IQ a bit better than you, I agree 100% it's the first thing to shut off. The performance hit is dramatic. Especially if you force it in drivers.

 

[antirobot]

In some games I really like the look of ambient occlusion, but it definitely chews up performance. It sounds like unless the game developer includes it as an in-game option, it's not worth bothering with. I didn't realize there was a difference between the control panel option and an in-game setting, but it sounds like that's a pretty big factor. Thanks for the information.

 

[hans030390]

How are you enabling AO, through the Nvidia control panel or through ENB? If you're not using ENB...you should be.

 

[antirobot]

I'm enabling it through the control panel. I've tried ENB, but my performance has typically been worse using it. Do you find performance with ENB AO better than the control panel method (I would imagine it looks better). I haven't tried it recently because my results were always pretty lackluster before, but maybe performance has improved since the last version I tried?

 

[2is]

In some games I really like the look of ambient occlusion, but it definitely chews up performance. It sounds like unless the game developer includes it as an in-game option, it's not worth bothering with. I didn't realize there was a difference between the control panel option and an in-game setting, but it sounds like that's a pretty big factor. Thanks for the information.

Agreed, I personally think BC2 for example looks much better with AO. I would gladly reduce AA in favor of AO if I needed to. The problem I've found with AO is that the lower forms of it (SSAO) don't do much, but the higher forms (HBAO) make a nice difference, but unfortunately also come with a heaver performance penalty.

 

[darckhart]

i love hbao/ssao. i switch to ssao if i need more performance, but the difference in visual immersion is great.

as others have said, it's totally gpu. if it's worth another 670 is up to you...

 

[moonbogg]

This is one of those things that seem gimicky and exist for the sake of claiming another feature of the hardware. I would get real FPS numbers from people with 670SLI before spending money. If its that bad with one card, adding a second probably won't get you where you want to be.