Now that the regular tests are done it’s time to focus on the main new feature of the GeForce 185.20 beta driver, the support for Ambient Occlusion. According to Wikipedia, ambient occlusion is "a shading method used in 3D computer graphics which helps add realism to local reflection models by taking into account attenuation of light due to occlusion" while, according to Nvidia, it is "a lighting model that approximates the amount of light reaching a point on a diffuse surface based on its directly visible occluders."
Put very simple by the guys at Criterion Games (the developers of the Burnout series), ambient occlusion is "an effect that uses soft shadows to add extra depth" to a scene. Basically, every object in the world is lit by one or more sources in the environment but the degree of visibility of certain areas depends on shape, orientation in regards to the light source(s) and other objects that may block or lower the amount of light that reaches those areas. Calculating all the twists and turns of the light will lead to soft shadow "models" which, once applied, will provide more depth to objects and characters, and make for a more realistic game scene. Ah, but haven’t we heard about "more realism" way too many times to get excited? We have, so it's best to play it safe and first see the difference brought by enabling ambient occlusion with the GeForce 185.20. The lab rats for this experiment are Crysis Warhead and the Cryostasis: Sleep of Reason TechDemo.
With ambient occlusion set to 'High' via the Nvidia Control Panel, Crysis Warhead really gets 'transformed' with the most obvious and significant differences being seen at the fence on the right and the trees. The tree line is definitely darker and, as debatable as it might be, it does have an added depth.
In the example above we can again see the vegetation getting a good dose of 'dark' from enabling ambient occlusion, and while it may be a bit too much, it's still better than the somewhat faded render made without AO. In all, AO does have a very noticeable visual impact on the game but that's just half the story as performance is also impacted.
The colored bars say it straight - enabling Ambient Occlusion (and setting it on high) leads to a FPS drop which, in our case, was of almost 7 FPS on average. The FPS counter went below 9 with AO and that, coupled with the 17 FPS on average and the maximum of 22.63 FPS, make for an unacceptable scenario for a first-person shooter. Moving on to Cryostasis…
… we see that the sub-zero first-person shooter also puts ambient occlusion to good use and, as opposed to Crysis Warhead, provides an glimpse at what ambient occlusion can do in-doors. Enabling AO results in a more vivid environment with brighter lighting and shadows, more intense red lights and a fan that has, yes, added depth.
This last 'before and after' scene is nothing short of relevant as to the visual improvements brought on by ambient occlusion. The picture is simply livelier, sharper, better contrasted, with several areas (the zone of the floor to the left of the running tube) being more appropriately lit and the water being more visible.
Enabling AO led to a greater framerate drop in Cryostasis than it did in Crysis Warhead, with the average FPS count, as depicted in the chart above, going down close to 50% (47.1% to be exact). That's a pretty high price for extra eye-candy.
From everything seen here we can pretty much say that ambient occlusion is a nice addition to the GeForce 185.20 beta but for now, it's only a temporary play thing. AO surely brings noteworthy visual improvements in games but it also has a big impact on performance and that limits its use. Still, given the fact that ambient occlusion hasn’t even been introduced in any official beta or WHQL driver, we can hope that future GeForce 180 series releases will include AO optimizations to lower its impact. All right, time to wrap up.
Page 01: Introduction
Page 02: Test setup
Page 03: 3DMark06
Page 04: 3DMark Vantage
Page 05: Devil May Cry 4
Page 06: Unreal Tournament III
Page 07: Half-Life 2: Episode Two
Page 08: Crysis Warhead
Page 09: Far Cry 2
Page 10: Call of Duty: World at War
Page 11: Cryostasis: Sleep of Reason
Page 12: Ambient Occlusion - visual and performance impact
Page 13: Conclusion
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