On modern Radeon graphics cards Screen Space Ambient Occlusion (SSAO) works only if anti-aliasing (MSAA) is deactivated - current Geforces on the other hand display both effects at the same time.
Empire Total War: SSAO plus MSAA nur auf Geforces möglich [Source: view picture gallery]
The Warscape Engine of Empire: Total War supports Screen Space Ambient Occlusion (SSAO). For this the engine calculates additional or variable shadows in dependence to the reflections of the light with simultaneous consideration of shadows that exist already. The result is a noticeably illuminated scene, but unsurprisingly SSAO costs a lot of performance: In the test the framerate delivered by a Radeon HD 4870/1G was lowered from 51 to 30 fps by SSAO.
During our tests we noticed that it is not possible to run anti-aliasing (MSAA) at the same time as SSAO on current AMD graphics cards (Radeon HD 3000 and HD 4000) - you have to choose one of the effects. Unfortunately neither of the options is disabled in the video settings of the game, so that inexperienced users might not notice that only one option is active. Current Geforces (Geforce 8/9 and GTX 200) on the other hand can display MSAA and SSAO simultaneously and thus offer the noticeably better visual quality in Empire: Total War as the comparative picture below reveals.
We already contacted AMD about the matter and they are investigating the problem. It's quite strange though since in HAWX and Burnout Paradise the combination of MSAA and SSAO is working properly on Radeon cards. Therefore we estimate that the problem is related to Empire rather than AMD.
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