Image Quality: DirectX 11 Enhancements
Hardware Tessellation: Character and Detail
In layman's terms, hardware tessellation creates extra geometry detail on simple 3D models. The best way to understand what's going on is to look at the following screenshot:
In Aliens vs. Predator, tessellation is primarily applied to the alien mesh, as shown above. I have seen documentation from AMD suggesting that there might be environmental objects that show a benefit from DirectX 11 tessellation, but I was unable to find any actual examples in-game for a screenshot.
That leaves tessellating the alien model as this feature's raison d'être, and when you look at the above comparison, you can't help but be impressed. However, in-game, the alien mesh is moving quickly and covered with a shiny texture that minimizes the impact of tessellation. More on that in a bit.
DirectX 11 High-Definition Ambient Occlusion (AO)
AO is a feature used to increase the realism of a game's lighting model. AO algorithms simulate the phenomenon where light has a hard time illuminating cracks and crowded spaces.
Aliens vs. Predator offers an AO feature in DirectX 9 mode that does a fantastic job of adding depth in some of the scenes, particularly on some foliage. In DirectX 9 mode, AO offers an unmistakable boost to the visual experience. In DirectX 11 mode, the AO feature is performed with greater definition. This is called HDAO, and the benefits over DirectX 9 AO are very subtle and hard to point out.
While it's nice that the game is delivering better AO precision, DirectX 11 AO vs. DirectX 9 AO effects are so similar that the differences are not something that I think anyone could actually notice while playing.
DirectX 11 Enhanced Shadows
DirectX 11 mode enables an “enhanced shadow” option that will deliver slightly superior shadow edges in-game. This is an extremely subtle effect and even screenshots need to be scrutinized to point out any differences.
In Aliens vs. Predator, DirectX 11 mode has one clear and unmistakable advantage: AA support. This feature is simply unavailable in DirectX 9 mode.
Since AA can be an important part of extracting the best visual experience from your hardware and monitor, there is little more to say. We are a bit puzzled and disappointed that AA isn't available in DirectX 9 mode, though.
Now, this is something we're very interested in testing for ourselves: Rebellion claims that DirectX 11 mode offers better performance despite the increase in visual fidelity. If this is true, the subtlety of the DirectX 11 effects is easily overlooked if game performance actually increases. In DiRT2, we found that DirectX 11 really hammered performance. So, it'll be interesting to see if the API has the opposite effect here.