Image Quality: DirectX 11 Vs. DirectX 9
Before I say anything else, I'm going to mention the experience I had in evaluating DiRT 2's DirectX 11 implementation: it turns out that people see what they expect to see. I'm as guilty of this as anyone, which is why we collect objective data like screenshots to support any conclusions we make. Despite the proof, you would not believe how many people have accused me of making a mistake when comparing DiRT 2's DirectX 9 and DirectX 11 visuals. Some folks assume that the difference is huge, and the mind tends to play tricks to convince its owner that expectations will be met. I've had discussions with readers claiming that the difference between DirectX 9 and DirectX 11 in DiRT 2 is like night and day, that it's incredibly obvious to them, and if the evidence doesn't support that opinion, then the evidence must be flawed. But the evidence shows that the differences are minor at best, and completely unnoticeable during gameplay at worst.
Why am I mentioning this? It's a pre-emptive strike, because Aliens vs. Predator falls in the same boat. Folks, it is almost impossible to tell if this game is running in DirectX 9 or DirectX 11 mode during actual play. Despite the impressive tessellated alien mesh on the previous page, I am convinced that there is no realistic way to tell if the game is running in DirectX 9 or 11 mode while playing it unless AA is enabled, assuming your style of gameplay doesn't involve spending time standing still and staring at alien corpses until they melt away.
While the potential for tessellation to improve the detail of a 3D model is undeniable, any noticeable increase in the final result depends on the difference between the appearance of the standard version vs. the tessellated version. The standard alien model is extremely well-detailed, and so meticulously crafted, in fact, that I don't think it's at all practical to assume anyone would see the difference while playing this game. Perhaps a player might notice something if they scrutinize a non-moving alien body, but while actually playing the game and fighting the aliens, it's completely unapparent.
What about high dynamic-range AO and DirectX 11-enhanced shadows? These features are even subtler than the tessellation effect. In a static screenshot comparison, you need to struggle to find any difference whatsoever.
The only DirectX 11-exclusive feature with noticeable teeth is AA, which is no surprise. I'm not sure what the technical reason is that prevents AA from running on DirectX 9 hardware, but the DiRT 2 developers managed to include AA in the DirectX 9 code path. The great majority of DirectX 9 games out there support AA, and to me the feature is important enough to spend development time on for a universal solution. In any case, none of this is the API's fault. If you want to use AA in this game, you will need a DirectX 11 graphics card. End of story.
What's the good news? In our testing, the DirectX 11 code path provided superior performance compared to DirectX 9 in many cases, even though the enhanced effects were enabled. That means that all the DirectX 11 goodness is often free, and in this light, the miniscule visual impact doesn't seem so bad. It's one thing to trade performance for tiny details, but it's quite another to have your cake and eat it, too.
Our final verdict is that this game will look fantastic with a DirectX 9 graphics card, but if you do have a Radeon HD 5000-series card in your machine, there's no reason to turn DirectX 11 features off.