Real World DirectX 10 Performance: It Ain't Pretty

Call of Juarez

There has been quite a bit of controversy and drama surrounding the journey of Call of Juarez from DirectX 9 to DirectX 10. As many may remember, AMD handed out demos of the DirectX 10 version of Call of Juarez prior to the launch of R600. This build didn't fully support NVIDIA hardware, so many review sites opted not to test it. On its own, this is certainly fine and no cause for worry. It's only normal to expect a company to want to show off something cool running on their hardware even if it isn't as fully functional as the final product will be.

But, after NVIDIA found out about this, they set out to help Techland bring their demo up to par and get it to run properly on G80 based systems. Some publications were able to get an updated build of the game from Techland which included NVIDIA's fixes. When we requested the same from them, they declined to provide us with this updated code. They cited the fact that they would be releasing a finalized benchmark in the near future. Again, this was fine with us and nothing out of the ordinary. We would have liked to get our hands on the NVIDIA update, but it's Techland's code and they can do what they want with it.

Move forward to the release of the of the Call of Juarez benchmark we currently have for testing, and now we have a more interesting situation on our hands. Techland decided to implement something they call "HDR Correct" antialiasing. This feature is designed to properly blend polygon edges in cases with very high contrast due to HDR lighting. Using a straight average or even a "gamma corrected" blend of MSAA samples can result in artifacts in extreme cases when paired with HDR.



The real caveat here is that doing HDR correct AA requires custom MSAA resolve. AMD hardware must always necessarily perform AA resolves in the shader hardware (as the R/RV6xx line lack dedicated MSAA resolve hardware in their render backends), so this isn't a big deal for them. NVIDIA's MSAA hardware, on the other hand, is bypassed. The ability of DX10 to allow individual MSAA samples to be read back is used to perform the custom AA resolve work. This incurs quite a large performance hit for what NVIDIA says is little to no image quality gain. Unfortunately, we are unable to compare the two methods ourselves, as we don't have the version of the benchmark that actually ran using NVIDIA's MSAA hardware.

NVIDIA also tells us that some code was altered in Call of Juarez's parallax occlusion mapping shader that does nothing but degrade the performance of this shader on NVIDIA hardware. Again, we are unable to verify this claim ourselves. There are also other minor changes that NVIDIA feels unnecessarily paint AMD hardware in a better light than the previous version of the benchmark.

But Techland's response to all of this is that game developers are the one's who have the final say in what happens with their code. This is definitely a good thing, and we generally expect developers to want to deliver the best experience possible to their users. We certainly can't argue with this sentiment. But whether or not anything is going on under the surface, it's very clear that Techland and NVIDIA are having some relationship issues.

No matter what's really going on, it's better for the gamer if hardware designers and software developers are all able to work closely together to design high quality games that deliver a consistent experience to the end user. We want to see all of this as just an unfortunate series of miscommunications. And no matter what the reason, we are here today with what Techland has given us. The performance of their code as it is written is the only thing that really matters, as that is what gamers will experience. We will leave all other speculation in the hands of the reader.

So, what are the important DirectX 10 features that this benchmark uses? We see geometry shaders to simulate water particle effects, alpha-to-coverage for smooth leaf and grass edges, and custom MSAA resolve for HDR correct AA.



Call of Juarez Performance


The AMD Radeon HD 2900 XT clearly outperforms the GeForce 8800 GTS here. At the low end, none of our cards are playable under any option the Call of Juarez benchmark presents. While all the numbers shown here are with large shadow maps and high quality shadows, even without these features, the 2400 XT only posted about 10 fps at 1024x768. We didn't bother to test it against the rest of our cards because it just couldn't stack up.



Call of Juarez 4xAA Performance

With 4xAA enabled, our low-end NVIDIA hardware really tanks. Remember that even these cards must resolve all MSAA samples in their shader hardware. AMD's parts are designed to always handle AA in this manner, but NVIDIA's parts only support the feature inasmuch as DX10 requires it.

We do see some strange numbers from the low-end NVIDIA cards at 1600x1200, but its likely that they performed so poorly here that rendering certain aspects of the scene failed to the point of improving performance (in other words, it's likely not everything was rendered properly even though we didn't notice anything).