DiRT 2 Demo DX11 Performance and IQ Preview

What are some new DX11 features DiRT 2 Demo brings with it, and what do they look like? Will DX11 cause a large drain on performance? These topics are briefly previewed today with the DiRT 2 demo and a handful of video cards.


DiRT 2 is the sequel to 2007’s Colin McRae: DiRT from Codemasters. DiRT launched for consoles in September, but launches for Windows on December 8. DiRT is a racing game which celebrates off-road racing of all types, including Rally races, the Baja, Trophy Trucks, and many others. Originally named Colin McRae: DiRT 2, it is the first game bearing his name since the Scottish driver’s death by helicopter crash in late 2007.

The console versions of DiRT 2 were well-received, garnering high marks from game critics and an aggregate score of 87/100 on metacritic.

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DiRT 2 Demo

DiRT 2 is coming to the PC late, approximately three months after the console release. However, the PC version contains some features unavailable on the Xbox 360 and PlayStation 3, namely DirectX 11 support. DiRT 2 supports such DX11 features as hardware tessellation, High Definition Ambient Occlusion (HDAO), 64-bit (R16G16B16A16) HDR lighting, and full screen resolution post-processing. The hardware tessellation is executed on water, crowds, and cloth. HDAO is used to improve the depth and appearance of ambient lighting models by simulating the occlusion of ambient lighting by object surfaces. The 64-bit HDR is used to create smoother HDR lighting effects, which has a very noticeable effect on large display devices.

This article is not intended to be a conclusive look at DiRT 2. Rather, it is a look at the game’s demo, which features two venues and races from the complete game. The data and imagery collected for this article reflects the demo only, and does not necessarily reflect the quality of the complete game. We do have a complete evaluation of the complete game on the way in the coming weeks. For now, this article should give you a basic idea of what DX11 brings to DiRT 2 over DX9, and what kind of performance you may reasonably expect.

Screenshot Comparisons

In the demo, the available examples of hardware tessellation were too few to effectively communicate the advantages tessellation offers. Look to our full evaluation of the full game for examples and breakdown of that technology. In this preview, we are going to focus on the three features that made the biggest difference between DX9 and DX11 rendering: High Definition Ambient Occlusion, 64-bit HDR, and improved shadow rendering. The screenshot comparisons below show these features.

HDAO - High Definition Ambient Occlusion

HDAO is a DirectCompute accelerated algorithm for shading low points of objects. HDAO is an expensive system, in terms of the computing power required, because it needs to sample the depth buffer repeatedly. Using DirectCompute, which is a new component of DirectX 11, DiRT 2 accelerates the HDAO algorithm by reducing the overall calls to the renderer’s texture buffers.

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The first screenshot above is shown in DirectX 11, and the second screenshot shows DirectX 9 (the only other API supported in this game.) In the first screenshot, notice the shadow on the locker behind the blonde woman in the center of the screenshot. Also, notice the shadows around the drawers and handles of the toolbox on the right side of the image. In the second image, the woman’s shadow is gone, and the shading of the toolbox is less detailed.

64-bit HDR

HDR is a lighting technique that is familiar to most gamers, but 64-bit HDR is something new. In DirectX 9, the standard HDR model is 32-bits, or 8 bits per channel (R8G8B8A8). DirectX 11 supports HDR with 16 bits per channel (R16G16B16A16), which creates smoother, more accurate bloom lighting effects.

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In the first image above, notice the soft shading around the men in the blue and purple clothing on the left side of the image. In the right side, under DX9, that lighting is gone and the scene looks quite a bit more flat. Here, HDR is being used to enhance depth.

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In the first image above, the lighting bloom around the trailer window is warm and rich, like real sunlight. It lends an overall warm tone to the entire scene. In the second shot, the HDR effect is not as intense and not as warm.

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The blue sky in the first image above blends smoothly with the bright golden sun. The 64-bit HDR processing ensures that the change in color is smooth and subtle. In the second image, there is slight evidence of banding, as the overall blending of colors is not as smooth.


The shadows in DiRT 2 are, to be frank, a lot better under DX11 than under DX9. While this change was not as hyped in the information we received from AMD about the game, it was the most noticeable improvement for us. Thus, there were a lot more visible examples.

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In the first image above, the shadow cast on the aluminum siding of the trailer is very smooth. In addition, the handle of the small compartment in the lower left side of the image casts a shadow on the compartment door. In the right hand image, the shadow on the side of the trailer is very strange. It has a pixilated and rough appearance. Also, the compartment door handle is not casting a shadow.

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This comparison shows similar effects. The shadows on the side of the truck, and on the seat of the folding chair on the right are very smooth, and the compartment handles cast shadows. In the second picture, shadows on the chair and on the side of the truck are rough and uneven, and the little handles cast no shadows.

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In the DX11 image above, we see two problems. The first problem is with the shadows of the spoiler. We can see that the shadows of the spoiler supports do not actually touch the supports. Second, we can see that there is some shading on the roof of the car on the right side of the intake structure. It looks as though it is supposed to be a shadow of the intake, but it doesn’t really match the structure, and it looks uneven and rough. Under DX9, however, it isn’t really better. The strange shadow on the top of the car is gone, and the shadow of the spoiler looks even worse. It wasn’t perfect in DX11, but it was at least smooth. In DX9, the shadow is way off, and it has the same uneven, pixilated appearance we observed earlier.

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In the DirectX 11 image above, we can see several shadow improvements at work. First, there is the cooling fan assembly. In DirectX 11, all of the roll-cage pipes and other structures cast shadows on the cooling fans. In DirectX 9, those shadows are mostly gone. Under DX11, there is a shadow cast by the strap into the spare wheel, and under DX9, that shadow is gone. In DX9, we can see some shadow precision errors on the ground on the right edge of the image, where the shadow doesn’t quite touch the edge of the tire and fender. In DX11, that problem does not appear.

We know, you guys really want to see some tessellation comparison screenshots, and we will dive into that specific technology in the full evaluation.

Video Cards

As this article is a quick look at a demo of a game, we have a limited selection of video cards for you. We wanted to show you the best single-GPU video card from NVIDIA and from AMD, and then some more affordable options.

So, from AMD we have the ATI Radeon HD 5870 and Radeon HD 5850. From NVIDIA, the GeForce GTX 285 and GTX 275 are represented. We will, of course, have a full spectrum of video cards for the future gameplay performance and IQ evaluation of the full retail version of DiRT 2.