We held a Clinic on DirectX Gaming in early December, which gave me a reason to play several of the recent demos as well as full versions of several new game titles. I was trying to identify differences one might find between playing your game under Windows XP (DirectX 9) or under Vista with and without DirectX 10 compatible video.

There is a whole set of features that is available to programmers who wish to exploit the features supported by the DirectX 10 command set when using compatible hardware and OS. If you are not already aware, DirectX 10 is currently only available under Windows Vista, and then, only if you have a video card that supports the instruction set. Currently, that includes the NVIDIA GeForce 8xxx series and the ATI Radeon 2400, 2600, 2900 and 3800 video cards.

BioShock

Crysis

Two of the more fascinating first-person shooters I examined were Crysis and BioShock. I "forced" myself to play these games (a couple of times) to try to find out what sort of DirectX 10 support and features are currently available. Both games offer DirectX 10 support, but don't require it, meaning you can still enjoy them under Windows XP and DirectX 9.

In the Crysis game under Windows XP with DirectX 9, the video setting test sets the quality levels to "Medium" or "High" (at best), depending on the rest of your hardware configuration. On the exact same system hardware under Vista with DirectX 10 support, the video settings test should configure the game quality to "Very High."

Sunrise in Crysis: The lighting effects are subtle, but very realistic throughout the game. Time passes as you explore, and the lighting changes accordingly. These images show the same view at Medium, High and Very High quality video settings. Water reflections and shadows show the greatest differences between the settings. Remember, "Very High" is selected when DirectX 10 support is available.

In most cases, you have to specifically look for the DX10 differences, and even go so far as to compare screen shots to tell if they are really happening. For example, in BioShock DirectX 10 will be used to handle some of the lighting effects, with shadows being one of the more noticeable effects.

DirectX 9 Detail

DirectX 10 Detail

At first glance, these screenshots appear to almost identical, but a closer examination shows soft-edged shadows on the figure in the DirectX 9 image (left) and sharp-edged shadows under DirectX 10 (right). This is particularly apparent in the figure's fingers and the wheels of the carriage. Since the lighting is supposed to be a point source, the sharp-edged shadow should be the more realistic. In other settings, the shadows will be the just the opposite, displaying soft-edges from diffused lighting, or even multiple shadows created from several light sources.

The key benefit of DX10-enhanced games is not necessarily the improved graphics and visual appearance. By transferring the processing needed for lighting effects (including shadows, reflection and refraction), improved surface mapping and texture details to the video card's GPU (Graphical Processing Unit), the CPU can handle improved Artificial Intelligence (AI) functions and physics to make the game play even more realistic. In Crysis, your special nanosuit has a stealth capability, but your opponents will still react to sounds, shadows, or other hints that things are not as they (don't) appear. Your opponents will also react in a methodical way if you suddenly "disappear" by sweeping the area with gunfire or executing a structured sweep of the area. Granted, this behavior occurs in the game even under DX9, but without as much detail to the environment.

Even without DirectX 10 support, these games are stunning in their presentations and visual effects. Water effects are varied and realistic in the Art Deco world of BioShock. The vegetation, water, and human characters throughout the flash-frozen environment of Crysis are impressive, even while working under the burden of a "medium" graphics mode quality setting.

The underwater city of Rapture displays characteristic Art Deco elements in the architecture, furniture, and equipment. It also appears to be falling apart, with flooded rooms, waterfalls, and fish swimming outside the windows and skylights.

One thing for sure - the developer's efforts are obvious in the appearance and overall atmosphere of recent games. From what I can tell, DirectX 10 makes the graphical portion run smoother, faster and with better details, and probably more challenging as increased computing power becomes available to the AI controlled opposition. Nothing that can't be overcome with some handy cheat codes or trainers, all in the name of research, of course...

A brief summary of DirectX 10 can be found on the Microsoft "Games for Windows" website.

NVIDIA maintains a developer section on their website and has a series of programming samples and video clips that show the DirectX 10 feature in action. The videos are cool since you don't need Windows Vista and DX10 video to view them. Check these out at
NVIDIA's site.

Hot Hardware posted an article by Michael Lin on "The State of DirectX 10 - Image Quality and Performance" back in October of 2007. In the article he reviews five of the game demos, compares the features of DX9 and DX10 side-by-side and also includes benchmarks when running with DX9 and DX10. How meaningful these really are might be debated unless you were comparing a program version written specifically for DX10 against one written for DX9. To be backward compatible, the games would have to rely heavily on DX9 features, limiting the DX10 feature set in the process. It seems all of the benchmarks show that DirectX 9 out-performs DirectX10 in nearly every situation. Since DirectX 10 features cannot be executed in a DX9 environment, it suggests that additional activity may be taking place in DX10 hardware in addition to the DX9 graphics already being processed, usually resulting in poorer performance, not better. Check out the article at Hot Hardware.

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