FiringSquad: Is there anything in DirectX 10 that you couldn't do in DirectX 9.0?

Tim Sweeney: Realistically, DirectX 10 doesn't introduce fundamentally new capabilities, but brings many new features that will enable developers to optimize games more thoroughly and thus deliver incrementally better visuals and better frame rates.

If you look at the long-term graphics roadmap, there have only been a few points where we've gained fundamentally new capabilities. The most visible was the move from DirectX 6, 7 and 8, which in practice were fixed-function, 8-bit rendering APIs, to DirectX 9 with programmable shaders and support for high-precision arithmetic. Most of the in-between steps have brought welcome but incremental improvements, and DirectX 10 falls into that category.

From here on, there is really only one major step remaining in the evolution of graphics hardware, and that's the eventual unification of CPU and GPU architectures into uniform hardware capable of supporting both efficiently. After that, the next 20 years of evolution in computing will just bring additional performance.

FiringSquad: Based on what you've seen with DirectX 10, do you think it will be easier for game developers to program for than DirectX 9 was? If yes, which features really stand out?

Tim Sweeney: You can't really use the word "easier" in conjunction with supporting DirectX 10. Because it's only available on Windows Vista and not XP, all developers who support it will have to continue supporting DirectX9, and henceforth maintain two versions of the rendering code in their engine. It's worth doing this, and we're doing it for Unreal Engine 3. But, far from making our lives easier, it brings a considerable amount of additional development cost and overhead to PC game development.

FiringSquad: We know that Unreal Engine 3 was largely developed with shader model 3.0 in mind, but do you plan on adding any DirectX 10 aspects into Unreal Engine 3 and ultimately Unreal Tournament 2007 or is that coming in UE4?

Tim Sweeney: Unreal Engine 3 will make full use of DirectX 10, and many of our and our partners' games will ship in 2007 with full support for DirectX 10 and Windows Vista. But, despite the marketing hype, DirectX 10 isn't all that different from DirectX 9, so you'll mainly see performance benefits on DirectX 10 rather than striking visual differences.