AnandTech: Real World DirectX 10 Performance: It Ain't Pretty

Introduction

When it was drafted, DirectX 10 promised to once again change the way developers approach real-time 3D graphics programming. Not only would graphics hardware be capable of executing short custom programs (called shaders) on vertices and fragments (pixels), but developers would be able to move much more high-level polygon work to the GPU through geometry shaders. Pulling polygon level manipulation off the CPU opens up a whole host of possibilities to the developer.

With adequate performance, many of the geometric details simulated through other techniques could be applied in simple, straightforward ways involving less overhead. Techniques like normal mapping, parallax occlusion mapping, and many others exist solely for generating the illusion of additional geometry. Ever wonder why a face can be incredibly detailed while the silhouette of the same head looks more like a stop sign than a melon? This is because modern real-time 3D relies on low polygon models augmented with pixel level "tricks" to make up for it.

There are lots of cool thing we can do with the ability to process geometry on the GPU. We could see particle systems on the GPU, fine grained model details like fur that can be affected by the physical characteristics of the world, procedural geometry for highly dynamic environments, "real" displacement mapping, and geometry amplification that can add detail to models. Some of these things may show up sooner than others in games, as we will still be limited by the performance of the hardware when it comes to implementing these features.

There are, of course, other benefits to DX10. We explored this in previous articles for those who are interested, but here's a quick run down. Object and state change overhead has been decreased, allowing for less CPU involvement when sending data to the GPU. This should improve performance and give developers more headroom in building larger, more complex scenes. We have more rigidly defined specifications, which means developers can focus less on how individual hardware will handle their game and more on the features they want to implement. With a larger focus on data types and accuracy, the results of calculations will be more consistent between hardware, and developers will have more flexibility in choosing how their data is processed.

In general, DX10 also offers a more generic computing model with lots of flexibility. This will be very important going forward, but right now developers still have de facto limitations on shader length and complexity based on the performance of the hardware that currently exists. As developers better learn how to use the flexibility they have, and as hardware designers continue to deliver higher performance year after year, we will see DirectX 10 applications slowly start to blossom into what everyone has dreamed they could be.

For now, before we get into features and performance, we would like to temper your expectations. Many of the features currently implemented in DirectX 10 could also be done using DirectX 9. Additionally, those features that are truly DX10 only either don't add much beyond what we would get otherwise, or require quite a bit of processing power to handle. Thus, we either get something that was already possible or something that requires expensive hardware.