Some News on DirectX 12
First up, let's talk about DirectX 12. As we near the release of Windows 10 this summer you'll hear more about DX12 than you could ever imagine, with Intel, AMD and NVIDIA all banging the drum loud and clear. At this point, not everything can be divulged but NVIDIA wanted to be sure we understood that there were two very different aspects of the DX12 story: better CPU utilizing and efficiency along with new features that require new hardware. We have all heard the stories (ours included) talking about the backwards compatibility of DX12 for currently shipping GPUs, but that only accounts for the improved CPU utilization and efficiency portions of DX12. While that is critically important, there are indeed new features that require new GPU hardware to take advantage of, just like in all previous DirectX releases.
In terms of new features, there are currently two different feature levels: Feature Level 12.0 and Feature Level 12.1. Feature level 12.0 supports new rendering technologies like tiled resources, bindless textures and typed UAV access. 12.1 is more advanced and includes the 12.0 features but adds conservative raster and raster ordered views.
NVIDIA says that GM200 supports another feature as well: volume tiled resources. This additional feature brings support for 3D textures to be used in the tiled resource capability, utilizing less memory by only storing the specific tiles of textures required for rendering at that time. The tiled resources feature listed as a requirement for Feature Level 12.0 only needs to support 2D textures. With a 3D texture though a developer has the ability to store an additional dimension of data; NVIDIA gave an example of smoke where the third dimension of texture might indicate the pressure of the fluid, changing the color and response of the physics based on that 3rd dimension of data.
Conservative raster improves pixel coverage determination moving away from specific sample points and instead will register as covered if any portion of the pixel is covered by the geometry in question. This does come with some kind of performance penalty, of course, but it has the ability to improve coverage recognition for better image quality with new rendering techniques. NVIDIA gave the example of ray traced shadows that are free of aliasing image quality issues.
There is a still lot yet to be shown or discussed about DX12 but we can confirm now that Maxwell will support DirectX 12 Feature Level 12.1 as well as the volume tiled resources capability. I'm sure we'll hear AMD's side of this story very soon as well and hopefully some news from Microsoft this summer will help us better understand the overall direction of the API.
