Shortly after the specification-unveil of the Xbox Series X, Microsoft announced the DirectX 12 Ultimate API for the next-gen gaming PCs and the accompanying XSX console. While it basically it’s an incremental upgrade over the existing DirectX 12 (tier 1.1), its core advantage is cross-platform support: Both the next-gen Xbox Series X as well as the latest PC games will leverage it. This not only simplifies cross-platform porting but also makes it easier for developers to optimize their games for the latest hardware.
By the time, the Xbox Series X arrives later this year, game developers will have already had enough time with hardware using the same graphics API (NVIDIA’s Turing), simplifying the porting and optimization process. At the same time, this will also improve utilization on the latest PC hardware, improving the overall performance. All in all, it’s another step by Microsoft to unify the Xbox and PC gaming platforms.
Other than that, it also incorporates pipeline optimizations earlier introduced by DX12 and NVIDIA’s Turing GPUs such as Mesh Shaders, Variable Rate Shading and Sampler Feedback. We’ve already explained the first two in out DX12 deep-dive, you can read that here:
As for Sampler Feedback, it basically allows the game engine to reduce the overall shading with respect to the LOD, sampling, and filtering by recycling existing data. There is certain shading that can be reused either across frames or spatially to reduce GPU load while maintaining the same graphics quality.
This is especially important in VR where every frame counts. You can reproject the frame displayed on one eye on the other, essentially doubling the performance without having any apparent impact on quality.
This can be done across frames as well (temporally). In a relatively static image, objects in the distance can reuse shading over multiple frames, for example, over each two to four frames and even more. The graphics performance saved can be used to increase the quality of nearby objects or places that have a more apparent impact on quality.