Khronos Group, the folks who look after OpenGL and the Vulkan graphics API, recently announced official ray-tracing extensions for Vulkan. This comes as great news for people looking forward to the widespread adoption of ray-tracing tech in modern games. Unlike HairWorks, PhysX, and Turfworks (ew), ray-tracing appears to be here to stay, and with Khronos’ open-source blessing, it’ll almost certainly make its way out of Nvidia’s RTX walled garden.
The announcement came shortly after Microsoft unveiled detailed specs for the Xbox Series X, including hardware support for ray-tracing. The official Khronos-sanctioned Vulkan ray-tracing extensions aren’t exactly the first. Nvidia’s proprietary ray-tracing extensions to implement RTX features under Vulkan in Wolfenstein: New Blood.
The official branch appears to change little, apart from replacing references to Nvidia (prefixed as NV), with VK. This also means that porting existing code over will involve a “trivial” amount of effort.
As mentioned earlier, the aim of Vulkan ray-tracing support isn’t to offer something radically new. Going by Khronos’ own feature comparison, it appears that the Vulkan codepath will offer feature parity with Microsoft’s DXR 1.1. Effectively, this means that developers can pick and choose to run ray-tracing effects on either DirectX 12 or Vulkan. Vulkan’s famed performance improvements mean that we might see ray-traced titles that don’t completely choke on PC.
Everything isn’t much of a muchness, though. A key addition that the announcement talks about is an optional feature called “Build Acceleration Structures on Host.” What this does is that it allows developers to utilise idle CPU resources to build hierarchical data structures optimized for ray tracing, called acceleration structures. By offloading some of the work to the CPU, we might see some performance improvements, especially on systems with 12 or more threads.
On the surface, Vulkan support for support might not seem that important: we already have DXR in place and Nvidia-supported supported extensions for games that Vulkan. However, it’s important to note here that DXR is proprietary Microsoft tech. Google Stadia exclusives runs games on Vulkan and the PS5, similarly, won’t be leveraging DirectX. Vulkan ray-tracing supports offers both of these platforms a viable open-source solution.
