Khronos releases final specification of Vulkan Raytracing standard
The Khronos Group has released the final Vulkan Raytracing specification. This open standard can be used free of charge by developers to add ray tracing to Vulkan games. A software development kit will follow in mid-December.
The final release is now on GitHub. Khronos now reports that Vulkan Raytracing “will be familiar to anyone who has used DirectX Raytracing.” At the same time, Khronos is introducing some new features. For example, the CPU of a system can be used to perform ray tracing setup operations, the consortium reports.
Khronos released early versions of the Vulkan ray tracing extensions back in March, but did not announce when the final specification would be released at the time. At that time, the consortium already shared various details about the extensions. Vulkan Raytracing is an open standard that is cross-vendor and ‘hardware agnostic’. This means that the standard in theory works on video cards from all manufacturers.
The standard can also function on GPUs without separate ray tracing hardware, although manufacturer support must be added via GPU drivers. AMD, Intel and Nvidia have already committed to supporting Vulkan Raytracing to some extent. In time, Vulkan Raytracing should even be supported on mobile platforms, Khronos reports.
Vulkan Raytracing’s release timeline. Image via the Khronos Group
Khronos has made several changes to the specification since March, which the consortium elaborates on in its announcement blog. For example, where the early version of Vulkan Raytracing extension consisted of a single extension, the final release split it into three different extensions. Respectively, these are separate extensions for ray tracing queries, pipelines, and acceleration. The consortium did this after feedback, which showed that ‘certain markets’ would like to support ray tracing queries without pipelines.
Therefore, with the final release, developers can choose to support these queries or pipelines extensions jointly or individually. Note that the acceleration extension is not optional: “The query and pipeline extensions depend on the VK_KHR_acceleration_structure extension to provide a common foundation for managing the acceleration structure.”
Furthermore, the dependencies for all extensions have been adjusted; Vulkan 1.1 and SPIR-V 1.4 are now requirements, Khronos reports. The acceleration structure and deferred host operations will also be adjusted, and less radical changes will be made to the ray tracing pipelines and ray queries themselves.
In addition to the final specification, Khronos also publishes a blog post discussing the implementation of ‘hybrid rendering’, where ray tracing is used to a limited extent, in combination with the more traditional rasterization. In this blog, Wolfenstein: Youngblood is mentioned as an example. That game currently uses a closed ray tracing standard from Nvidia, on which Vulkan Raytracing is based. It is not clear whether Youngblood will eventually receive support for the new, open standard.
Wolfenstein: Youngblood without ray tracing (left) and with ray tracing. Image via the Khronos Group