Ray tracing acceleration provisional extensions to standard announced

2 min read

The Khronos Group, an open consortium of industry-leading companies creating advanced interoperability standards, have announced the ratification and public release of extensions to the Vulkan Ray Tracing standard.

The announcement sees the creation of the industry’s first open, cross-vendor, cross-platform standard for ray tracing acceleration.

Focused on meeting desktop market demand for both real-time and offline rendering, the release of Vulkan Ray Tracing as provisional extensions enables the developer community to provide feedback before the specifications are finalised. Comments and feedback will be collected through the Vulkan GitHub Issues Tracker and Khronos Developer Slack.

Developers are also being encouraged to share comments with their preferred hardware vendors. The specifications are available on the Vulkan Registry.

Ray tracing is a rendering technique that is able to simulate how light rays intersect and interact with scene geometry, materials, and light sources to generate photorealistic imagery. It is widely used for film and other production rendering and is beginning to be practical for real-time applications and games. Vulkan Ray Tracing seamlessly integrates a coherent ray tracing framework into the Vulkan API, enabling a flexible merging of rasterization and ray tracing acceleration.

Vulkan Ray Tracing is designed to be hardware agnostic and so can be accelerated on both existing GPU compute and dedicated ray tracing cores if available.

“There has been strong developer demand for a truly cross-platform ray tracing acceleration API and now Vulkan Ray Tracing is here to meet that industry need,” said Daniel Koch, senior graphics system software engineer at NVIDIA and Vulkan Ray Tracing task sub group chair at Khronos. “The overall architecture of Vulkan Ray Tracing will be familiar to users of existing proprietary ray tracing APIs, which enables straightforward porting of existing ray traced content, but this framework also introduces new functionality and implementation flexibility.”

Vulkan Ray Tracing consists of a number of Vulkan, SPIR-V, and GLSL extensions, some of which are optional. The primaryVK_KHR_ray_tracing extension provides support for acceleration structure building and management, ray tracing shader stages and pipelines, and ray query intrinsics for all shader stages. VK_KHR_pipeline_library provides the ability to provide a set of shaders which can be efficiently linked into ray tracing pipelines.VK_KHR_deferred_host_operations enables intensive driver operations, including ray tracing pipeline compilation or CPU-based acceleration structure construction to be offloaded to application-managed CPU thread pools.

Vulkan Ray Tracing shaders are SPIR-V binaries which use two new extensions. TheSPV_KHR_ray_tracing SPIR-V extension adds support for ray tracing shader stages and instructions; SPV_KHR_ray_query adds support for ray query shader instructions. Developers can generate those binaries in GLSL using two new GLSL extensions, GLSL_EXT_ray_tracingand GLSL_EXT_ray_query, which are supported in the open source glslang compiler. Engineers at Khronos member companies, including NVIDIA, have also added support for the SPIR-Vextensions to DXC, Microsoft’s open source HLSL compiler, enabling Vulkan Ray Tracing SPIR-V shaders to be authored in HLSL using the syntax defined by Microsoft, with minimal modifications.

“Standardising ray tracing in Vulkan is an important step towards making ray tracing available across a wide range of devices, as well as enabling developers to use this technology to its full advantage," said Andrej Zdravkovic, senior vice president, software development, AMD.

“Epic Games has been an active member of the Vulkan Ray Tracing group from the beginning, and we are happy to see the ray tracing extension released to the public. We at Epic Games continue to wholeheartedly support Khronos’s efforts on creating open standards to enhance the end-user experience,” added Yuriy O’Donnell, rendering engineer, Epic Games.