Khronos Group ratifies Vulkan ray tracing platform
Claimed to be the first open, cross-vendor, cross platform standard for ray tracing acceleration, Vulkan is for desktop real-time and offline rendering.
Vulkan is an open, royalty-free application programming interface (API) for high-efficiency, cross-platform access to modern graphic processor units (GPUs). It is supported in a range of devices from Windows and Linux PCs, consoles, and the cloud, to mobile phones and embedded platforms.
Ray tracing is a rendering technique that realistically simulates 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 rasterisation and ray tracing acceleration. Vulkan 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,” 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 primary VK_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.
Shaders are SPIR-V binaries which use two new extensions. The SPV_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_tracing and GLSL_EXT_ray_query, which are supported in the open source glslang compiler. Engineers at Khronos member companies have also added support for the SPIR-V extensions 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, says Kronos.
A Vulkan software development kit (SDK) is also available.
“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. AMD intends to provide support for all of the major features in this extension, including ray shading, ray queries, and CPU acceleration structure management,” said Andrej Zdravkovic, senior vice president, software development, AMD.
“Allowing ray queries from any shader stage is a great feature, which will both simplify integrations and open up the possibility for new techniques while multithreaded host-side building of acceleration structures has the potential to reduce latency and improve the performance of our upcoming game titles,” said Sebastian Tafuri, senior rendering engineer at Frostbite, EA.
Morgan McGuire, research director at Nvidia, added: “Bringing accelerated ray tracing to the Vulkan cross-platform, open standard API is another significant step towards enabling the highest quality of visual realism for real-time games and applications everywhere.”
PIC: Real-time Ray Tracing Effects in Wolfenstein Youngblood.JPG
