Rasterization has been the dominant method to produce interactive graphics, but increasing performance of graphics hardware has made ray tracing a viable option for interactive rendering. Being able to integrate ray tracing with traditional rasterization makes it easier for applications to incrementally add ray traced effects to existing applications or to do hybrid approaches with rasterization for primary visibility and ray tracing for secondary queries.

To enable ray tracing, this extension adds a few different categories of new functionality:

• A new ray tracing pipeline type with new shader domains: ray generation, intersection, any-hit, closest hit, miss, and callable
• A shader binding indirection table to link shader groups with acceleration structure items
• Ray tracing commands which initiate the ray pipeline traversal and invocation of the various new shader domains depending on which traversal conditions are met

This extension adds support for the following SPIR-V extension in Vulkan:

• SPV_KHR_ray_tracing

Sample Code

Example ray generation GLSL shader

#version 450 core
#extension GL_EXT_ray_tracing : require
layout(set = 0, binding = 0, rgba8) uniform image2D image;
layout(set = 0, binding = 1) uniform accelerationStructureEXT as;
layout(location = 0) rayPayloadEXT float payload;

void main()
{
   vec4 col = vec4(0, 0, 0, 1);

   vec3 origin = vec3(float(gl_LaunchIDEXT.x)/float(gl_LaunchSizeEXT.x), float(gl_LaunchIDEXT.y)/float(gl_LaunchSizeEXT.y), 1.0);
   vec3 dir = vec3(0.0, 0.0, -1.0);

   traceRayEXT(as, 0, 0xff, 0, 1, 0, origin, 0.0, dir, 1000.0, 0);

   col.y = payload;

   imageStore(image, ivec2(gl_LaunchIDEXT.xy), col);
}

VK_KHR_ray_tracing_pipeline

Name String

VK_KHR_ray_tracing_pipeline

Extension Type

Device extension

Registered Extension Number

348

Revision

1

Extension and Version Dependencies

VK_KHR_spirv_1_4 and VK_KHR_acceleration_structure

Contact

• Daniel Koch dgkoch

Other Extension Metadata

Last Modified Date

2020-11-12

Interactions and External Dependencies

• This extension requires SPV_KHR_ray_tracing
• This extension provides API support for GLSL_EXT_ray_tracing
• This extension interacts with Vulkan 1.2 and VK_KHR_vulkan_memory_model, adding the shader-call-related relation of invocations, shader-call-order partial order of dynamic instances of instructions, and the ShaderCallKHR scope.
• This extension interacts with VK_KHR_pipeline_library, enabling pipeline libraries to be used with ray tracing pipelines and enabling usage of VkRayTracingPipelineInterfaceCreateInfoKHR.

Contributors

• Matthäus Chajdas, AMD
• Greg Grebe, AMD
• Nicolai Hähnle, AMD
• Tobias Hector, AMD
• Dave Oldcorn, AMD
• Skyler Saleh, AMD
• Mathieu Robart, Arm
• Marius Bjorge, Arm
• Tom Olson, Arm
• Sebastian Tafuri, EA
• Henrik Rydgard, Embark
• Juan Cañada, Epic Games
• Patrick Kelly, Epic Games
• Yuriy O’Donnell, Epic Games
• Michael Doggett, Facebook/Oculus
• Andrew Garrard, Imagination
• Don Scorgie, Imagination
• Dae Kim, Imagination
• Joshua Barczak, Intel
• Slawek Grajewski, Intel
• Jeff Bolz, NVIDIA
• Pascal Gautron, NVIDIA
• Daniel Koch, NVIDIA
• Christoph Kubisch, NVIDIA
• Ashwin Lele, NVIDIA
• Robert Stepinski, NVIDIA
• Martin Stich, NVIDIA
• Nuno Subtil, NVIDIA
• Eric Werness, NVIDIA
• Jon Leech, Khronos
• Jeroen van Schijndel, OTOY
• Juul Joosten, OTOY
• Alex Bourd, Qualcomm
• Roman Larionov, Qualcomm
• David McAllister, Qualcomm
• Spencer Fricke, Samsung
• Lewis Gordon, Samsung
• Ralph Potter, Samsung
• Jasper Bekkers, Traverse Research
• Jesse Barker, Unity
• Baldur Karlsson, Valve