VulkanHub

VK_KHR_acceleration_structure

Other Extension Metadata

Last Modified Date

2021-09-30

Contributors
  • Samuel Bourasseau, Adobe
  • 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
  • Ricardo Garcia, Igalia
  • 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
  • Lewis Gordon, Samsung
  • Ralph Potter, Samsung
  • Jasper Bekkers, Traverse Research
  • Jesse Barker, Unity
  • Baldur Karlsson, Valve

Description

In order to be efficient, rendering techniques such as ray tracing need a quick way to identify which primitives may be intersected by a ray traversing the geometries. Acceleration structures are the most common way to represent the geometry spatially sorted, in order to quickly identify such potential intersections.

This extension adds new functionalities:

  • Acceleration structure objects and build commands
  • Structures to describe geometry inputs to acceleration structure builds
  • Acceleration structure copy commands

New Object Types

New Commands

New Structures

New Unions

New Enums

New Bitmasks

New Enum Constants

  • VK_KHR_ACCELERATION_STRUCTURE_EXTENSION_NAME
  • VK_KHR_ACCELERATION_STRUCTURE_SPEC_VERSION
  • Extending VkAccessFlagBits:
    • VK_ACCESS_ACCELERATION_STRUCTURE_READ_BIT_KHR
    • VK_ACCESS_ACCELERATION_STRUCTURE_WRITE_BIT_KHR
  • Extending VkBufferUsageFlagBits:
    • VK_BUFFER_USAGE_ACCELERATION_STRUCTURE_BUILD_INPUT_READ_ONLY_BIT_KHR
    • VK_BUFFER_USAGE_ACCELERATION_STRUCTURE_STORAGE_BIT_KHR
  • Extending VkDescriptorType:
    • VK_DESCRIPTOR_TYPE_ACCELERATION_STRUCTURE_KHR
  • Extending VkFormatFeatureFlagBits:
    • VK_FORMAT_FEATURE_ACCELERATION_STRUCTURE_VERTEX_BUFFER_BIT_KHR
  • Extending VkIndexType:
    • VK_INDEX_TYPE_NONE_KHR
  • Extending VkObjectType:
    • VK_OBJECT_TYPE_ACCELERATION_STRUCTURE_KHR
  • Extending VkPipelineStageFlagBits:
    • VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR
  • Extending VkQueryType:
    • VK_QUERY_TYPE_ACCELERATION_STRUCTURE_COMPACTED_SIZE_KHR
    • VK_QUERY_TYPE_ACCELERATION_STRUCTURE_SERIALIZATION_SIZE_KHR
  • Extending VkStructureType:
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_BUILD_GEOMETRY_INFO_KHR
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_BUILD_SIZES_INFO_KHR
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_CREATE_INFO_KHR
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_DEVICE_ADDRESS_INFO_KHR
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_AABBS_DATA_KHR
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_INSTANCES_DATA_KHR
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_KHR
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_TRIANGLES_DATA_KHR
    • VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_VERSION_INFO_KHR
    • VK_STRUCTURE_TYPE_COPY_ACCELERATION_STRUCTURE_INFO_KHR
    • VK_STRUCTURE_TYPE_COPY_ACCELERATION_STRUCTURE_TO_MEMORY_INFO_KHR
    • VK_STRUCTURE_TYPE_COPY_MEMORY_TO_ACCELERATION_STRUCTURE_INFO_KHR
    • VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_ACCELERATION_STRUCTURE_FEATURES_KHR
    • VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_ACCELERATION_STRUCTURE_PROPERTIES_KHR
    • VK_STRUCTURE_TYPE_WRITE_DESCRIPTOR_SET_ACCELERATION_STRUCTURE_KHR

If VK_EXT_debug_report is supported:

If VK_KHR_format_feature_flags2 or Vulkan Version 1.3 is supported:

Issues

(1) How does this extension differ from VK_NV_ray_tracing?

DISCUSSION:

The following is a summary of the main functional differences between VK_KHR_acceleration_structure and VK_NV_ray_tracing:

(2) Can you give a more detailed comparison of differences and similarities between VK_NV_ray_tracing and VK_KHR_acceleration_structure?

DISCUSSION:

The following is a more detailed comparison of which commands, structures, and enums are aliased, changed, or removed.

(3) What are the changes between the public provisional (VK_KHR_ray_tracing v8) release and the internal provisional (VK_KHR_ray_tracing v9) release?

(4) What are the changes between the internal provisional (VK_KHR_ray_tracing v9) release and the final (VK_KHR_acceleration_structure v11) release?

  • refactor VK_KHR_ray_tracing into 3 extensions, enabling implementation flexibility and decoupling ray query support from ray pipelines:
  • clarify buffer usage flags for ray tracing
    • VK_BUFFER_USAGE_RAY_TRACING_BIT_NV is left alone in VK_NV_ray_tracing (required on scratch and instanceData)
    • VK_BUFFER_USAGE_SHADER_BINDING_TABLE_BIT_KHR is added as an alias of VK_BUFFER_USAGE_RAY_TRACING_BIT_NV in VK_KHR_ray_tracing_pipeline and is required on shader binding table buffers
    • VK_BUFFER_USAGE_ACCELERATION_STRUCTURE_BUILD_INPUT_READ_ONLY_BIT_KHR is added in VK_KHR_acceleration_structure for all vertex, index, transform, aabb, and instance buffer data referenced by device build commands
    • VK_BUFFER_USAGE_STORAGE_BUFFER_BIT is used for scratchData
  • add max primitive counts (ppMaxPrimitiveCounts) to vkCmdBuildAccelerationStructuresIndirectKHR
  • Allocate acceleration structures from VkBuffers and add a mode to constrain the device address
    • de-alias VkBindAccelerationStructureMemoryInfoNV and vkBindAccelerationStructureMemoryNV, and remove VkBindAccelerationStructureMemoryInfoKHR, VkAccelerationStructureMemoryRequirementsInfoKHR, and vkGetAccelerationStructureMemoryRequirementsKHR
    • acceleration structures now take a VkBuffer and offset at creation time for memory placement
    • add a new VK_BUFFER_USAGE_ACCELERATION_STRUCTURE_STORAGE_BIT_KHR buffer usage for such buffers
    • add a new VK_ACCELERATION_STRUCTURE_TYPE_GENERIC_KHR acceleration structure type for layering
  • move VK_GEOMETRY_TYPE_INSTANCES_KHR to main enum instead of being added via extension
  • make build commands more consistent - all now build multiple acceleration structures and are named plurally (vkCmdBuildAccelerationStructuresIndirectKHR, vkCmdBuildAccelerationStructuresKHR, vkBuildAccelerationStructuresKHR)
  • add interactions with VK_DESCRIPTOR_SET_LAYOUT_CREATE_UPDATE_AFTER_BIND_POOL_BIT for acceleration structures, including a new feature (descriptorBindingAccelerationStructureUpdateAfterBind) and 3 new properties (maxPerStageDescriptorAccelerationStructures, maxPerStageDescriptorUpdateAfterBindAccelerationStructures, maxDescriptorSetUpdateAfterBindAccelerationStructures)
  • extension is no longer provisional
  • define synchronization requirements for builds, traces, and copies
  • define synchronization requirements for AS build inputs and indirect build buffer

(5) What is VK_ACCELERATION_STRUCTURE_TYPE_GENERIC_KHR for?

RESOLVED: It is primarily intended for API layering. In DXR, the acceleration structure is basically just a buffer in a special layout, and you do not know at creation time whether it will be used as a top or bottom level acceleration structure. We thus added a generic acceleration structure type whose type is unknown at creation time, but is specified at build time instead. Applications which are written directly for Vulkan should not use it.

Version History

  • Revision 1, 2019-12-05 (Members of the Vulkan Ray Tracing TSG)
    • Internal revisions (forked from VK_NV_ray_tracing)
  • Revision 2, 2019-12-20 (Daniel Koch, Eric Werness)
    • Add const version of DeviceOrHostAddress (!3515)
    • Add VU to clarify that only handles in the current pipeline are valid (!3518)
    • Restore some missing VUs and add in-place update language (#1902, !3522)
    • rename VkAccelerationStructureInstanceKHR member from accelerationStructure to accelerationStructureReference to better match its type (!3523)
    • Allow VK_ERROR_INVALID_OPAQUE_CAPTURE_ADDRESS for pipeline creation if shader group handles cannot be reused (!3523)
    • update documentation for the VK_ERROR_INVALID_OPAQUE_CAPTURE_ADDRESS error code and add missing documentation for new return codes from VK_KHR_deferred_host_operations (!3523)
    • list new query types for VK_KHR_ray_tracing (!3523)
    • Fix VU statements for VkAccelerationStructureGeometryKHR referring to correct union members and update to use more current wording (!3523)
  • Revision 3, 2020-01-10 (Daniel Koch, Jon Leech, Christoph Kubisch)
    • Fix 'instance of' and 'that/which contains/defines' markup issues (!3528)
    • factor out VK_KHR_pipeline_library as stand-alone extension (!3540)
    • Resolve Vulkan-hpp issues (!3543)
      • add missing require for VkGeometryInstanceFlagsKHR
      • de-alias VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_CREATE_INFO_NV since the KHR structure is no longer equivalent
      • add len to pDataSize attribute for vkWriteAccelerationStructuresPropertiesKHR
  • Revision 4, 2020-01-23 (Daniel Koch, Eric Werness)
    • Improve vkWriteAccelerationStructuresPropertiesKHR, add return value and VUs (#1947)
    • Clarify language to allow multiple raygen shaders (#1959)
    • Various editorial feedback (!3556)
    • Add language to help deal with looped self-intersecting fans (#1901)
    • Change vkCmdTraceRays{,Indirect}KHR args to pointers (!3559)
    • Add scratch address validation language (#1941, !3551)
    • Fix definition and add hierarchy information for shader call scope (#1977, !3571)
  • Revision 5, 2020-02-04 (Eric Werness, Jeff Bolz, Daniel Koch)
    • remove vestigial accelerationStructureUUID (!3582)
    • update definition of repack instructions and improve memory model interactions (#1910, #1913, !3584)
    • Fix wrong sType for VkPhysicalDeviceRayTracingFeaturesKHR (#1988)
    • Use provisional SPIR-V capabilities (#1987)
    • require rayTraversalPrimitiveCulling if rayQuery is supported (#1927)
    • Miss shaders do not have object parameters (!3592)
    • Fix missing required types in XML (!3592)
    • clarify matching conditions for update (!3592)
    • add goal that host and device builds be similar (!3592)
    • clarify that maxPrimitiveCount limit should apply to triangles and AABBs (!3592)
    • Require alignment for instance arrayOfPointers (!3592)
    • Zero is a valid value for instance flags (!3592)
    • Add some alignment VUs that got lost in refactoring (!3592)
    • Recommend TMin epsilon rather than culling (!3592)
    • Get angle from dot product not cross product (!3592)
    • Clarify that AH can access the payload and attributes (!3592)
    • Match DXR behavior for inactive primitive definition (!3592)
    • Use a more generic term than degenerate for inactive to avoid confusion (!3592)
  • Revision 6, 2020-02-20 (Daniel Koch)
    • fix some dangling NV references (#1996)
    • rename VkCmdTraceRaysIndirectCommandKHR to VkTraceRaysIndirectCommandKHR (!3607)
    • update contributor list (!3611)
    • use uint64_t instead of VkAccelerationStructureReferenceKHR in VkAccelerationStructureInstanceKHR (#2004)
  • Revision 7, 2020-02-28 (Tobias Hector)
    • remove HitTKHR SPIR-V builtin (spirv/spirv-extensions#7)
  • Revision 8, 2020-03-06 (Tobias Hector, Dae Kim, Daniel Koch, Jeff Bolz, Eric Werness)
    • explicitly state that Tmax is updated when new closest intersection is accepted (#2020,!3536)
    • Made references to min and max t values consistent (!3644)
    • finish enumerating differences relative to VK_NV_ray_tracing in issues (1) and (2) (#1974,!3642)
    • fix formatting in some math equations (!3642)
    • Restrict the Hit Kind operand of OpReportIntersectionKHR to 7-bits (spirv/spirv-extensions#8,!3646)
    • Say ray tracing ':normative{type="should"}' be watertight (#2008,!3631)
    • Clarify memory requirements for ray tracing buffers (#2005,!3649)
    • Add callable size limits (#1997,!3652)
  • Revision 9, 2020-04-15 (Eric Werness, Daniel Koch, Tobias Hector, Joshua Barczak)
    • Add geometry flags to acceleration structure creation (!3672)
    • add build scratch memory alignment (minAccelerationStructureScratchOffsetAlignment) (#2065,!3725)
    • fix naming and return enum from vkGetDeviceAccelerationStructureCompatibilityKHR (#2051,!3726)
    • require SPIR-V 1.4 (#2096,!3777)
    • added creation time capture/replay flags (#2104,!3774)
    • require Vulkan 1.1 (#2133,!3806)
    • use device addresses instead of VkBuffers for ray tracing commands (#2074,!3815)
    • add interactions with Vulkan 1.2 and VK_KHR_vulkan_memory_model (#2133,!3830)
    • make VK_KHR_pipeline_library an interaction instead of required (#2045,#2108,!3830)
    • make VK_KHR_deferred_host_operations an interaction instead of required (#2045,!3830)
    • removed maxCallableSize and added explicit stack size management for ray pipelines (#1997,!3817,!3772,!3844)
    • improved documentation for VkAccelerationStructureVersionInfoKHR (#2135,3835)
    • rename VkAccelerationStructureBuildOffsetInfoKHR to VkAccelerationStructureBuildRangeInfoKHR (#2058,!3754)
    • Re-unify geometry description between build and create (!3754)
    • Fix ppGeometries ambiguity, add pGeometries (#2032,!3811)
    • add interactions with VK_EXT_robustness2 and allow nullDescriptor support for acceleration structures (#1920,!3848)
    • added future extensibility for AS updates (#2114,!3849)
    • Fix VU for dispatchrays and add a limit on the size of the full grid (#2160,!3851)
    • Add shaderGroupHandleAlignment property (#2180,!3875)
    • Clarify deferred host ops for pipeline creation (#2067,!3813)
    • Change acceleration structure build to always be sized (#2131,#2197,#2198,!3854,!3883,!3880)
  • Revision 10, 2020-07-03 (Mathieu Robart, Daniel Koch, Eric Werness, Tobias Hector)
    • Decomposition of the specification, from VK_KHR_ray_tracing to VK_KHR_acceleration_structure (#1918,!3912)
    • clarify buffer usage flags for ray tracing (#2181,!3939)
    • add max primitive counts to build indirect command (#2233,!3944)
    • Allocate acceleration structures from VkBuffers and add a mode to constrain the device address (#2131,!3936)
    • Move VK_GEOMETRY_TYPE_INSTANCES_KHR to main enum (#2243,!3952)
    • make build commands more consistent (#2247,!3958)
    • add interactions with UPDATE_AFTER_BIND (#2128,!3986)
    • correct and expand build command VUs (!4020)
    • fix copy command VUs (!4018)
    • added various alignment requirements (#2229,!3943)
    • fix valid usage for arrays of geometryCount items (#2198,!4010)
    • define what is allowed to change on RTAS updates and relevant VUs (#2177,!3961)
  • Revision 11, 2020-11-12 (Eric Werness, Josh Barczak, Daniel Koch, Tobias Hector)
    • de-alias NV and KHR acceleration structure types and associated commands (#2271,!4035)
    • specify alignment for host copy commands (#2273,!4037)
    • document VK_FORMAT_FEATURE_ACCELERATION_STRUCTURE_VERTEX_BUFFER_BIT_KHR
    • specify that acceleration structures are non-linear (#2289,!4068)
    • add several missing VUs for strides, vertexFormat, and indexType (#2315,!4069)
    • restore VUs for VkAccelerationStructureBuildGeometryInfoKHR (#2337,!4098)
    • ban multi-instance memory for host operations (#2324,!4102)
    • allow dstAccelerationStructure to be null for vkGetAccelerationStructureBuildSizesKHR (#2330,!4111)
    • more build VU cleanup (#2138,#4130)
    • specify host endianness for AS serialization (#2261,!4136)
    • add invertible transform matrix VU (#1710,!4140)
    • require geometryCount to be 1 for TLAS builds (!4145)
    • improved validity conditions for build addresses (#4142)
    • add single statement SPIR-V VUs, build limit VUs (!4158)
    • document limits for vertex and aabb strides (#2390,!4184)
    • specify that VK_PIPELINE_STAGE_ACCELERATION_STRUCTURE_BUILD_BIT_KHR applies to AS copies (#2382,#4173)
    • define sync for AS build inputs and indirect buffer (#2407,!4208)
  • Revision 12, 2021-08-06 (Samuel Bourasseau)
    • rename VK_GEOMETRY_INSTANCE_TRIANGLE_FRONT_COUNTERCLOCKWISE_BIT_KHR to VK_GEOMETRY_INSTANCE_TRIANGLE_FLIP_FACING_BIT_KHR (keep previous as alias).
    • Clarify description and add note.
  • Revision 13, 2021-09-30 (Jon Leech)