VK_KHR_acceleration_structure(3)

# VK_KHR_acceleration_structure(3) Manual Page

## Name

VK_KHR_acceleration_structure - device extension

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## Registered Extension Number

151

## Revision

11

## Extension and Version Dependencies

- Requires Vulkan 1.1

- Requires `VK_EXT_descriptor_indexing`

- Requires `VK_KHR_buffer_device_address`

- Requires `VK_KHR_deferred_host_operations`

### Other Extension Metadata

Last Modified Date

  2020-11-12

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

  - 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

- VkAccelerationStructureKHR

### New Commands

- vkBuildAccelerationStructuresKHR

- vkCmdBuildAccelerationStructuresIndirectKHR

- vkCmdBuildAccelerationStructuresKHR

- vkCmdCopyAccelerationStructureKHR

- vkCmdCopyAccelerationStructureToMemoryKHR

- vkCmdCopyMemoryToAccelerationStructureKHR

- vkCmdWriteAccelerationStructuresPropertiesKHR

- vkCopyAccelerationStructureKHR

- vkCopyAccelerationStructureToMemoryKHR

- vkCopyMemoryToAccelerationStructureKHR

- vkCreateAccelerationStructureKHR

- vkDestroyAccelerationStructureKHR

- vkGetAccelerationStructureBuildSizesKHR

- vkGetAccelerationStructureDeviceAddressKHR

- vkGetDeviceAccelerationStructureCompatibilityKHR

- vkWriteAccelerationStructuresPropertiesKHR

### New Structures

- VkAabbPositionsKHR

- VkAccelerationStructureBuildGeometryInfoKHR

- VkAccelerationStructureBuildRangeInfoKHR

- VkAccelerationStructureBuildSizesInfoKHR

- VkAccelerationStructureCreateInfoKHR

- VkAccelerationStructureDeviceAddressInfoKHR

- VkAccelerationStructureGeometryAabbsDataKHR

- VkAccelerationStructureGeometryInstancesDataKHR

- VkAccelerationStructureGeometryKHR

- VkAccelerationStructureGeometryTrianglesDataKHR

- VkAccelerationStructureInstanceKHR

- VkAccelerationStructureVersionInfoKHR

- VkCopyAccelerationStructureInfoKHR

- VkCopyAccelerationStructureToMemoryInfoKHR

- VkCopyMemoryToAccelerationStructureInfoKHR

- VkTransformMatrixKHR

- Extending VkPhysicalDeviceFeatures2, VkDeviceCreateInfo:

  - VkPhysicalDeviceAccelerationStructureFeaturesKHR

- Extending VkPhysicalDeviceProperties2:

  - VkPhysicalDeviceAccelerationStructurePropertiesKHR

- Extending VkWriteDescriptorSet:

  - VkWriteDescriptorSetAccelerationStructureKHR

### New Unions

- VkAccelerationStructureGeometryDataKHR

- VkDeviceOrHostAddressConstKHR

- VkDeviceOrHostAddressKHR

### New Enums

- VkAccelerationStructureBuildTypeKHR

- VkAccelerationStructureCompatibilityKHR

- VkAccelerationStructureCreateFlagBitsKHR

- VkAccelerationStructureTypeKHR

- VkBuildAccelerationStructureFlagBitsKHR

- VkBuildAccelerationStructureModeKHR

- VkCopyAccelerationStructureModeKHR

- VkGeometryFlagBitsKHR

- VkGeometryInstanceFlagBitsKHR

- VkGeometryTypeKHR

### New Bitmasks

- VkAccelerationStructureCreateFlagsKHR

- VkBuildAccelerationStructureFlagsKHR

- VkGeometryFlagsKHR

- VkGeometryInstanceFlagsKHR

### 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 VkDebugReportObjectTypeEXT:

  - `VK_DEBUG_REPORT_OBJECT_TYPE_ACCELERATION_STRUCTURE_KHR_EXT`

- 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`

### 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:

- added acceleration structure serialization / deserialization (`VK_COPY_ACCELERATION_STRUCTURE_MODE_SERIALIZE_KHR`, `VK_COPY_ACCELERATION_STRUCTURE_MODE_DESERIALIZE_KHR`, vkCmdCopyAccelerationStructureToMemoryKHR, vkCmdCopyMemoryToAccelerationStructureKHR)

- document inactive primitives and instances

- added VkPhysicalDeviceAccelerationStructureFeaturesKHR structure

- added indirect and batched acceleration structure builds (vkCmdBuildAccelerationStructuresIndirectKHR)

- added host acceleration structure commands

- reworked geometry structures so they could be better shared between device, host, and indirect builds

- explicitly made VkAccelerationStructureKHR use device addresses

- added acceleration structure compatibility check function (vkGetDeviceAccelerationStructureCompatibilityKHR)

- add parameter for requesting memory requirements for host and/or device build

- added format feature for acceleration structure build vertex formats (`VK_FORMAT_FEATURE_ACCELERATION_STRUCTURE_VERTEX_BUFFER_BIT_KHR`)

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

DISCUSSION:

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

- Aliased functionality — enums, structures, and commands that are considered equivalent:

  - VkGeometryTypeNV ↔ VkGeometryTypeKHR

  - VkAccelerationStructureTypeNV ↔ VkAccelerationStructureTypeKHR

  - VkCopyAccelerationStructureModeNV ↔ VkCopyAccelerationStructureModeKHR

  - VkGeometryFlagsNV ↔ VkGeometryFlagsKHR

  - VkGeometryFlagBitsNV ↔ VkGeometryFlagBitsKHR

  - VkGeometryInstanceFlagsNV ↔ VkGeometryInstanceFlagsKHR

  - VkGeometryInstanceFlagBitsNV ↔ VkGeometryInstanceFlagBitsKHR

  - VkBuildAccelerationStructureFlagsNV ↔ VkBuildAccelerationStructureFlagsKHR

  - VkBuildAccelerationStructureFlagBitsNV ↔ VkBuildAccelerationStructureFlagBitsKHR

  - VkTransformMatrixNV ↔ VkTransformMatrixKHR (added to VK_NV_ray_tracing for descriptive purposes)

  - VkAabbPositionsNV ↔ VkAabbPositionsKHR (added to VK_NV_ray_tracing for descriptive purposes)

  - VkAccelerationStructureInstanceNV ↔ VkAccelerationStructureInstanceKHR (added to VK_NV_ray_tracing for descriptive purposes)

- Changed enums, structures, and commands:

  - renamed `VK_GEOMETRY_INSTANCE_TRIANGLE_CULL_DISABLE_BIT_NV` → `VK_GEOMETRY_INSTANCE_TRIANGLE_FACING_CULL_DISABLE_BIT_KHR` in VkGeometryInstanceFlagBitsKHR

  - VkGeometryTrianglesNV → VkAccelerationStructureGeometryTrianglesDataKHR (device or host address instead of buffer+offset)

  - VkGeometryAABBNV → VkAccelerationStructureGeometryAabbsDataKHR (device or host address instead of buffer+offset)

  - VkGeometryDataNV → VkAccelerationStructureGeometryDataKHR (union of triangle/aabbs/instances)

  - VkGeometryNV → VkAccelerationStructureGeometryKHR (changed type of geometry)

  - VkAccelerationStructureCreateInfoNV → VkAccelerationStructureCreateInfoKHR (reshuffle geometry layout/info)

  - VkPhysicalDeviceRayTracingPropertiesNV → VkPhysicalDeviceAccelerationStructurePropertiesKHR (for acceleration structure properties, renamed `maxTriangleCount` to `maxPrimitiveCount`, added per stage and update after bind limits) and VkPhysicalDeviceRayTracingPipelinePropertiesKHR (for ray tracing pipeline properties)

  - VkAccelerationStructureMemoryRequirementsInfoNV (deleted - replaced by allocating on top of VkBuffer)

  - VkWriteDescriptorSetAccelerationStructureNV → VkWriteDescriptorSetAccelerationStructureKHR (different acceleration structure type)

  - vkCreateAccelerationStructureNV → vkCreateAccelerationStructureKHR (device address, different geometry layout/info)

  - vkGetAccelerationStructureMemoryRequirementsNV (deleted - replaced by allocating on top of VkBuffer)

  - vkCmdBuildAccelerationStructureNV → vkCmdBuildAccelerationStructuresKHR (params moved to structs, layout differences)

  - vkCmdCopyAccelerationStructureNV → vkCmdCopyAccelerationStructureKHR (params to struct, extendable)

  - vkGetAccelerationStructureHandleNV → vkGetAccelerationStructureDeviceAddressKHR (device address instead of handle)

  - VkAccelerationStructureMemoryRequirementsTypeNV → size queries for scratch space moved to vkGetAccelerationStructureBuildSizesKHR

  - vkDestroyAccelerationStructureNV → vkDestroyAccelerationStructureKHR (different acceleration structure types)

  - vkCmdWriteAccelerationStructuresPropertiesNV → vkCmdWriteAccelerationStructuresPropertiesKHR (different acceleration structure types)

- Added enums, structures and commands:

  - `VK_GEOMETRY_TYPE_INSTANCES_KHR` to VkGeometryTypeKHR enum

  - `VK_COPY_ACCELERATION_STRUCTURE_MODE_SERIALIZE_KHR`, `VK_COPY_ACCELERATION_STRUCTURE_MODE_DESERIALIZE_KHR` to VkCopyAccelerationStructureModeKHR enum

  - VkPhysicalDeviceAccelerationStructureFeaturesKHR structure

  - VkAccelerationStructureBuildTypeKHR enum

  - VkBuildAccelerationStructureModeKHR enum

  - VkDeviceOrHostAddressKHR and VkDeviceOrHostAddressConstKHR unions

  - VkAccelerationStructureBuildRangeInfoKHR struct

  - VkAccelerationStructureGeometryInstancesDataKHR struct

  - VkAccelerationStructureDeviceAddressInfoKHR struct

  - VkAccelerationStructureVersionInfoKHR struct

  - VkStridedDeviceAddressRegionKHR struct

  - VkCopyAccelerationStructureToMemoryInfoKHR struct

  - VkCopyMemoryToAccelerationStructureInfoKHR struct

  - VkCopyAccelerationStructureInfoKHR struct

  - vkBuildAccelerationStructuresKHR command (host build)

  - vkCopyAccelerationStructureKHR command (host copy)

  - vkCopyAccelerationStructureToMemoryKHR (host serialize)

  - vkCopyMemoryToAccelerationStructureKHR (host deserialize)

  - vkWriteAccelerationStructuresPropertiesKHR (host properties)

  - vkCmdCopyAccelerationStructureToMemoryKHR (device serialize)

  - vkCmdCopyMemoryToAccelerationStructureKHR (device deserialize)

  - vkGetDeviceAccelerationStructureCompatibilityKHR (serialization)

(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?

- added `geometryFlags` to `VkAccelerationStructureCreateGeometryTypeInfoKHR` (later reworked to obsolete this)

- added `minAccelerationStructureScratchOffsetAlignment` property to VkPhysicalDeviceRayTracingPropertiesKHR

- fix naming and return enum from vkGetDeviceAccelerationStructureCompatibilityKHR

  - renamed `VkAccelerationStructureVersionKHR` to VkAccelerationStructureVersionInfoKHR

  - renamed `VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_VERSION_KHR` to `VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_VERSION_INFO_KHR`

  - removed `VK_ERROR_INCOMPATIBLE_VERSION_KHR`

  - added VkAccelerationStructureCompatibilityKHR enum

  - remove return value from vkGetDeviceAccelerationStructureCompatibilityKHR and added return enum parameter

- Require Vulkan 1.1

- added creation time capture and replay flags

  - added VkAccelerationStructureCreateFlagBitsKHR and VkAccelerationStructureCreateFlagsKHR

  - renamed the `flags` member of VkAccelerationStructureCreateInfoKHR to `buildFlags` (later removed) and added the `createFlags` member

- change vkCmdBuildAccelerationStructuresIndirectKHR to use buffer device address for indirect parameter

- make VK_KHR_deferred_host_operations an interaction instead of a required extension (later went back on this)

- renamed `VkAccelerationStructureBuildOffsetInfoKHR` to VkAccelerationStructureBuildRangeInfoKHR

  - renamed the `ppOffsetInfos` parameter of vkCmdBuildAccelerationStructuresKHR to `ppBuildRangeInfos`

- Re-unify geometry description between build and create

  - remove `VkAccelerationStructureCreateGeometryTypeInfoKHR` and `VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_CREATE_GEOMETRY_TYPE_INFO_KHR`

  - added `VkAccelerationStructureCreateSizeInfoKHR` structure (later removed)

  - change type of the `pGeometryInfos` member of VkAccelerationStructureCreateInfoKHR from `VkAccelerationStructureCreateGeometryTypeInfoKHR` to VkAccelerationStructureGeometryKHR (later removed)

  - added `pCreateSizeInfos` member to VkAccelerationStructureCreateInfoKHR (later removed)

- Fix ppGeometries ambiguity, add pGeometries

  - remove `geometryArrayOfPointers` member of VkAccelerationStructureBuildGeometryInfoKHR

  - disambiguate two meanings of `ppGeometries` by explicitly adding `pGeometries` to the VkAccelerationStructureBuildGeometryInfoKHR structure and require one of them be `NULL`

- added nullDescriptor support for acceleration structures

- changed the `update` member of VkAccelerationStructureBuildGeometryInfoKHR from a bool to the `mode` VkBuildAccelerationStructureModeKHR enum which allows future extensibility in update types

- Clarify deferred host ops for pipeline creation

  - VkDeferredOperationKHR is now a top-level parameter for vkBuildAccelerationStructuresKHR, vkCreateRayTracingPipelinesKHR, vkCopyAccelerationStructureToMemoryKHR, vkCopyAccelerationStructureKHR, and vkCopyMemoryToAccelerationStructureKHR

  - removed `VkDeferredOperationInfoKHR` structure

  - change deferred host creation/return parameter behavior such that the implementation can modify such parameters until the deferred host operation completes

  - VK_KHR_deferred_host_operations is required again

- Change acceleration structure build to always be sized

  - de-alias VkAccelerationStructureMemoryRequirementsTypeNV and `VkAccelerationStructureMemoryRequirementsTypeKHR` and remove `VkAccelerationStructureMemoryRequirementsTypeKHR`

  - add vkGetAccelerationStructureBuildSizesKHR command and VkAccelerationStructureBuildSizesInfoKHR structure and `VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_BUILD_SIZES_INFO_KHR` enum to query sizes for acceleration structures and scratch storage

  - move size queries for scratch space to vkGetAccelerationStructureBuildSizesKHR

  - remove `compactedSize`, `buildFlags`, `maxGeometryCount`, `pGeometryInfos`, `pCreateSizeInfos` members of VkAccelerationStructureCreateInfoKHR and add the `size` member

  - add `maxVertex` member to VkAccelerationStructureGeometryTrianglesDataKHR structure

  - remove `VkAccelerationStructureCreateSizeInfoKHR` structure

(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:

  - VK_KHR_acceleration_structure (for acceleration structure operations)

  - VK_KHR_ray_tracing_pipeline (for ray tracing pipeline and shader stages)

  - VK_KHR_ray_query (for ray queries in existing shader stages)

- 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, 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 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 don’t 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 type 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 re-used. (!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 '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)

## See Also

VkAabbPositionsKHR, VkAccelerationStructureBuildGeometryInfoKHR, VkAccelerationStructureBuildRangeInfoKHR, VkAccelerationStructureBuildSizesInfoKHR, VkAccelerationStructureBuildTypeKHR, VkAccelerationStructureCompatibilityKHR, VkAccelerationStructureCreateFlagBitsKHR, VkAccelerationStructureCreateFlagsKHR, VkAccelerationStructureCreateInfoKHR, VkAccelerationStructureDeviceAddressInfoKHR, VkAccelerationStructureGeometryAabbsDataKHR, VkAccelerationStructureGeometryDataKHR, VkAccelerationStructureGeometryInstancesDataKHR, VkAccelerationStructureGeometryKHR, VkAccelerationStructureGeometryTrianglesDataKHR, VkAccelerationStructureInstanceKHR, VkAccelerationStructureKHR, VkAccelerationStructureTypeKHR, VkAccelerationStructureVersionInfoKHR, VkBuildAccelerationStructureFlagBitsKHR, VkBuildAccelerationStructureFlagsKHR, VkBuildAccelerationStructureModeKHR, VkCopyAccelerationStructureInfoKHR, VkCopyAccelerationStructureModeKHR, VkCopyAccelerationStructureToMemoryInfoKHR, VkCopyMemoryToAccelerationStructureInfoKHR, VkDeviceOrHostAddressConstKHR, VkDeviceOrHostAddressKHR, VkGeometryFlagBitsKHR, VkGeometryFlagsKHR, VkGeometryInstanceFlagBitsKHR, VkGeometryInstanceFlagsKHR, VkGeometryTypeKHR, VkPhysicalDeviceAccelerationStructureFeaturesKHR, VkPhysicalDeviceAccelerationStructurePropertiesKHR, VkTransformMatrixKHR, VkWriteDescriptorSetAccelerationStructureKHR, vkBuildAccelerationStructuresKHR, vkCmdBuildAccelerationStructuresIndirectKHR, vkCmdBuildAccelerationStructuresKHR, vkCmdCopyAccelerationStructureKHR, vkCmdCopyAccelerationStructureToMemoryKHR, vkCmdCopyMemoryToAccelerationStructureKHR, vkCmdWriteAccelerationStructuresPropertiesKHR, vkCopyAccelerationStructureKHR, vkCopyAccelerationStructureToMemoryKHR, vkCopyMemoryToAccelerationStructureKHR, vkCreateAccelerationStructureKHR, vkDestroyAccelerationStructureKHR, vkGetAccelerationStructureBuildSizesKHR, vkGetAccelerationStructureDeviceAddressKHR, vkGetDeviceAccelerationStructureCompatibilityKHR, vkWriteAccelerationStructuresPropertiesKHR

## Document Notes

For more information, see the Vulkan Specification

This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.

## Copyright

Copyright 2014-2021 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0