VkBuildAccelerationStructureFlagBitsKHR(3)

# VkBuildAccelerationStructureFlagBitsKHR(3) Manual Page

## Name

VkBuildAccelerationStructureFlagBitsKHR - Bitmask specifying additional parameters for acceleration structure builds

## C Specification

Bits which can be set in VkAccelerationStructureBuildGeometryInfoKHR::`flags` or VkAccelerationStructureInfoNV::`flags` specifying additional parameters for acceleration structure builds, are:

    // Provided by VK_KHR_acceleration_structure
    typedef enum VkBuildAccelerationStructureFlagBitsKHR {
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_UPDATE_BIT_KHR = 0x00000001,
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_COMPACTION_BIT_KHR = 0x00000002,
        VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_TRACE_BIT_KHR = 0x00000004,
        VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_BUILD_BIT_KHR = 0x00000008,
        VK_BUILD_ACCELERATION_STRUCTURE_LOW_MEMORY_BIT_KHR = 0x00000010,
      // Provided by VK_NV_ray_tracing_motion_blur
        VK_BUILD_ACCELERATION_STRUCTURE_MOTION_BIT_NV = 0x00000020,
      // Provided by VK_EXT_opacity_micromap
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_DATA_UPDATE_BIT_EXT = 0x00000100,
    #ifdef VK_ENABLE_BETA_EXTENSIONS
      // Provided by VK_NV_displacement_micromap
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISPLACEMENT_MICROMAP_UPDATE_BIT_NV = 0x00000200,
    #endif
      // Provided by VK_KHR_ray_tracing_position_fetch
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DATA_ACCESS_BIT_KHR = 0x00000800,
      // Provided by VK_NV_cluster_acceleration_structure
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_CLUSTER_OPACITY_MICROMAPS_BIT_NV = 0x00001000,
      // Provided by VK_KHR_opacity_micromap
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_UPDATE_BIT_KHR = 0x00000040,
      // Provided by VK_KHR_opacity_micromap
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISABLE_OPACITY_MICROMAPS_BIT_KHR = 0x00000080,
      // Provided by VK_KHR_opacity_micromap
        VK_BUILD_ACCELERATION_STRUCTURE_MICROMAP_LOSSY_BIT_KHR = 0x00000400,
      // Provided by VK_NV_ray_tracing
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_UPDATE_BIT_NV = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_UPDATE_BIT_KHR,
      // Provided by VK_NV_ray_tracing
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_COMPACTION_BIT_NV = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_COMPACTION_BIT_KHR,
      // Provided by VK_NV_ray_tracing
        VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_TRACE_BIT_NV = VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_TRACE_BIT_KHR,
      // Provided by VK_NV_ray_tracing
        VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_BUILD_BIT_NV = VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_BUILD_BIT_KHR,
      // Provided by VK_NV_ray_tracing
        VK_BUILD_ACCELERATION_STRUCTURE_LOW_MEMORY_BIT_NV = VK_BUILD_ACCELERATION_STRUCTURE_LOW_MEMORY_BIT_KHR,
      // Provided by VK_EXT_opacity_micromap
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_UPDATE_BIT_EXT = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_UPDATE_BIT_KHR,
      // Provided by VK_EXT_opacity_micromap
      // VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_UPDATE_EXT is a legacy alias
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_UPDATE_EXT = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_UPDATE_BIT_EXT,
      // Provided by VK_EXT_opacity_micromap
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISABLE_OPACITY_MICROMAPS_BIT_EXT = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISABLE_OPACITY_MICROMAPS_BIT_KHR,
      // Provided by VK_EXT_opacity_micromap
      // VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISABLE_OPACITY_MICROMAPS_EXT is a legacy alias
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISABLE_OPACITY_MICROMAPS_EXT = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISABLE_OPACITY_MICROMAPS_BIT_EXT,
      // Provided by VK_EXT_opacity_micromap
      // VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_DATA_UPDATE_EXT is a legacy alias
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_DATA_UPDATE_EXT = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_DATA_UPDATE_BIT_EXT,
    #ifdef VK_ENABLE_BETA_EXTENSIONS
      // Provided by VK_NV_displacement_micromap
      // VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISPLACEMENT_MICROMAP_UPDATE_NV is a legacy alias
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISPLACEMENT_MICROMAP_UPDATE_NV = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISPLACEMENT_MICROMAP_UPDATE_BIT_NV,
    #endif
      // Provided by VK_KHR_ray_tracing_position_fetch
      // VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DATA_ACCESS_KHR is a legacy alias
        VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DATA_ACCESS_KHR = VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DATA_ACCESS_BIT_KHR,
    } VkBuildAccelerationStructureFlagBitsKHR;

    // Provided by VK_NV_ray_tracing
    // Equivalent to VkBuildAccelerationStructureFlagBitsKHR
    typedef VkBuildAccelerationStructureFlagBitsKHR VkBuildAccelerationStructureFlagBitsNV;

## Description

- VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_UPDATE_BIT_KHR specifies that the specified acceleration structure can be updated with a `mode` of VK_BUILD_ACCELERATION_STRUCTURE_MODE_UPDATE_KHR in VkAccelerationStructureBuildGeometryInfoKHR or an `update` of VK_TRUE in vkCmdBuildAccelerationStructureNV . For sphere and LSS primitives, only positions and radii may be updated, the provided index buffers and flags must remain unchanged from the initial build.

- VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_COMPACTION_BIT_KHR specifies that the specified acceleration structure can act as the source for a copy acceleration structure command with `mode` of VK_COPY_ACCELERATION_STRUCTURE_MODE_COMPACT_KHR to produce a compacted acceleration structure.

- VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_TRACE_BIT_KHR specifies that the given acceleration structure build should prioritize trace performance over build time.

- VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_BUILD_BIT_KHR specifies that the given acceleration structure build should prioritize build time over trace performance.

- VK_BUILD_ACCELERATION_STRUCTURE_LOW_MEMORY_BIT_KHR specifies that this acceleration structure should minimize the size of the scratch memory and the final result acceleration structure, potentially at the expense of build time or trace performance.

- VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_UPDATE_BIT_KHR specifies that the opacity micromaps associated with the specified acceleration structure may change with an acceleration structure update.

- VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_DATA_UPDATE_BIT_EXT specifies that the data of the opacity micromaps associated with the specified acceleration structure may change with an acceleration structure update.

- VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISABLE_OPACITY_MICROMAPS_BIT_KHR specifies that the specified acceleration structure may be referenced in an instance with VK_GEOMETRY_INSTANCE_DISABLE_OPACITY_MICROMAPS_BIT_KHR set.

- VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_CLUSTER_OPACITY_MICROMAPS_BIT_NV specifies that opacity micromaps may be associated with the given cluster acceleration structure.

- VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DATA_ACCESS_BIT_KHR specifies that the specified acceleration structure can be used when fetching the vertex and radius positions of a hit LSS or sphere primitive, or vertex positions of a hit triangle.

- VK_BUILD_ACCELERATION_STRUCTURE_MICROMAP_LOSSY_BIT_KHR specifies that micromaps can be compressed with a lossy encoding as described in Ray Opacity Micromap, which may support additional subdivision levels.

- VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_DISPLACEMENT_MICROMAP_UPDATE_BIT_NV specifies that the displacement micromaps associated with the specified acceleration structure may change with an acceleration structure update.

Note | VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_UPDATE_BIT_KHR and VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_COMPACTION_BIT_KHR may take more time and memory than a normal build, and so should only be used when those features are needed.

Note | VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_UPDATE_BIT_KHR and VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_COMPACTION_BIT_KHR are allowed to be used together. In that case, the result of the compaction copy is used as the source of a build with `mode` of VK_BUILD_ACCELERATION_STRUCTURE_MODE_UPDATE_KHR to perform the compacted update.

## See Also

VK_KHR_acceleration_structure, VK_NV_ray_tracing, VkBuildAccelerationStructureFlagsKHR

## Document Notes

For more information, see the Vulkan Specification.

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright 2014-2026 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0