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_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,
} VkBuildAccelerationStructureFlagBitsKHR;

or the equivalent

// Provided by VK_NV_ray_tracing
typedef VkBuildAccelerationStructureFlagBitsKHR VkBuildAccelerationStructureFlagBitsNV;

Description

  • VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_UPDATE_BIT_KHR indicates 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 .

  • VK_BUILD_ACCELERATION_STRUCTURE_ALLOW_COMPACTION_BIT_KHR indicates 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 indicates that the given acceleration structure build should prioritize trace performance over build time.

  • VK_BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_BUILD_BIT_KHR indicates that the given acceleration structure build should prioritize build time over trace performance.

  • VK_BUILD_ACCELERATION_STRUCTURE_LOW_MEMORY_BIT_KHR indicates 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.

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.

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 2014-2022 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0