Structure specifying the geometry data used to build an acceleration structure.

Description

Only one of pGeometries or ppGeometries can be a valid pointer, the other must be NULL. Each element of the non-NULL array describes the data used to build each acceleration structure geometry.

The index of each element of the pGeometries or ppGeometries members of VkAccelerationStructureBuildGeometryInfoKHR is used as the geometry index during ray traversal. The geometry index is available in ray shaders via the RayGeometryIndexKHR built-in, and is used to determine hit and intersection shaders executed during traversal. The geometry index is available to ray queries via the OpRayQueryGetIntersectionGeometryIndexKHR instruction.

Setting BUILD_ACCELERATION_STRUCTURE_MOTION_BIT_NV in flags indicates that this build is a motion top level acceleration structure. A motion top level uses instances of format VkAccelerationStructureMotionInstanceNV if VkAccelerationStructureGeometryInstancesDataKHR::arrayOfPointers is FALSE.

If VkAccelerationStructureGeometryInstancesDataKHR::arrayOfPointers is TRUE, the pointer for each element of the array of instance pointers consists of 4 bits of VkAccelerationStructureMotionInstanceTypeNV in the low 4 bits of the pointer identifying the type of structure at the pointer. The device address accessed is the value in the array with the low 4 bits set to zero. The structure at the pointer is one of VkAccelerationStructureInstanceKHR, VkAccelerationStructureMatrixMotionInstanceNV or VkAccelerationStructureSRTMotionInstanceNV, depending on the type value encoded in the low 4 bits.

A top level acceleration structure with either motion instances or vertex motion in its instances must set BUILD_ACCELERATION_STRUCTURE_MOTION_BIT_NV in flags.

Members srcAccelerationStructure and dstAccelerationStructure may be the same or different for an update operation (when mode is BUILD_ACCELERATION_STRUCTURE_MODE_UPDATE_KHR). If they are the same, the update happens in-place. Otherwise, the target acceleration structure is updated and the source is not modified.

Valid Usage

• type must not be ACCELERATION_STRUCTURE_TYPE_GENERIC_KHR
• Only one of pGeometries or ppGeometries can be a valid pointer, the other must be NULL
• If type is ACCELERATION_STRUCTURE_TYPE_TOP_LEVEL_KHR, the geometryType member of elements of either pGeometries or ppGeometries must be GEOMETRY_TYPE_INSTANCES_KHR
• If type is ACCELERATION_STRUCTURE_TYPE_TOP_LEVEL_KHR, geometryCount must be 1
• If type is ACCELERATION_STRUCTURE_TYPE_BOTTOM_LEVEL_KHR the geometryType member of elements of either pGeometries or ppGeometries must not be GEOMETRY_TYPE_INSTANCES_KHR
• If type is ACCELERATION_STRUCTURE_TYPE_BOTTOM_LEVEL_KHR then the geometryType member of each geometry in either pGeometries or ppGeometries must be the same
• If type is ACCELERATION_STRUCTURE_TYPE_BOTTOM_LEVEL_KHR then geometryCount must be less than or equal to VkPhysicalDeviceAccelerationStructurePropertiesKHR::maxGeometryCount
• If type is ACCELERATION_STRUCTURE_TYPE_BOTTOM_LEVEL_KHR and the geometryType member of either pGeometries or ppGeometries is GEOMETRY_TYPE_AABBS_KHR, the total number of AABBs in all geometries must be less than or equal to VkPhysicalDeviceAccelerationStructurePropertiesKHR::maxPrimitiveCount
• If type is ACCELERATION_STRUCTURE_TYPE_BOTTOM_LEVEL_KHR and the geometryType member of either pGeometries or ppGeometries is GEOMETRY_TYPE_TRIANGLES_KHR, the total number of triangles in all geometries must be less than or equal to VkPhysicalDeviceAccelerationStructurePropertiesKHR::maxPrimitiveCount
• If flags has the BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_TRACE_BIT_KHR bit set, then it must not have the BUILD_ACCELERATION_STRUCTURE_PREFER_FAST_BUILD_BIT_KHR bit set
• If dstAccelerationStructure was created with ACCELERATION_STRUCTURE_CREATE_MOTION_BIT_NV set in VkAccelerationStructureCreateInfoKHR::flags, BUILD_ACCELERATION_STRUCTURE_MOTION_BIT_NV must be set in flags
• If BUILD_ACCELERATION_STRUCTURE_MOTION_BIT_NV is set in flags, dstAccelerationStructure must have been created with ACCELERATION_STRUCTURE_CREATE_MOTION_BIT_NV set in VkAccelerationStructureCreateInfoKHR::flags
• If BUILD_ACCELERATION_STRUCTURE_MOTION_BIT_NV is set in flags, type must not be ACCELERATION_STRUCTURE_TYPE_GENERIC_KHR
• If flags has the BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_UPDATE_EXT bit set then it must not have the BUILD_ACCELERATION_STRUCTURE_ALLOW_OPACITY_MICROMAP_DATA_UPDATE_EXT bit set

Valid Usage (Implicit)

• sType must be STRUCTURE_TYPE_ACCELERATION_STRUCTURE_BUILD_GEOMETRY_INFO_KHR
• pNext must be NULL
• type must be a valid VkAccelerationStructureTypeKHR value
• flags must be a valid combination of VkBuildAccelerationStructureFlagBitsKHR values
• If geometryCount is not 0, and pGeometries is not NULL, pGeometries must be a valid pointer to an array of geometryCount valid VkAccelerationStructureGeometryKHR structures
• If geometryCount is not 0, and ppGeometries is not NULL, ppGeometries must be a valid pointer to an array of geometryCount valid pointers to valid VkAccelerationStructureGeometryKHR structures
• Both of dstAccelerationStructure, and srcAccelerationStructure that are valid handles of non-ignored parameters must have been created, allocated, or retrieved from the same VkDevice

See Also

VkAccelerationStructureGeometryKHR, VkDeviceOrHostAddressKHR, BuildAccelerationStructuresKHR, CmdBuildAccelerationStructuresIndirectKHR, CmdBuildAccelerationStructuresKHR, GetAccelerationStructureBuildSizesKHR

Layout

struct VkAccelerationStructureBuildGeometryInfoKHR {
    VkStructureType sType;
    void const * pNext;
    VkAccelerationStructureTypeKHR type;
    VkBuildAccelerationStructureFlagsKHR flags;
    VkBuildAccelerationStructureModeKHR mode;
    VkAccelerationStructureKHR srcAccelerationStructure;
    VkAccelerationStructureKHR dstAccelerationStructure;
    uint32_t geometryCount;
    VkAccelerationStructureGeometryKHR const * pGeometries;
    VkAccelerationStructureGeometryKHR const * const * ppGeometries;
    VkDeviceOrHostAddressKHR scratchData;
}