# VkClusterAccelerationStructureBuildTriangleClusterInfoNV(3) Manual Page

## Name

VkClusterAccelerationStructureBuildTriangleClusterInfoNV - Parameters describing build operation for a cluster acceleration structure

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## C Specification

The VkClusterAccelerationStructureBuildTriangleClusterInfoNV structure is defined as:

    // Provided by VK_NV_cluster_acceleration_structure
    typedef struct VkClusterAccelerationStructureBuildTriangleClusterInfoNV {
        uint32_t                                                         clusterID;
        VkClusterAccelerationStructureClusterFlagsNV                     clusterFlags;
        uint32_t                                                         triangleCount:9;
        uint32_t                                                         vertexCount:9;
        uint32_t                                                         positionTruncateBitCount:6;
        uint32_t                                                         indexType:4;
        uint32_t                                                         opacityMicromapIndexType:4;
        VkClusterAccelerationStructureGeometryIndexAndGeometryFlagsNV    baseGeometryIndexAndGeometryFlags;
        uint16_t                                                         indexBufferStride;
        uint16_t                                                         vertexBufferStride;
        uint16_t                                                         geometryIndexAndFlagsBufferStride;
        uint16_t                                                         opacityMicromapIndexBufferStride;
        VkDeviceAddress                                                  indexBuffer;
        VkDeviceAddress                                                  vertexBuffer;
        VkDeviceAddress                                                  geometryIndexAndFlagsBuffer;
        VkDeviceAddress                                                  opacityMicromapArray;
        VkDeviceAddress                                                  opacityMicromapIndexBuffer;
    } VkClusterAccelerationStructureBuildTriangleClusterInfoNV;

## Members

- `clusterID` is a user specified identifier assigned to this cluster.

- `clusterFlags` is a bitmask of VkClusterAccelerationStructureClusterFlagBitsNV values describing flags how the cluster should be built.

- `triangleCount` is the number of triangles in this cluster.

- `vertexCount` is the number of unique vertices in this cluster.

- `positionTruncateBitCount` is the number of bits starting at the lowest bit (i.e. the LSBs of the mantissa), of each vertex position that will be truncated to zero to improve floating-point compression.

- `indexType` is a single VkClusterAccelerationStructureIndexFormatFlagBitsNV value specifying the index type in `indexBuffer`.

- `opacityMicromapIndexType` is a single VkClusterAccelerationStructureIndexFormatFlagBitsNV value specifying the index type in `opacityMicromapIndexBuffer`.

- `baseGeometryIndexAndGeometryFlags` is a VkClusterAccelerationStructureGeometryIndexAndGeometryFlagsNV value specifying the base geometry index and flags for all triangles in the cluster.

- `indexBufferStride` is the stride in bytes in `indexBuffer` with `0` meaning the values are tightly-packed.

- `vertexBufferStride` is the stride in bytes in `vertexBuffer` with `0` meaning the values are tightly-packed.

- `geometryIndexAndFlagsBufferStride` is the stride in bytes in `geometryIndexAndFlagsBuffer` with `0` meaning the values are tightly-packed.

- `opacityMicromapIndexBufferStride` is the stride in bytes in `opacityMicromapIndexBuffer` with `0` meaning the values are tightly-packed.

- `indexBuffer` contains the indices of vertices in the cluster and is of type `indexType`.

- `vertexBuffer` specifies the vertex data of the triangles in the cluster with format specified in VkClusterAccelerationStructureTriangleClusterInputNV::`vertexFormat`.

- `geometryIndexAndFlagsBuffer` is either `NULL` or an address containing strided VkClusterAccelerationStructureGeometryIndexAndGeometryFlagsNV values specifying the geometry index and flag for every triangle in the cluster.

- `opacityMicromapArray` is either `NULL` or specifies the address of a valid opacity micromap array to reference from the cluster acceleration structure. If it is `NULL`, then opacity micromaps will be disabled for this cluster acceleration structure.

- `opacityMicromapIndexBuffer` is either `NULL` or specifies the address of a strided array with size equal to the number of triangles or indices into the opacity micromap array.

## Description

The C language specification does not define the ordering of bit-fields, but in practice, this structure produces the correct layout with existing compilers. The intended bit pattern is the following:

- `triangleCount`, `vertexCount`, `positionTruncateBitCount`, `indexType` and `opacityMicromapIndexType` occupy the same memory as if a single `uint32_t` was specified in their place

  - `triangleCount` occupies the 9 least significant bits of that memory

  - `vertexCount` occupies the next 9 least significant bits of that memory

  - `positionTruncateBitCount` occupies the next 6 least significant bits of that memory

  - `indexType` occupies the next 4 least significant bits of that memory

  - `opacityMicromapIndexType` occupies the 4 most significant bits of that memory

If a compiler produces code that diverges from that pattern, applications must employ another method to set values according to the correct bit pattern.

Valid Usage

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-clusterID-10488
  `clusterID` must not be 0xFFFFFFFF

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-triangleCount-10489
  `triangleCount` must be less than or equal to VkPhysicalDeviceClusterAccelerationStructurePropertiesNV::`maxTrianglesPerCluster`

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-vertexCount-10490
  `vertexCount` must be less than or equal to VkPhysicalDeviceClusterAccelerationStructurePropertiesNV::`maxVerticesPerCluster`

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-indexType-10491
  `indexType` must only have a single bit set

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-opacityMicromapIndexType-10492
  `opacityMicromapIndexType` must only have a single bit set

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-positionTruncateBitCount-10493
  `positionTruncateBitCount` must be greater than or equal to VkClusterAccelerationStructureTriangleClusterInputNV::`minPositionTruncateBitCount` and less than or equal to `32`

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-indexBufferStride-10494
  `indexBufferStride` must be `0` or a multiple of `indexType`

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-vertexBufferStride-10495
  `vertexBufferStride` must be `0` or a multiple of value specified in VkClusterAccelerationStructureTriangleClusterInputNV::`vertexFormat`

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-baseGeometryIndex-10496
  The maximum geometry index after using the values in `baseGeometryIndex` and `geometryIndexBuffer` must be less than VkPhysicalDeviceClusterAccelerationStructurePropertiesNV::`maxClusterGeometryIndex`

Valid Usage (Implicit)

- VUID-VkClusterAccelerationStructureBuildTriangleClusterInfoNV-clusterFlags-parameter
  `clusterFlags` must be a valid combination of VkClusterAccelerationStructureClusterFlagBitsNV values

## See Also

VK_NV_cluster_acceleration_structure, VkClusterAccelerationStructureClusterFlagsNV, VkClusterAccelerationStructureGeometryIndexAndGeometryFlagsNV, VkDeviceAddress

## 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 2014-2025 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0