ComputeMeshlets

Computes meshlets from mesh subsets for use with DirectX 12 Mesh Shaders.

Computing meshlets for a single submesh:

HRESULT ComputeMeshlets(
    const uint16_t* indices, size_t nFaces,
    const XMFLOAT3* positions, size_t nVerts,
    const uint32_t* adjacency,
    std::vector<Meshlet>& meshlets,
    std::vector<uint8_t>& uniqueVertexIndices,
    std::vector<MeshletTriangle>& primitiveIndices,
    size_t maxVerts = MESHLET_DEFAULT_MAX_VERTS,
    size_t maxPrims = MESHLET_DEFAULT_MAX_PRIMS);
HRESULT ComputeMeshlets(
    const uint32_t* indices, size_t nFaces,
    const XMFLOAT3* positions, size_t nVerts,
    const uint32_t* adjacency,
    std::vector<Meshlet>& meshlets,
    std::vector<uint8_t>& uniqueVertexIndices,
    std::vector<MeshletTriangle>& primitiveIndices,
    size_t maxVerts = MESHLET_DEFAULT_MAX_VERTS,
    size_t maxPrims = MESHLET_DEFAULT_MAX_PRIMS);

Computing meshlets for multiple subsets of a mesh:

HRESULT ComputeMeshlets(
    const uint16_t* indices, size_t nFaces,
    const XMFLOAT3* positions, size_t nVerts,
    const std::pair<size_t, size_t>* indexSubsets, size_t nSubsets,
    _In_reads_opt_(nFaces * 3) const uint32_t* adjacency,
    std::vector<Meshlet>& meshlets,
    std::vector<uint8_t>& uniqueVertexIndices,
    std::vector<MeshletTriangle>& primitiveIndices,
    std::pair<size_t, size_t>* meshletSubsets,
    size_t maxVerts = MESHLET_DEFAULT_MAX_VERTS,
    size_t maxPrims = MESHLET_DEFAULT_MAX_PRIMS);
HRESULT __cdecl ComputeMeshlets(
    const uint32_t* indices, size_t nFaces,
    const XMFLOAT3* positions, size_t nVerts,
    const std::pair<size_t, size_t>* subsets, size_t nSubsets,
    const uint32_t* adjacency,
    std::vector<Meshlet>& meshlets,
    std::vector<uint8_t>& uniqueVertexIndices,
    std::vector<MeshletTriangle>& primitiveIndices,
    std::pair<size_t, size_t>* meshletSubsets,
    size_t maxVerts = MESHLET_DEFAULT_MAX_VERTS,
    size_t maxPrims = MESHLET_DEFAULT_MAX_PRIMS);

Parameters

adjacency can be nullptr, in which case it will call GenerateAdjacencyAndPointReps internally.

The computed meshlets are returned in meshlets, uniqueVertexIndices, and primitiveIndices.

The uniqueVertexIndices parameter is a byte buffer. The contents are uint16_t for the 16-bit indices input or uint32_t for 32-bit indices input.

The maxVerts value controls the maximum number of vertices per meshlet, and must be in the range MESHLET_MINIMUM_SIZE (32) to MESHLET_MAXIMUM_SIZE (256). The default value is MESHLET_DEFAULT_MAX_VERTS is 128.

The maxPrims value controls the maximum number of primitives per meshlet, and must be in the range MESHLET_MINIMUM_SIZE (32) to MESHLET_MAXIMUM_SIZE (256). The default value is MESHLET_DEFAULT_MAX_PRIMS is 128.

For the multisubset versions, meshletSubsets provides data in the same form as ComputeSubsets.

Remarks

Example

auto mesh = std::make_unique<WaveFrontReader<uint16_t>>();

if ( FAILED( mesh->Load( L"test.obj" ) ) )
   // Error

size_t nFaces = mesh->indices.size() / 3;
size_t nVerts = mesh->vertices.size();

std::unique_ptr<XMFLOAT3[]> pos( new XMFLOAT3[ nVerts ] );
for( size_t j = 0; j < nVerts; ++j )
   pos[ j ] = mesh->vertices[ j ].position;

std::vector<Meshlet> meshlets;
std::vector<uint8_t> uniqueVertexIndices;
std::vector<MeshletTriangle> primitiveIndices;
if ( FAILED( ComputeMeshlets( mesh->indices.data(), nFaces,
    pos.get(), nVerts,
    nullptr,
    meshlets, uniqueVertexIndices, primitiveIndices) )
    // Error

auto ib = reinterpret_cast<const uint16_t*>(uniqueVertexIndices.data());
size_t count = uniqueVertexIndices.size() / sizeof(uint16_t);