Method BuildRTAccelerationStructure

DXRPathTracer/DXRPathTracer.cpp:1389–1541

}

void DXRPathTracer::BuildRTAccelerationStructure()
{
    const FormattedBuffer& idxBuffer = currentModel->IndexBuffer();
    const StructuredBuffer& vtxBuffer = currentModel->VertexBuffer();

    const uint64 numMeshes = currentModel->NumMeshes();
    Array<D3D12_RAYTRACING_GEOMETRY_DESC> geometryDescs(numMeshes);

    const uint32 numGeometries = uint32(geometryDescs.Size());
    Array<GeometryInfo> geoInfoBufferData(numGeometries);

    for(uint64 meshIdx = 0; meshIdx < numMeshes; ++meshIdx)
    {
        const Mesh& mesh = currentModel->Meshes()[meshIdx];
        D3D12_RAYTRACING_GEOMETRY_DESC& geometryDesc = geometryDescs[meshIdx];
        geometryDesc = { };
        geometryDesc.Type = D3D12_RAYTRACING_GEOMETRY_TYPE_TRIANGLES;
        geometryDesc.Triangles.IndexBuffer = idxBuffer.GPUAddress + mesh.IndexOffset() * idxBuffer.Stride;
        geometryDesc.Triangles.IndexCount = uint32(mesh.NumIndices());
        geometryDesc.Triangles.IndexFormat = idxBuffer.Format;
        geometryDesc.Triangles.Transform3x4 = 0;
        geometryDesc.Triangles.VertexFormat = DXGI_FORMAT_R32G32B32_FLOAT;
        geometryDesc.Triangles.VertexCount = uint32(mesh.NumVertices());
        geometryDesc.Triangles.VertexBuffer.StartAddress = vtxBuffer.GPUAddress + mesh.VertexOffset() * vtxBuffer.Stride;
        geometryDesc.Triangles.VertexBuffer.StrideInBytes = vtxBuffer.Stride;
        geometryDesc.Flags = D3D12_RAYTRACING_GEOMETRY_FLAG_OPAQUE;

        GeometryInfo& geoInfo = geoInfoBufferData[meshIdx];
        geoInfo = { };
        geoInfo.VtxOffset = uint32(mesh.VertexOffset());
        geoInfo.IdxOffset = uint32(mesh.IndexOffset());
        geoInfo.MaterialIdx = mesh.MeshParts()[0].MaterialIdx;

        Assert_(mesh.NumMeshParts() == 1);
    }

    // Get required sizes for an acceleration structure
    D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAGS buildFlags = D3D12_RAYTRACING_ACCELERATION_STRUCTURE_BUILD_FLAG_PREFER_FAST_TRACE;

    D3D12_RAYTRACING_ACCELERATION_STRUCTURE_PREBUILD_INFO topLevelPrebuildInfo = {};

    {
        D3D12_BUILD_RAYTRACING_ACCELERATION_STRUCTURE_INPUTS prebuildInfoDesc = {};
        prebuildInfoDesc.DescsLayout = D3D12_ELEMENTS_LAYOUT_ARRAY;
        prebuildInfoDesc.Flags = buildFlags;
        prebuildInfoDesc.Type = D3D12_RAYTRACING_ACCELERATION_STRUCTURE_TYPE_TOP_LEVEL;
        prebuildInfoDesc.pGeometryDescs = nullptr;
        prebuildInfoDesc.NumDescs = 1;
        DX12::Device->GetRaytracingAccelerationStructurePrebuildInfo(&prebuildInfoDesc, &topLevelPrebuildInfo);
    }

    Assert_(topLevelPrebuildInfo.ResultDataMaxSizeInBytes > 0);

    D3D12_RAYTRACING_ACCELERATION_STRUCTURE_PREBUILD_INFO bottomLevelPrebuildInfo = {};

    {
        D3D12_BUILD_RAYTRACING_ACCELERATION_STRUCTURE_INPUTS prebuildInfoDesc = {};
        prebuildInfoDesc.DescsLayout = D3D12_ELEMENTS_LAYOUT_ARRAY;