Function BuildBVH

BakingLab/MeshBaker.cpp:699–801

Builds a BVH tree for an entire model/scene

// Builds a BVH tree for an entire model/scene
static void BuildBVH(const Model& model, BVHData& bvhData, ID3D11Device* d3dDevice, RTCDevice device)
{
    if(bvhData.Scene != nullptr)
    {
        rtcDeleteScene(bvhData.Scene);
        bvhData.Scene = nullptr;
    }
    bvhData.Scene = rtcDeviceNewScene(device, RTC_SCENE_DYNAMIC, RTC_INTERSECT1);
    bvhData.Device = device;

    // Count the total number of vertices and triangles
    uint32 totalNumVertices = 0;
    uint32 totalNumTriangles = 0;
    for(uint64 i = 0; i < model.Meshes().size(); ++i)
    {
        const Mesh& mesh = model.Meshes()[i];
        Assert_(mesh.VertexStride() == sizeof(Vertex));
        totalNumVertices += mesh.NumVertices();
        totalNumTriangles += mesh.NumIndices() / 3;
    }

    bvhData.Triangles.resize(totalNumTriangles);
    bvhData.Vertices.resize(totalNumVertices);
    bvhData.MaterialIndices.resize(totalNumTriangles);
    std::vector<Float4> vertices(totalNumVertices);

    uint32 vtxOffset = 0;
    uint32 triOffset = 0;

    // Add the data for each mesh
    for(uint64 meshIdx = 0; meshIdx < model.Meshes().size(); ++meshIdx)
    {
        const Mesh& mesh = model.Meshes()[meshIdx];
        const Vertex* vertexData = reinterpret_cast<const Vertex*>(mesh.Vertices());
        const uint8* indexData = mesh.Indices();
        const uint32 numVertices = mesh.NumVertices();
        const uint32 numIndices = mesh.NumIndices();
        const uint32 indexSize = mesh.IndexSize();
        const uint32 vertexStride = mesh.VertexStride();

        // Prepare the triangles
        const uint32 numTriangles = numIndices / 3;
        for(uint64 partIdx = 0; partIdx < mesh.MeshParts().size(); ++partIdx)
        {
            const MeshPart& meshPart = mesh.MeshParts()[partIdx];
            const uint32 startTriangle = meshPart.IndexStart / 3;
            const uint32 endTriangle = (meshPart.IndexStart + meshPart.IndexCount) / 3;
            for(uint32 i = startTriangle; i < endTriangle; ++i)
            {
                const uint32 idx0 = GetIndex(indexData, i * 3 + 0, indexSize) + vtxOffset;
                const uint32 idx1 = GetIndex(indexData, i * 3 + 1, indexSize) + vtxOffset;
                const uint32 idx2 = GetIndex(indexData, i * 3 + 2, indexSize) + vtxOffset;

                bvhData.Triangles[i + triOffset] = Uint3(idx0, idx1, idx2);
                bvhData.MaterialIndices[i + triOffset] = meshPart.MaterialIdx;
            }
        }