Method createDrawList

Source/Falcor/Scene/Scene.cpp:2692–2776

    }

    void Scene::createDrawList()
    {
        if (!mpMeshVao)
            return;

        // This function creates argument buffers for draw indirect calls to rasterize the scene.
        // The updateGeometryInstances() function must have been called before so that the flags are accurate.
        //
        // Note that we create four draw buffers to handle all combinations of:
        // 1) mesh is using 16- or 32-bit indices,
        // 2) mesh triangle winding is CW or CCW after transformation.
        //
        // TODO: Update the draw args if a mesh undergoes animation that flips the winding.

        mDrawArgs.clear();

        // Helper to create the draw-indirect buffer.
        auto createDrawBuffer = [this](const auto& drawMeshes, bool ccw, ResourceFormat ibFormat = ResourceFormat::Unknown)
        {
            if (drawMeshes.size() > 0)
            {
                DrawArgs draw;
                draw.pBuffer = mpDevice->createBuffer(sizeof(drawMeshes[0]) * drawMeshes.size(), ResourceBindFlags::IndirectArg, MemoryType::DeviceLocal, drawMeshes.data());
                draw.pBuffer->setName("Scene draw buffer");
                FALCOR_ASSERT(drawMeshes.size() <= std::numeric_limits<uint32_t>::max());
                draw.count = (uint32_t)drawMeshes.size();
                draw.ccw = ccw;
                draw.ibFormat = ibFormat;
                mDrawArgs.push_back(draw);
            }
        };

        if (hasIndexBuffer())
        {
            std::vector<DrawIndexedArguments> drawClockwiseMeshes[2], drawCounterClockwiseMeshes[2];

            uint32_t instanceID = 0;
            for (const auto& instance : mGeometryInstanceData)
            {
                if (instance.getType() != GeometryType::TriangleMesh) continue;

                const auto& mesh = mMeshDesc[instance.geometryID];
                bool use16Bit = mesh.use16BitIndices();

                DrawIndexedArguments draw;
                draw.IndexCountPerInstance = mesh.indexCount;
                draw.InstanceCount = 1;
                draw.StartIndexLocation = mesh.ibOffset * (use16Bit ? 2 : 1);
                draw.BaseVertexLocation = mesh.vbOffset;
                draw.StartInstanceLocation = instanceID++;

                int i = use16Bit ? 0 : 1;
                (instance.isWorldFrontFaceCW()) ? drawClockwiseMeshes[i].push_back(draw) : drawCounterClockwiseMeshes[i].push_back(draw);
            }

            createDrawBuffer(drawClockwiseMeshes[0], false, ResourceFormat::R16Uint);
            createDrawBuffer(drawClockwiseMeshes[1], false, ResourceFormat::R32Uint);
            createDrawBuffer(drawCounterClockwiseMeshes[0], true, ResourceFormat::R16Uint);