UE Mesh Generation and Editing at Runtime

UE Mesh Generation and Editing at Runtime

虚幻运行时和编辑器下生成和编辑 网格体。

UE Mesh

虚幻中常用的三种网格体

UProceduralMeshComponent 程序化网格体
UStaticMeshComponent 静态网格体
USimpleDynamicMeshComponent 动态网格体

借用他人总结的，UE4和UE5同样适用

USimpleDynamicMeshComponent支持运行时和编辑器下对网格体的编辑，UE5下新增的模型编辑功能使用的就是这个，支持布尔，支持编辑顶点、边和面，支持挤出等等几何操作。

• Hole Filling and Boolean Failure Handling 补洞
• Remeshing
• Mesh Booleans
• Mesh Morphological Operations and Mesh Simplification
• “Solidification” with the Fast Mesh Winding Number
• AABBTree Queries
• Import and Attributes (结合第三方库导入其他格式的模型，如obj，ply等等)

UE 插件

已经作为UE官方自带插件

集成第三方库libigl，可进行复杂的几何计算。
使用libigl对几何进行平滑操作（拉普拉斯平滑）

TUniqueFunction<void(FDynamicMesh3&)> UIGLSmoothingTool::MakeMeshProcessingFunction()
{
    // make local copies of current settings
    int SolveIterations = Properties->Iterations;
    float Smoothness = Properties->Smoothness;

    // construct compute lambda
    auto EditFunction = [Smoothness, SolveIterations](FDynamicMesh3& ResultMesh)
    {
        Eigen::MatrixXd V;      Eigen::MatrixXi F;    
        iglext::DynamicMeshToIGLMesh(ResultMesh, V, F);    // convert FDynamicMesh3 to igl mesh representation

        Eigen::SparseMatrix<double> L;
        igl::cotmatrix(V, F, L);    // Compute Laplace-Beltrami operator L

        Eigen::MatrixXd U = V;      // smoothed positions will be computed in U

        for (int k = 0; k < SolveIterations; ++k)
        {
            Eigen::SparseMatrix<double> M;     // Recompute mass matrix on each step
            igl::massmatrix(U, F, igl::MASSMATRIX_TYPE_BARYCENTRIC, M);

            const auto& S = (M - Smoothness * L);
            Eigen::SimplicialLLT<Eigen::SparseMatrix<double>> solver(S);
            U = solver.solve(M * U).eval();    // Solve (M-delta*L) U = M*U
        }
        
        iglext::SetVertexPositions(ResultMesh, U);   // copy updated positions back to FDynamicMesh3
    };

    return MoveTemp(EditFunction);  // return compute lambda
}

编辑器下平滑示例：

其他示例

GitHub相关仓库

参考

1、http://www.gradientspace.com/tutorials/2020/10/23/runtime-mesh-generation-in-ue426
2. http://www.gradientspace.com/tutorials/2020/9/21/command-line-geometry-processing-with-unreal-engine
3. https://blog.csdn.net/mrbaolong/article/details/132112714?spm=1001.2014.3001.5501
4. https://blog.csdn.net/mrbaolong/article/details/131543522?spm=1001.2014.3001.5501