Mesh: add overloaded mesh decimation to set target number of triangles

src/Mod/Mesh/App/Core/Decimation.cpp

@@ -95,3 +95,52 @@ void MeshSimplify::simplify(float tolerance, float reduction)
 
     myKernel.Adopt(new_points, new_facets, true);
 }
+
+void MeshSimplify::simplify(int targetSize)
+{
+    Simplify alg;
+
+    const MeshPointArray& points = myKernel.GetPoints();
+    for (std::size_t i = 0; i < points.size(); i++) {
+        Simplify::Vertex v;
+        v.p = points[i];
+        alg.vertices.push_back(v);
+    }
+
+    const MeshFacetArray& facets = myKernel.GetFacets();
+    for (std::size_t i = 0; i < facets.size(); i++) {
+        Simplify::Triangle t;
+        for (int j = 0; j < 3; j++)
+            t.v[j] = facets[i]._aulPoints[j];
+        alg.triangles.push_back(t);
+    }
+
+    // Simplification starts
+    alg.simplify_mesh(targetSize, FLT_MAX);
+
+    // Simplification done
+    MeshPointArray new_points;
+    new_points.reserve(alg.vertices.size());
+    for (std::size_t i = 0; i < alg.vertices.size(); i++) {
+        new_points.push_back(alg.vertices[i].p);
+    }
+
+    std::size_t numFacets = 0;
+    for (std::size_t i = 0; i < alg.triangles.size(); i++) {
+        if (!alg.triangles[i].deleted)
+            numFacets++;
+    }
+    MeshFacetArray new_facets;
+    new_facets.reserve(numFacets);
+    for (std::size_t i = 0; i < alg.triangles.size(); i++) {
+        if (!alg.triangles[i].deleted) {
+            MeshFacet face;
+            face._aulPoints[0] = alg.triangles[i].v[0];
+            face._aulPoints[1] = alg.triangles[i].v[1];
+            face._aulPoints[2] = alg.triangles[i].v[2];
+            new_facets.push_back(face);
+        }
+    }
+
+    myKernel.Adopt(new_points, new_facets, true);
+}

src/Mod/Mesh/App/Core/Decimation.h

@@ -35,6 +35,7 @@ public:
     MeshSimplify(MeshKernel&);
     ~MeshSimplify();
     void simplify(float tolerance, float reduction);
+    void simplify(int targetSize);
 
 private:
     MeshKernel& myKernel;

src/Mod/Mesh/App/Mesh.cpp

@@ -989,6 +989,12 @@ void MeshObject::decimate(float fTolerance, float fReduction)
     dm.simplify(fTolerance, fReduction);
 }
 
+void MeshObject::decimate(int targetSize)
+{
+    MeshCore::MeshSimplify dm(this->_kernel);
+    dm.simplify(targetSize);
+}
+
 Base::Vector3d MeshObject::getPointNormal(unsigned long index) const
 {
     std::vector<Base::Vector3f> temp = _kernel.CalcVertexNormals();

src/Mod/Mesh/App/Mesh.h

@@ -217,6 +217,7 @@ public:
     void setPoint(unsigned long, const Base::Vector3d& v);
     void smooth(int iterations, float d_max);
     void decimate(float fTolerance, float fReduction);
+    void decimate(int targetSize);
     Base::Vector3d getPointNormal(unsigned long) const;
     std::vector<Base::Vector3d> getPointNormals() const;
     void crossSections(const std::vector<TPlane>&, std::vector<TPolylines> &sections,