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);
+}