add normalize normals method

src/cpp/include/MeshBuilder.h

@@ -679,6 +679,7 @@ class MeshBuilder
     //   multimesh.push_back(surface_mesh);
     // }
     auto mesh = MeshProcessor::merge_meshes(multimesh, weld);
+    mesh.normalize_normal_direction();
     return mesh;
   }
 

src/cpp/include/Triangulate.h

@@ -134,7 +134,8 @@ static void call_triangle(Mesh &mesh,
     if (surface.vertices.size() == 3 && !has_holes)
     {
       mesh.vertices = surface.vertices;
-      mesh.faces.push_back(Simplex2D(0, 1, 2));
+      mesh.faces.push_back(Simplex2D(0, 1, 2, false));
+      mesh.sort_vertices();
       return;
     }
 
@@ -143,8 +144,9 @@ static void call_triangle(Mesh &mesh,
       mesh.vertices = surface.vertices;
       for (size_t i = 1; i < surface.vertices.size() - 1; i++)
       {
-        mesh.faces.push_back(Simplex2D(0, i, i + 1));
+        mesh.faces.push_back(Simplex2D(0, i, i + 1, false));
       }
+      mesh.sort_vertices();
     }
     else
     {

src/cpp/include/model/Mesh.h

@@ -44,12 +44,71 @@ class Mesh : public Printable
     return c;
   }
 
+  Vector3D centroid() const
+  {
+    Vector3D c{};
+    for (auto &v : vertices)
+    {
+      c += Vector3D(v);
+    }
+    c /= vertices.size();
+    return c;
+  }
+
+  /// sort vertices of each face
+  void sort_vertices(bool ccw = true)
+  {
+    for (auto &face : faces)
+    {
+      // Get the vertices of the face
+      auto v0 = vertices[face.v0];
+      auto v1 = vertices[face.v1];
+      auto v2 = vertices[face.v2];
+      auto normal = (v1 - v0).cross(v2 - v0);
+      // Check if the normal vector is pointing in the desired direction
+      bool swap = ccw ? normal.z < 0 : normal.z > 0;
+      if (swap) // Assuming z-axis is up
+      {
+        // Swap v1 and v2 to change the orientation
+        std::swap(face.v1, face.v2);
+      }
+    }
+  }
+
+  void normalize_normal_direction(bool outwards = true)
+  {
+    for (auto &face : faces)
+    {
+      auto centroid = this->centroid();
+      auto v0 = vertices[face.v0];
+      auto v1 = vertices[face.v1];
+      auto v2 = vertices[face.v2];
+      auto normal = (v1 - v0).cross(v2 - v0);
+      // Calculate the vector from the centroid to the face
+      auto to_face = (v0 + v1 + v2) / 3.0 - centroid;
+      bool swap = outwards ? normal.dot(to_face) < 0 : normal.dot(to_face) > 0;
+      if (swap)
+      {
+        // Swap v1 and v2 to change the orientation
+        std::swap(face.v1, face.v2);
+      }
+    }
+  }
+
+
+
+
+
+
+
   /// Pretty-print
   std::string __str__() const override
   {
     return "Mesh with " + str(vertices.size()) + " vertices and " +
            str(faces.size()) + " faces";
   }
+
+
 };
 
 } // namespace DTCC_BUILDER