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diff --git a/extern/draco/draco/src/draco/mesh/mesh_are_equivalent.h b/extern/draco/draco/src/draco/mesh/mesh_are_equivalent.h
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+// Copyright 2016 The Draco Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+#ifndef DRACO_MESH_MESH_ARE_EQUIVALENT_H_
+#define DRACO_MESH_MESH_ARE_EQUIVALENT_H_
+
+#include "draco/core/vector_d.h"
+#include "draco/mesh/mesh.h"
+
+// This file defines a functor to compare two meshes for equivalency up
+// to permutation of the vertices.
+namespace draco {
+
+// A functor to compare two meshes for equivalency up to permutation of the
+// vertices.
+class MeshAreEquivalent {
+ public:
+  // Returns true if both meshes are equivalent up to permutation of
+  // the internal order of vertices. This includes all attributes.
+  bool operator()(const Mesh &mesh0, const Mesh &mesh1);
+
+ private:
+  // Internal type to keep overview.
+  struct MeshInfo {
+    explicit MeshInfo(const Mesh &in_mesh) : mesh(in_mesh) {}
+    const Mesh &mesh;
+    std::vector<FaceIndex> ordered_index_of_face;
+    IndexTypeVector<FaceIndex, int> corner_index_of_smallest_vertex;
+  };
+
+  // Prepare functor for actual comparison.
+  void Init(const Mesh &mesh0, const Mesh &mesh1);
+
+  // Get position as Vector3f of corner c of face f.
+  static Vector3f GetPosition(const Mesh &mesh, FaceIndex f, int32_t c);
+  // Internal helper function mostly for debugging.
+  void PrintPosition(const Mesh &mesh, FaceIndex f, int32_t c);
+  // Get the corner index of the lex smallest vertex of face f.
+  static int32_t ComputeCornerIndexOfSmallestPointXYZ(const Mesh &mesh,
+                                                      FaceIndex f);
+
+  // Less compare functor for two faces (represented by their indices)
+  // with respect to their lex order.
+  struct FaceIndexLess {
+    explicit FaceIndexLess(const MeshInfo &in_mesh_info)
+        : mesh_info(in_mesh_info) {}
+    bool operator()(FaceIndex f0, FaceIndex f1) const;
+    const MeshInfo &mesh_info;
+  };
+
+  void InitCornerIndexOfSmallestPointXYZ();
+  void InitOrderedFaceIndex();
+
+  std::vector<MeshInfo> mesh_infos_;
+  int32_t num_faces_;
+};
+
+}  // namespace draco
+
+#endif  // DRACO_MESH_MESH_ARE_EQUIVALENT_H_