diff --git a/mesh.h b/mesh.h
index e61e3b5..1f6ab6e 100644
--- a/mesh.h
+++ b/mesh.h
@@ -27,17 +27,17 @@ struct Mesh
     std::vector<Tangents> tangents;
     std::vector<Group> indiceGroups;
 
-    bool hasNormals()
+    bool hasNormals() const
     {
         return normals.size() != 0;
     }
 
-    bool hasTexCoords()
+    bool hasTexCoords() const
     {
         return texCoords.size() != 0;
     }
 
-    bool hasTangents()
+    bool hasTangents() const
     {
         return tangents.size() != 0;
     }
diff --git a/meshbuilder.cpp b/meshbuilder.cpp
index 0640898..a21b31d 100644
--- a/meshbuilder.cpp
+++ b/meshbuilder.cpp
@@ -1,5 +1,6 @@
 #include "meshbuilder.h"
 #include <glm/ext.hpp>
+#include <set>
 
 void MeshBuilder::addPosition(float x, float y, float z)
 {
@@ -81,6 +82,71 @@ int MeshBuilder::getNbGroups()
     return indiceGroups.size();
 }
 
+bool MeshBuilder::operator() (const int& vertId1, const int& vertId2) const
+{
+    if(positions[vertId1] != positions[vertId2])
+        return (positions[vertId1].x + positions[vertId1].y + positions[vertId1].z) > (positions[vertId2].x + positions[vertId2].y + positions[vertId2].z);
+    if(hasTexCoords())
+    {
+        if(texCoords[vertId1] != texCoords[vertId2])
+            return (texCoords[vertId1].x + texCoords[vertId1].y) > (texCoords[vertId2].x + texCoords[vertId2].y);
+    }
+    if(hasNormals())
+    {
+        if(normals[vertId1] != normals[vertId2])
+            return (normals[vertId1].x + normals[vertId1].y + normals[vertId1].z) > (normals[vertId2].x + normals[vertId2].y + normals[vertId2].z);
+    }
+    return false;
+}
+
+void MeshBuilder::mergeVertices()
+{
+    std::vector<int> swapped;
+    std::set<int, MeshBuilder> vertexSet;
+
+    int size = positions.size();
+
+    for(Group &g : indiceGroups)
+    for(int i=0; i<g.indices.size(); ++i)
+    {
+        std::pair<std::set<int,MeshBuilder>::iterator,bool> ret = vertexSet.insert(g.indices[i]);
+        if(!ret.second) // duplicate found
+        {
+            // updating indices references
+            int toDelete = g.indices[i];
+            swapped.push_back(toDelete);
+            g.indices[i] = *(ret.first);
+            // deleting the duplicate
+            positions[toDelete] = positions.back();
+            positions.pop_back();
+            if(hasTexCoords())
+            {
+                texCoords[toDelete] = texCoords.back();
+                texCoords.pop_back();
+            }
+            if(hasNormals())
+            {
+                normals[toDelete] = normals.back();
+                normals.pop_back();
+            }
+            if(hasTangents())
+            {
+                tangents[toDelete] = tangents.back();
+                tangents.pop_back();
+            }
+        }
+    }
+
+    fprintf(stdout, "found %d vertex duplicates\n", swapped.size());
+
+    for(Group &g : indiceGroups)
+    for(int i=0; i<g.indices.size(); ++i)
+    {
+        if(g.indices[i] >= positions.size())
+            g.indices[i] = swapped[size - g.indices[i]];
+    }
+}
+
 void MeshBuilder::computeNormals()
 {
     normals.resize(positions.size());
diff --git a/meshbuilder.h b/meshbuilder.h
index 90334fe..3487b3e 100644
--- a/meshbuilder.h
+++ b/meshbuilder.h
@@ -26,6 +26,9 @@ public:
     void setCurrentGroupMaterial(Material* myMaterial);
     int getNbGroups();
 
+    // merge same vertices
+    void mergeVertices();
+    bool operator() (const int& vertId1, const int& vertId2) const;
     // require positions and indices
     void computeNormals();
     // require normals and texCoord