diff --git a/city_model_structure/attributes/polyhedron.py b/city_model_structure/attributes/polyhedron.py
index 7996b106..4f30ecf5 100644
--- a/city_model_structure/attributes/polyhedron.py
+++ b/city_model_structure/attributes/polyhedron.py
@@ -105,12 +105,9 @@ class Polyhedron:
     return (Surface(triangle_left, remove_last=False), Surface(rest_points_left, remove_last=False)), \
            (Surface(triangle_right, remove_last=False), Surface(rest_points_right, remove_last=False))
 
-  def _print(self, surface):
-    for point in surface.points:
-      print(point[0]-surface.min_x, point[1]-surface.min_y, point[2]-surface.min_z)
-
   def _triangulate(self, surface):
     triangles = []
+    complementary_surface = None
     triangles_count = len(surface.points) - 2
     points_list = surface.points_list
     point_index = 0
@@ -126,18 +123,21 @@ class Polyhedron:
         point_index = 0
         triangles.append(left_direction[0])
         points_list = left_direction[1].points_list
+        complementary_surface = left_direction[1]
       elif self._geometry.almost_same_area(area, right_area):
         area = right_direction[1].area
         point_index = 0
         triangles.append(right_direction[0])
         points_list = right_direction[1].points_list
+        complementary_surface = right_direction[1]
       else:
         point_index = point_index + 3
         if point_index > len(points_list):
           raise Exception('not ear found!')
       if len(points_list) == 9:
         # the rest point's are already a triangle
-        triangles.append(Surface(points_list, remove_last=False))
+        triangles.append(complementary_surface)
+
     return triangles
 
   @property
@@ -160,6 +160,7 @@ class Polyhedron:
           for sub_surface in sub_surfaces:
             face = []
             points = sub_surface.points
+            print(points)
             for point in points:
               face.append(self._position_of(point, face))
             self._faces.append(face)
@@ -172,6 +173,7 @@ class Polyhedron:
   @property
   def _polyhedron_mesh(self):
     if self._mesh is None:
+      print(self.faces)
       self._mesh = Trimesh(vertices=self.vertices, faces=self.faces)
     return self._mesh
 
@@ -272,12 +274,15 @@ class Polyhedron:
     return self._min_x
 
   @property
-  def centroid(self):
+  def center(self):
     """
     Polyhedron centroid
     :return: [x,y,z]
     """
-    return [self.max_x - self.min_x, self.max_y - self.min_y, self.max_z - self.min_z]
+    x = (self.max_x + self.min_x) / 2
+    y = (self.max_y + self.min_y) / 2
+    z = (self.max_z + self.min_z) / 2
+    return [x, y, z]
 
   def stl_export(self, full_path):
     """
diff --git a/city_model_structure/attributes/surface.py b/city_model_structure/attributes/surface.py
index 759091be..5ccd83c2 100644
--- a/city_model_structure/attributes/surface.py
+++ b/city_model_structure/attributes/surface.py
@@ -13,6 +13,8 @@ import math
 
 from helpers.geometry_helper import GeometryHelper
 
+# todo: remove pyny3d, seems to not be supported and has some issues
+
 
 class Surface:
   """
diff --git a/city_model_structure/city_object.py b/city_model_structure/city_object.py
index e40872bb..3244fae9 100644
--- a/city_model_structure/city_object.py
+++ b/city_model_structure/city_object.py
@@ -66,7 +66,7 @@ class CityObject:
     """
     if self._polyhedron is None:
       self._polyhedron = Polyhedron(self.surfaces)
-    return self._polyhedron.centroid
+    return self._polyhedron.center
 
   def stl_export(self, path):
     """