diff --git a/port/PyAssimp/pyassimp/helper.py b/port/PyAssimp/pyassimp/helper.py
index ccfd8d2b5..249a0f2ab 100644
--- a/port/PyAssimp/pyassimp/helper.py
+++ b/port/PyAssimp/pyassimp/helper.py
@@ -8,8 +8,9 @@ import os
 import ctypes
 from ctypes import POINTER
 import operator
-import numpy
-from numpy import linalg
+
+try: import numpy
+except: numpy = None
 
 import logging;logger = logging.getLogger("pyassimp")
 
@@ -45,20 +46,88 @@ def vec2tuple(x):
 def transform(vector3, matrix4x4):
     """ Apply a transformation matrix on a 3D vector.
 
-    :param vector3: a numpy array with 3 elements
-    :param matrix4x4: a numpy 4x4 matrix
+    :param vector3: array with 3 elements
+    :param matrix4x4: 4x4 matrix
     """
-    return numpy.dot(matrix4x4, numpy.append(vector3, 1.))
-
+    if numpy:
+        return numpy.dot(matrix4x4, numpy.append(vector3, 1.))
+    else:
+        m0,m1,m2,m3 = matrix4x4; x,y,z = vector3
+        return [
+            m0[0]*x + m0[1]*y + m0[2]*z + m0[3],
+            m1[0]*x + m1[1]*y + m1[2]*z + m1[3],
+            m2[0]*x + m2[1]*y + m2[2]*z + m2[3],
+            m3[0]*x + m3[1]*y + m3[2]*z + m3[3]
+            ]
+    
+def _inv(matrix4x4):
+    m0,m1,m2,m3 = matrix4x4
+    
+    det  =  m0[3]*m1[2]*m2[1]*m3[0] - m0[2]*m1[3]*m2[1]*m3[0] - \
+            m0[3]*m1[1]*m2[2]*m3[0] + m0[1]*m1[3]*m2[2]*m3[0] + \
+            m0[2]*m1[1]*m2[3]*m3[0] - m0[1]*m1[2]*m2[3]*m3[0] - \
+            m0[3]*m1[2]*m2[0]*m3[1] + m0[2]*m1[3]*m2[0]*m3[1] + \
+            m0[3]*m1[0]*m2[2]*m3[1] - m0[0]*m1[3]*m2[2]*m3[1] - \
+            m0[2]*m1[0]*m2[3]*m3[1] + m0[0]*m1[2]*m2[3]*m3[1] + \
+            m0[3]*m1[1]*m2[0]*m3[2] - m0[1]*m1[3]*m2[0]*m3[2] - \
+            m0[3]*m1[0]*m2[1]*m3[2] + m0[0]*m1[3]*m2[1]*m3[2] + \
+            m0[1]*m1[0]*m2[3]*m3[2] - m0[0]*m1[1]*m2[3]*m3[2] - \
+            m0[2]*m1[1]*m2[0]*m3[3] + m0[1]*m1[2]*m2[0]*m3[3] + \
+            m0[2]*m1[0]*m2[1]*m3[3] - m0[0]*m1[2]*m2[1]*m3[3] - \
+            m0[1]*m1[0]*m2[2]*m3[3] + m0[0]*m1[1]*m2[2]*m3[3]
+        
+    return[[( m1[2]*m2[3]*m3[1] - m1[3]*m2[2]*m3[1] + m1[3]*m2[1]*m3[2] - m1[1]*m2[3]*m3[2] - m1[2]*m2[1]*m3[3] + m1[1]*m2[2]*m3[3]) /det,
+            ( m0[3]*m2[2]*m3[1] - m0[2]*m2[3]*m3[1] - m0[3]*m2[1]*m3[2] + m0[1]*m2[3]*m3[2] + m0[2]*m2[1]*m3[3] - m0[1]*m2[2]*m3[3]) /det,
+            ( m0[2]*m1[3]*m3[1] - m0[3]*m1[2]*m3[1] + m0[3]*m1[1]*m3[2] - m0[1]*m1[3]*m3[2] - m0[2]*m1[1]*m3[3] + m0[1]*m1[2]*m3[3]) /det,
+            ( m0[3]*m1[2]*m2[1] - m0[2]*m1[3]*m2[1] - m0[3]*m1[1]*m2[2] + m0[1]*m1[3]*m2[2] + m0[2]*m1[1]*m2[3] - m0[1]*m1[2]*m2[3]) /det],
+           [( m1[3]*m2[2]*m3[0] - m1[2]*m2[3]*m3[0] - m1[3]*m2[0]*m3[2] + m1[0]*m2[3]*m3[2] + m1[2]*m2[0]*m3[3] - m1[0]*m2[2]*m3[3]) /det,
+            ( m0[2]*m2[3]*m3[0] - m0[3]*m2[2]*m3[0] + m0[3]*m2[0]*m3[2] - m0[0]*m2[3]*m3[2] - m0[2]*m2[0]*m3[3] + m0[0]*m2[2]*m3[3]) /det,
+            ( m0[3]*m1[2]*m3[0] - m0[2]*m1[3]*m3[0] - m0[3]*m1[0]*m3[2] + m0[0]*m1[3]*m3[2] + m0[2]*m1[0]*m3[3] - m0[0]*m1[2]*m3[3]) /det,
+            ( m0[2]*m1[3]*m2[0] - m0[3]*m1[2]*m2[0] + m0[3]*m1[0]*m2[2] - m0[0]*m1[3]*m2[2] - m0[2]*m1[0]*m2[3] + m0[0]*m1[2]*m2[3]) /det],
+           [( m1[1]*m2[3]*m3[0] - m1[3]*m2[1]*m3[0] + m1[3]*m2[0]*m3[1] - m1[0]*m2[3]*m3[1] - m1[1]*m2[0]*m3[3] + m1[0]*m2[1]*m3[3]) /det,
+            ( m0[3]*m2[1]*m3[0] - m0[1]*m2[3]*m3[0] - m0[3]*m2[0]*m3[1] + m0[0]*m2[3]*m3[1] + m0[1]*m2[0]*m3[3] - m0[0]*m2[1]*m3[3]) /det,
+            ( m0[1]*m1[3]*m3[0] - m0[3]*m1[1]*m3[0] + m0[3]*m1[0]*m3[1] - m0[0]*m1[3]*m3[1] - m0[1]*m1[0]*m3[3] + m0[0]*m1[1]*m3[3]) /det,
+            ( m0[3]*m1[1]*m2[0] - m0[1]*m1[3]*m2[0] - m0[3]*m1[0]*m2[1] + m0[0]*m1[3]*m2[1] + m0[1]*m1[0]*m2[3] - m0[0]*m1[1]*m2[3]) /det],
+           [( m1[2]*m2[1]*m3[0] - m1[1]*m2[2]*m3[0] - m1[2]*m2[0]*m3[1] + m1[0]*m2[2]*m3[1] + m1[1]*m2[0]*m3[2] - m1[0]*m2[1]*m3[2]) /det,
+            ( m0[1]*m2[2]*m3[0] - m0[2]*m2[1]*m3[0] + m0[2]*m2[0]*m3[1] - m0[0]*m2[2]*m3[1] - m0[1]*m2[0]*m3[2] + m0[0]*m2[1]*m3[2]) /det,
+            ( m0[2]*m1[1]*m3[0] - m0[1]*m1[2]*m3[0] - m0[2]*m1[0]*m3[1] + m0[0]*m1[2]*m3[1] + m0[1]*m1[0]*m3[2] - m0[0]*m1[1]*m3[2]) /det,
+            ( m0[1]*m1[2]*m2[0] - m0[2]*m1[1]*m2[0] + m0[2]*m1[0]*m2[1] - m0[0]*m1[2]*m2[1] - m0[1]*m1[0]*m2[2] + m0[0]*m1[1]*m2[2]) /det]]
    
 def get_bounding_box(scene):
     bb_min = [1e10, 1e10, 1e10] # x,y,z
     bb_max = [-1e10, -1e10, -1e10] # x,y,z
-    return get_bounding_box_for_node(scene.rootnode, bb_min, bb_max, linalg.inv(scene.rootnode.transformation))
+    inv = numpy.linalg.inv if numpy else _inv
+    return get_bounding_box_for_node(scene.rootnode, bb_min, bb_max, inv(scene.rootnode.transformation))
 
 def get_bounding_box_for_node(node, bb_min, bb_max, transformation):
 
-    transformation = numpy.dot(transformation, node.transformation)
+    if numpy:
+        transformation = numpy.dot(transformation, node.transformation)
+    else:
+        t0,t1,t2,t3 = transformation
+        T0,T1,T2,T3 = node.transformation
+        transformation = [ [
+                t0[0]*T0[0] + t0[1]*T1[0] + t0[2]*T2[0] + t0[3]*T3[0],
+                t0[0]*T0[1] + t0[1]*T1[1] + t0[2]*T2[1] + t0[3]*T3[1],
+                t0[0]*T0[2] + t0[1]*T1[2] + t0[2]*T2[2] + t0[3]*T3[2],
+                t0[0]*T0[3] + t0[1]*T1[3] + t0[2]*T2[3] + t0[3]*T3[3]
+            ],[
+                t1[0]*T0[0] + t1[1]*T1[0] + t1[2]*T2[0] + t1[3]*T3[0],
+                t1[0]*T0[1] + t1[1]*T1[1] + t1[2]*T2[1] + t1[3]*T3[1],
+                t1[0]*T0[2] + t1[1]*T1[2] + t1[2]*T2[2] + t1[3]*T3[2],
+                t1[0]*T0[3] + t1[1]*T1[3] + t1[2]*T2[3] + t1[3]*T3[3]
+            ],[
+                t2[0]*T0[0] + t2[1]*T1[0] + t2[2]*T2[0] + t2[3]*T3[0],
+                t2[0]*T0[1] + t2[1]*T1[1] + t2[2]*T2[1] + t2[3]*T3[1],
+                t2[0]*T0[2] + t2[1]*T1[2] + t2[2]*T2[2] + t2[3]*T3[2],
+                t2[0]*T0[3] + t2[1]*T1[3] + t2[2]*T2[3] + t2[3]*T3[3]
+            ],[
+                t3[0]*T0[0] + t3[1]*T1[0] + t3[2]*T2[0] + t3[3]*T3[0],
+                t3[0]*T0[1] + t3[1]*T1[1] + t3[2]*T2[1] + t3[3]*T3[1],
+                t3[0]*T0[2] + t3[1]*T1[2] + t3[2]*T2[2] + t3[3]*T3[2],
+                t3[0]*T0[3] + t3[1]*T1[3] + t3[2]*T2[3] + t3[3]*T3[3]
+            ] ]
+    
     for mesh in node.meshes:
         for v in mesh.vertices:
             v = transform(v, transformation)