fix bad normal calculation

utils.py

@@ -35,12 +35,30 @@ class attr_set():
 
 # --- Vector
 
-def triangle_normal(a, b, c):
-    x = a[1] * b[2] - a[2] * b[1]
-    y = a[2] * b[0] - a[0] * b[2]
-    z = a[0] * b[1] - a[1] * b[0]
-    
-    return np.array([x, y, z], dtype='float64')
+def triangle_normal(p1, p2, p3):
+    """
+    Calculate the normal of a triangle given its three vertices.
+
+    Parameters:
+    p1, p2, p3: the 3 vertices of the triangle
+
+    Returns:
+    mathutils.Vector: The normalized normal vector of the triangle.
+    """
+    ## Get edge vectors
+    edge1 = Vector(p2) - Vector(p1)
+    edge2 = Vector(p3) - Vector(p1)
+    ## Get normal (Cross product of the edge vectors)
+    normal = edge1.cross(edge2)
+    normal.normalize()
+    return normal
+
+## Bad normal calculation !!
+# def triangle_normal(a, b, c):
+#     x = a[1] * b[2] - a[2] * b[1]
+#     y = a[2] * b[0] - a[0] * b[2]
+#     z = a[0] * b[1] - a[1] * b[0]
+#     return np.array([x, y, z], dtype='float64')
 
 def plane_coords(size=1):
     v = size * 0.5