r10050 - /1.3/maths_fns/rotation_matrix.py -- December 02, 2009 - 16:18

Author: bugman
Date: Wed Dec  2 16:18:53 2009
New Revision: 10050

URL: http://svn.gna.org/viewcvs/relax?rev=10050&view=rev
Log:
Bug fix for maths_fns.rotation_matrix.R_to_euler_zyz() for the case where 
beta = 0.

This uses the sub-matrix components of the z rotation to put the full 
rotation into alpha (gamma
is zero).


Modified:
    1.3/maths_fns/rotation_matrix.py

Modified: 1.3/maths_fns/rotation_matrix.py
URL: 
http://svn.gna.org/viewcvs/relax/1.3/maths_fns/rotation_matrix.py?rev=10050&r1=10049&r2=10050&view=diff
==============================================================================
--- 1.3/maths_fns/rotation_matrix.py (original)
+++ 1.3/maths_fns/rotation_matrix.py Wed Dec  2 16:18:53 2009
@@ -304,11 +304,21 @@
     # The beta Euler angle.
     beta = acos(R[2, 2])
 
-    # The alpha Euler angle.
-    alpha = atan2(R[2, 1], -R[2, 0])
-
-    # The gamma Euler angle.
-    gamma = atan2(R[1, 2], R[0, 2])
+    # Problem case - beta is zero so alpha and gamma are indistinguishable.
+    if R[2, 2] == 1.0:
+        # Put all the rotation into alpha.
+        alpha = atan2(R[1, 0], R[0, 0])
+
+        # Gamma.
+        gamma = 0.0
+
+    # Normal case.
+    else:
+        # The alpha Euler angle.
+        alpha = atan2(R[2, 1], -R[2, 0])
+
+        # The gamma Euler angle.
+        gamma = atan2(R[1, 2], R[0, 2])
 
     # Return the angles.
     return alpha, beta, gamma