Hi Phil,
If you have a reasonably recent version of the cctbx around (phenix, cci apps, maybe ccp4), try
this:
import scitbx.math
rotation_matrix = (1,0,0,0,0,1,0,-1,0)
fm = scitbx.math.r3_rotation_axis_and_angle_from_matrix(r=rotation_matrix)
print fm.axis
print fm.angle(deg=True)
The implementation (with comments) is in scitbx/include/scitbx/math/r3_rotation.h
Ralf
----- Original Message ----
From: Phil Evans <[log in to unmask]>
To: [log in to unmask]
Sent: Tuesday, July 29, 2008 1:10:50 AM
Subject: [ccp4bb] Rotation axis
If I've go a superposition transformation (x' = Rx + t), as it happens
from a superposition in ccp4mg, how do I get the position & direction
of the rotation axis (to draw in a picture)?
I know that any (orthonormal) transformation can be represented as a
rotation about an axis + a screw translation along that axis
I'm sure I've done this before ...
thanks
Phil
|