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Diffstat (limited to 'transform.py')
| -rw-r--r-- | transform.py | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/transform.py b/transform.py index 1321c8c..ef8c96c 100644 --- a/transform.py +++ b/transform.py @@ -1,16 +1,24 @@ import numpy as np +def make_rotation_matrix(phi, n): + """ + Make the rotation matrix to rotate points through an angle `phi` + counter-clockwise around the axis `n` (when looking towards +infinity). + + Source: Weissten, Eric W. "Rotation Formula." Mathworld. + """ + n = np.asarray(n)/np.linalg.norm(n) + + return np.cos(phi)*np.identity(3) + (1-np.cos(phi))*np.outer(n,n) + \ + np.sin(phi)*np.array([[0,n[2],-n[1]],[-n[2],0,n[0]],[n[1],-n[0],0]]) + def rotate(x, phi, n): """ Rotate an array of points `x` through an angle phi counter-clockwise around the axis `n` (when looking towards +infinity). - - Source: Weisstein, Eric W. "Rotation Formula." Mathworld. """ x = np.asarray(x) - n = np.asarray(n)/np.linalg.norm(n) - r = np.cos(phi)*np.identity(3) + (1-np.cos(phi))*np.outer(n,n) + \ - np.sin(phi)*np.array([[0,n[2],-n[1]],[-n[2],0,n[0]],[n[1],-n[0],0]]) + r = make_rotation_matrix(phi, n) return np.inner(x,r) |