Hi Charlie, I second your request for having a Xform.getMatrix() method that provides 3x4 Numeric array or tuple of tuples. I use this a good bit. My solution is to use the Chimera PDBmatrices.matrices module which deals with 3x4 matrices where the first 3 columns are the rotation and the last column is the translation. It's been in Chimera for the last couple years (with ocassional changes). Look at Python code chimera/share/PDBmatrices/matrices.py to see what is there. Example,
xf = chimera.Xform.zRotation(30) from PDBmatrices import matrices m = matrices.xform_matrix(xf) print m ((0.866025, -0.5, 0.0, 0.0), (0.5, 0.866025, 0.0, 0.0), (0.0, 0.0, 1.0, 0.0))
There is a chimera_xform() routine to go from matrix to Xform, and other routines to apply 3x4 matrices to points, or vectors, invert matrices, multiply matrices, .... Tom