2010/3/1 Charles R Harris <charlesr.har...@gmail.com>: > On Sun, Feb 28, 2010 at 7:58 PM, Ian Mallett <geometr...@gmail.com> wrote: >> Excellent--and a 3D rotation matrix is 3x3--so the list can remain n*3. >> Now the question is how to apply a rotation matrix to the array of vec3? > > It looks like you want something like > > res = dot(vec, rot) + tran > > You can avoid an extra copy being made by separating the parts > > res = dot(vec, rot) > res += tran > > where I've used arrays, not matrices. Note that the rotation matrix > multiplies every vector in the array.
When you want to rotate a ndarray "list" of vectors: >>> a.shape (N, 3) >>> a [[1., 2., 3. ] [4., 5., 6. ]] by some rotation matrix: >>> rotation_matrix.shape (3, 3) where each row of the rotation_matrix represents one vector of the rotation target basis, expressed in the basis of the original system, you can do this by writing: >>> numpy.dot(a, rotations_matrix) , as Chuck pointed out. This gives you the rotated vectors in an ndarray "list" again: >>> numpy.dot(a, rotation_matrix).shape (N, 3) This is just somewhat more in detail what Chuck already stated > Note that the rotation matrix > multiplies every vector in the array. my 2 cents, Friedrich _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
