[Numpy-discussion] Iterative Matrix Multiplication

Charles R Harris charlesr.harris@gmail....
Sun Feb 28 20:31:05 CST 2010

On Sun, Feb 28, 2010 at 5:53 PM, Ian Mallett <geometrian@gmail.com> wrote:

> Hi,
> I have a list of vec3 lists (e.g. [[1,2,3],[4,5,6],[7,8,9],...]). To every
> single one of the vec3 sublists, I am currently applying transformations.  I
> need to optimize this with numpy.
> To get proper results, as far as I can tell, the vec3 lists must be
> expressed as vec4s: [[1,2,3],[4,5,6],[7,8,9],...] ->
> [[1,2,3,1],[4,5,6,1],[7,8,9,1],...].   Each of these needs to be
> multiplied by either a translation matrix, or a rotation and translation
> matrix.
> I don't really know how to approach the problem . . .
As I understand it, you want *different* matrices applied to each vector?
There are generalized ufuncs, which I haven't tried, but for small vectors
there is a trick. Let's see... heck, gmane looks to be dead at the moment.
Anyway, I posted the method on the list here a couple of years ago and I'll
put up a link if I can find it when gmane comes back.

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