# [SciPy-dev] [Numpy-discussion] A module for homogeneous transformation matrices, Euler angles and quaternions

Gareth Elston gareth.elston.floss@googlemail....
Wed Mar 11 18:07:19 CDT 2009

```Does anyone know any good internet references for defining and using
homogeneous transformation matrices, especially oblique projection
matrices? I'm writing some tests for transformations.py and I'm
getting unexpected results, quite possibly because I'm making naive
assumptions about how to use projection_matrix().

Thanks,
Gareth.

On Thu, Mar 5, 2009 at 3:28 AM, Jonathan Taylor
<jonathan.taylor@utoronto.ca> wrote:
> Looks cool but a lot of this should be done in an extension module to
> make it fast.  Perhaps starting this process off as a separate entity
> until stability is acheived.  I would be tempted to do some of this
> using cython.  I just wrote found that generating a rotation matrix
> from euler angles is about 10x faster when done properly with cython.
>
> J.
>
> On Wed, Mar 4, 2009 at 5:10 PM, Gareth Elston
> <gareth.elston.floss@googlemail.com> wrote:
>> I found a nice module for these transforms at
>> http://www.lfd.uci.edu/~gohlke/code/transformations.py.html . I've
>> been using an older version for some time and thought it might make a
>> good addition to numpy/scipy. I made some simple mods to the older
>> version to add a couple of functions I needed and to allow it to be
>> used with Python 2.4.
>>
>> The module is pure Python (2.5, with numpy 1.2 imported), includes
>> doctests, and is BSD licensed. Here's the first part of the module
>> docstring:
>>
>> """Homogeneous Transformation Matrices and Quaternions.
>>
>> A library for calculating 4x4 matrices for translating, rotating, mirroring,
>> scaling, shearing, projecting, orthogonalizing, and superimposing arrays of
>> homogenous coordinates as well as for converting between rotation matrices,
>> Euler angles, and quaternions.
>> """
>>
>> I'd like to see this added to numpy/scipy so I know I've got some
>> reading to do (scipy.org/Developer_Zone and the huge scipy-dev
>> discussions on Scipy development infrastructure / workflow) to make
>> sure it follows the guidelines, but where would people like to see
>> this? In numpy? scipy? scikits? elsewhere?
>>
>> I seem to remember that there was a first draft of a guide for
>> developers being written. Are there any links available?
>>
>> Thanks,
>> Gareth.
```

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