[Bf-committers] Proposal to Change Mathutils Vectors
Andrew Hale
trumanblending at gmail.com
Wed Dec 7 11:04:02 CET 2011
It should be noted that homogeneous coordinates are really a convenient
notation and do not adhere to the rules of vector arithmetic. They are
really the special case here and as noted by others, we already have
situations where pragmatic definitions are used in place of strict
mathematical correctness.
Thanks,
Andrew
On Wed, Dec 7, 2011 at 7:49 PM, Paul Melis <paul.melis at sara.nl> wrote:
> On 12/07/2011 07:25 AM, Peter K.H. Gragert wrote:
> > if A and B are matrices most of the cases A * B != B * A
> > Matrix multiplication is NOT commutative.
> >
> > Math:
> > Matrix * Vector (Vector should be a column vector)
> > Vector * Matrix (Vector should be a row vector)
> >
> > Could be done differently in Blender as it was from time to time, but
> then
> > it is not Math ..
>
> >>> v = Vector([1,2,3])
> >>> w = Vector([4,5,6])
> >>> v*w
> 32.0
>
> >>> w*v
> 32.0
>
> Vector * Vector also *just works*, completely disregarding the fact that
> one vector should be 1xN and the other Nx1 if you were to follow strict
> math conventions. 3D math in computer graphics has always been very
> pragmatic.
>
> Regards,
> Paul
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