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Re: Transformation matrix interface - pre-multiply/post-multiply definitions

From: Dirk Schulze <dschulze@adobe.com>
Date: Thu, 7 Mar 2013 20:57:02 -0800
To: Nikos Andronikos <nikos.andronikos@cisra.canon.com.au>
CC: "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <78BD7E84-C632-400C-A7C9-7FE7CA8252C9@adobe.com>

On Mar 7, 2013, at 8:06 PM, Nikos Andronikos <nikos.andronikos@cisra.canon.com.au> wrote:

> Hi Dirk,
> 
> I was having a look at the Matrix spec [1] and I believe the definitions for pre-multiply and post-multiply are backwards.
> 
> >From [1]:
> postmultiply
> Term B postmultiplied by term A is equal to A  B.
> From wikipedia [2]:
> post-multiply (or right multiply) A by C" means AC
> 
> Using B and A, as in your text this would give
> post-multiply (or right multiply) B by A" means BA
> 
> And likewise for pre-multiply.
> Could you check please?

One does not simply
define the order of pre/post-multiplication.

Fixed. Thanks!
Dirk

> 
> Cheers,
> Nikos
> 
> 1: https://dvcs.w3.org/hg/FXTF/raw-file/tip/matrix/index.html
> 2: http://en.wikipedia.org/wiki/Matrix_multiplication
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Received on Friday, 8 March 2013 04:57:30 GMT

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