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Re: quick comments on Matrix

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 15 Mar 2013 23:04:28 -0700
Message-ID: <CAAWBYDBUhc1nByAoArz_heinuVk8=hrQNan5PUonmbOmUK=wrQ@mail.gmail.com>
To: Gregg Tavares <gman@google.com>
Cc: "public-fx@w3.org" <public-fx@w3.org>, Dirk Schulze <dschulze@adobe.com>
On Fri, Mar 15, 2013 at 10:57 PM, Gregg Tavares <gman@google.com> wrote:
> I don't want to bikeshed here but in my limited circle a Point doesn't have
> a W. A Point represents a place in 2D or 3D space. Mathematically you can't
> add 2 points but you can add 2 vectors. Subtracting 2 points gives you a
> vector. Adding a vector to a point transforms a point. Adding 2 vectors
> gives another vector. That might just be my experience and not connected to
> any reality but I've seen the distinction in libraries I've used. It's also
> related the suggestion for transformPoint vs transformVector.

That's what the w indicates - if it's 0 it's a vector, if it's 1 it's a point.

~TJ
Received on Saturday, 16 March 2013 06:05:16 GMT

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