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Subject: [ggl] Efficient rotation about a point
From: Lee (lee)
Date: 2009-11-29 14:27:16

Can a single matrix properly represent "-translate/rotate/+translate"?
I think the translation component of the matrix would be negated
resulting in rotation about the origin, losing the "rotation about a
point" behaviour. No?

Stephen Leary wrote:
> This is usually acomplished by producing a matrix that represents
> -translate/rotate/+translate then applying that matrix transform once.
> I havent checked to see if GGL supports matrix transforms but that is
> how i would approach this use case in "real life". The matrix gets
> built once and reused as many times as needed.
> Stephen
> On Sun, Nov 29, 2009 at 6:43 PM, Lee <lee_at_[hidden]
> <mailto:lee_at_[hidden]>> wrote:
> Hi,
> What is the best way (in terms of efficacy) to rotate a ring about
> a point in GGL?
> Looking at GGL it seems right now to require three separate passes
> over the point
> data: -translate/rotate/+translate. Can't this be done in some
> kind of single pass
> 'rotate_about_transformer'?

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