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Re: rotating an object around the center of a view

Subject: Re: rotating an object around the center of a view
From: Ken Tozier <email@hidden>
Date: Sun, 4 Mar 2007 15:01:04 -0500
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On Mar 4, 2007, at 2:59 PM, Erik Buck wrote:

Your solution seems workable but very strange to me.
Why rotate the "dial" instead of rotating the coordinate system in which the dial is drawn ?

Because the clock face and all it's parts are rendered in the same view. If I rotate the view coordinates, the whole clock rotates not just the hands.

Why invert and then re-invert the simple translation matrix ? Do you have some objection to the following ?
translateXBy: ox yBy: oy
rotateByDegrees: (timeInSeconds * -6.0f)
translateXBy: -ox yBy: -oy

Inverting the offset matrix does exactly the same thing without having to manually plug in the positive and negative x, y offsets before and after the rotate.

Ken
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References:
	>Re: rotating an object around the center of a view (From: Erik Buck <email@hidden>)

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