OK, I know I'm replying to myself, but the mail server here was down from Friday to Monday. I see Archie's response in the mailing list archives. I'm still not sure I understand why the rotation doesn't occur as I expect, but I see what you're talking about in the example.
So even though I don't entirely understand the problem, is there a solution? How can I rotate a non-uniformly scaled element around its center? Michael Bishop -----Original Message----- From: Bishop, Michael W. CONTR J9C880 [mailto:[EMAIL PROTECTED] Sent: Friday, December 16, 2005 4:18 PM To: [email protected] Subject: RE: Scaling around a center point... Well, when you rotate(t, x, y) you are rotating around the center point. What it does under the hood (if I understand correctly) is: Translate the coordinate system to x, y (the center point) Rotate (which should rotate around the above-mentioned center point) Translate back to the original coordinate system. I guess I don't see how axes come into play. I imagine a turntable. If the spindle is always the center point, it doesn't matter the shape of the object you're sticking on there, it should rotate around the center. I'm not even sure how I'd put something in the center of the ellipse; that'd be an entirely different element in my understanding. Michael Bishop -----Original Message----- From: Archie Cobbs [mailto:[EMAIL PROTECTED] Sent: Friday, December 16, 2005 3:37 PM To: [email protected] Subject: Re: Scaling around a center point... Bishop, Michael W. CONTR J9C880 wrote: > I don't understand why that would make a difference. Regardless of the > axis, the center point doesn't change, does it? > > -----Original Message----- > From: Archie Cobbs [mailto:[EMAIL PROTECTED] > Sent: Friday, December 16, 2005 3:10 PM > To: [email protected] > Subject: Re: Scaling around a center point... > > If you take a non-circular ellipse, then stretch it, you change its > apparent "axis". You are assuming that the ellipse's axis doesn't change > (an inferring rotation angle from it), but that's not true when you > stretch non-uniformly. Correct, the center point doesn't change... but what does that have to do with it? I don't understand your question. Try putting a big "R" in the middle of the ellipse or something so you can tell how much it *really* rotated and you'll see what I'm talking about. -Archie ________________________________________________________________________ __ Archie Cobbs * CTO, Awarix * http://www.awarix.com --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
