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From: nrossi@jarthur.Claremont.EDU (Nick Rossi)
Newsgroups: comp.sys.cbm
Subject: Re: Rotation in Two Dimensions, Dude!
Message-ID: <10097@jarthur.Claremont.EDU>
Date: 12 Dec 90 09:09:58 GMT
References: <90344.192136CMWOLF@MTUS5.BITNET>
Organization: Harvey Mudd College, Claremont, CA 91711
Lines: 22

In article <90344.192136CMWOLF@MTUS5.BITNET> CMWOLF@MTUS5.BITNET writes:
>Does anyone have a routine that would take a pixel block (e.g. a
>sprite) and rotate it?  I'd settle for something as simple as
>90 degrees, but would like to be at least able to do it in
>45 degree jumps, and would love to be able to do it in 1 degree
>jumps.  I have no idea how to start such an undertaking.
>I'll settle for any tips or ideas anyone might have.
>I'd also like to be able to rotate a block of pixels of different
>sizes, e.g. a user blocked (defined) area.

One brute-force way to do this would be to define coordinates for every
pixel in the block using an origin at the very center of the block.  Then
calculate new coordinates for each pixel by multiplying the x-coordinate
by the cosine of the rotation angle and the y-coordinate by the sine of the
angle.  This would be rather slow for larger blocks, but you might be able
to use this general approach to find a faster way of doing it.


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Nick Rossi, '93     | "That's nasty, Wyatt..."
Harvey Mudd College | "That's Chet, Gary!"
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