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Re: BafflinTransform

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On 10/5/2012 9:04 AM, Gene Wirchenko wrote:
> On Thu, 04 Oct 2012 11:44:05 -0700, markspace <-@.> wrote:
>
> [snip]
>
>> The method I'm used to from 3D graphics is to translate any objects back
>> to the origin, scale and rotate, then translate them back to their
>> original/intended point in space.  It's a literal three step process;
>> you can't put all that together in one matrix.
>
>       Yes, you can.  Start with an identity matrix and apply each of
> the three transforms in succession.  You now have one matrix which
> does all three transforms in one step.  Matrix multiplication is
> associative so this does work.


No, really it doesn't work this way.  Note I'm not talking about 
starting with the identity matrix.  I'm talking about starting with an 
object that's already been translated at least once.  You have to add an 
extra step to remove the translations back to the origin ("identity") or 
successive multiplications aren't going to work the way you'd expect.

And I don't think you can "pre-multiply" that out; you'll end up doing 
four, or more, operations instead of three.  In intensive graphics 
applications, that's a no-no.

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Thread

BafflinTransform bob smith <bob@coolfone.comze.com> - 2012-10-03 07:58 -0700
  Re: BafflinTransform markspace <-@.> - 2012-10-03 08:45 -0700
    Re: BafflinTransform Lew <lewbloch@gmail.com> - 2012-10-03 10:41 -0700
      Re: BafflinTransform Gene Wirchenko <genew@ocis.net> - 2012-10-03 10:51 -0700
      Re: BafflinTransform Arne Vajhøj <arne@vajhoej.dk> - 2012-10-03 21:36 -0400
        Re: BafflinTransform Gene Wirchenko <genew@ocis.net> - 2012-10-03 21:49 -0700
        Re: BafflinTransform Jeff Higgins <jeff@invalid.invalid> - 2012-10-04 03:26 -0400
          Re: BafflinTransform Gene Wirchenko <genew@ocis.net> - 2012-10-04 09:30 -0700
          Re: BafflinTransform Arne Vajhøj <arne@vajhoej.dk> - 2012-10-04 17:38 -0400
            Re: BafflinTransform Jeff Higgins <jeff@invalid.invalid> - 2012-10-05 03:00 -0400
              Re: BafflinTransform Arne Vajhøj <arne@vajhoej.dk> - 2012-10-05 22:02 -0400
        Re: BafflinTransform Lew <lewbloch@gmail.com> - 2012-10-04 12:05 -0700
    Re: BafflinTransform bob smith <bob@coolfone.comze.com> - 2012-10-04 07:22 -0700
      Re: BafflinTransform Gene Wirchenko <genew@ocis.net> - 2012-10-04 09:35 -0700
        Re: BafflinTransform "John B. Matthews" <nospam@nospam.invalid> - 2012-10-04 13:58 -0400
          Re: BafflinTransform markspace <-@.> - 2012-10-04 11:44 -0700
            Re: BafflinTransform "John B. Matthews" <nospam@nospam.invalid> - 2012-10-04 21:23 -0400
              Re: BafflinTransform markspace <-@.> - 2012-10-04 19:27 -0700
                Re: BafflinTransform Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-10-04 19:55 -0700
                Re: BafflinTransform Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-10-04 23:33 -0400
            Re: BafflinTransform Gene Wirchenko <genew@ocis.net> - 2012-10-05 09:04 -0700
              Re: BafflinTransform markspace <-@.> - 2012-10-05 09:34 -0700
                Re: BafflinTransform Gene Wirchenko <genew@ocis.net> - 2012-10-05 12:58 -0700
                Re: BafflinTransform markspace <-@.> - 2012-10-05 17:15 -0700
          Re: BafflinTransform Gene Wirchenko <genew@ocis.net> - 2012-10-04 13:51 -0700
  Re: BafflinTransform Jeff Higgins <jeff@invalid.invalid> - 2012-10-03 15:15 -0400
    Re: BafflinTransform Lew <lewbloch@gmail.com> - 2012-10-03 12:49 -0700
  Re: BafflinTransform Roedy Green <see_website@mindprod.com.invalid> - 2012-10-03 16:01 -0700

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