Subject:
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Re: A different simple question
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Newsgroups:
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lugnet.cad.ray
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Date:
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Thu, 29 Jan 2004 19:13:01 GMT
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Viewed:
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1872 times
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In lugnet.cad.ray, Travis Cobbs wrote:
> I'll try to explain it, but it's kind of a difficult concept to explain
> without pictures. Note that my explanation isn't based on POV, it's based
> on 3D computer graphics in general. In the real world, when you rotate
> something, you rotate it about some point. In 3D computer graphics, you
> can't do this directly. Rotations always happen around <0,0,0
> .
>
> This seems like a real problem, but fortunately it has a fairly easy fix.
> The fix is to just move the object you want to rotate so that its rotation
> point becomes <0,0,0>, then rotate, then move it back to its original >position.
>
> If you look at Lars' suggestion, you will see that he does just this. First,
> translate by the negation of the center point (thus moving the center point to
> <0,0,0>). Next, rotate. Finally, translate back.
>
> Note that the reason all of this is necessary is because L3P leaves the model in
> its original location (which is a good thing). While the L3P camera globe
> options may give the impression that the model has been moved so that its center
> is at <0,0,0>, this isn't actually the case. L3P performs the necessary
> calculations, and then places the camera at the appropriate place, without
> moving the actual model.
>
> Hope this helps.
[Lightbulb pops on]
Aaaahhhh!! :)
Now it all makes sense. So when the original model was created, it must not have
been at <0,0,0> in MLCAD.
With that in mind I checked out the coords and you all are absolutely right. I
picked out one of the places in the exact center of the bowl and it was in the
400's somewhere, not 0.
I don't see any reason why I can't just move the bowl to <0,0,0> in MLCAD and
try again, so I think I'll do that.
Thanks a lot for the clear explanation - and thanks for the tidied code, Steve!!
:)
If my computer is willing to cooperate perhaps I'll have something to show here
in a week or so. Rendering alone should take 2.3+ solid days on a 1.1Ghz
machine.
Thanks again - you've saved me a lot of headaches, especially future ones! I'll
remember to check the coordinates next time. :)
~Mike
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Message is in Reply To:
 | | Re: A different simple question
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| (...) I'll try to explain it, but it's kind of a difficult concept to explain without pictures. Note that my explanation isn't based on POV, it's based on 3D computer graphics in general. In the real world, when you rotate something, you rotate it (...) (21 years ago, 29-Jan-04, to lugnet.cad.ray)
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