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 17:59:32 GMT
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Viewed:
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1479 times
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In lugnet.cad.ray, Mike Thorn wrote:
> I knew about the model center comment at the end of the pov file, but I think
> I'm lost about the rest.
>
> Where should the translates and rotation be inserted? What do they do that makes
> the camera's movement different?
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.
--Travis Cobbs
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Message has 1 Reply:
 | | Re: A different simple question
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| (...) [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 (...) (21 years ago, 29-Jan-04, to lugnet.cad.ray)
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Message is in Reply To:
| | Re: A different simple question
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| (...) I am most definitely leaving myself out of that category. Especially after I see the stupid questions I'm going to have to ask here. (...) I thought that was what I was supposed to do...? (...) Right. I thought that's what rotating through the (...) (21 years ago, 29-Jan-04, to lugnet.cad.ray)
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