Subject:
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Re: Line in the Sand
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Newsgroups:
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lugnet.cad.dev
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Date:
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Tue, 21 Dec 1999 15:50:53 GMT
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Viewed:
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2888 times
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In lugnet.cad.dev, Lars C. Hassing wrote:
> Mirroring is not a problem. It causes a "negative determinant matrix"
> which can be detected and adjusted for (by toggling winding).
> So matrix-inversions are not evil.
Matrix-inversions are not evil. But for some reason, using them to actually
invert subfiles is evil (as opposed to using INVERTNEXT to invert subfiles).
If I reallly needed an answer to this, I'd go read past messages. But I *do*
remember:
a) I originally thought INVERTNEXT was redundant, because inversions could be
handled by inverting matrices.
b) I was later convinced that INVERTNEXT was needed.
I don't remember *why* INVERTNEXT is needed. But I am sure it is needed.
Steve
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Message has 2 Replies:
 | | Re: Line in the Sand
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| Steve Bliss wrote ... (...) Is this a joke? You argue very well in "Inversion" in "Language Extension Functionality" about the 3D tube ;-) /Lars Sorry if I missed a pun. (24 years ago, 21-Dec-99, to lugnet.cad.dev)
| | | Re: Line in the Sand
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| (...) I do, it's because of those cases like an hollow cylindir DAT file is referenced by another DAT file. Since the cylinder is supposed to be define outwards, but you can use it to make the inside/outside of a stud (for example) and the if the (...) (24 years ago, 21-Dec-99, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: Line in the Sand [DAT]
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| Jacob Sparre Andersen wrote... (...) (snip) (...) Why? Are you thinking about 1 16 -4 0 0 0 0 0 0 0 4 1-4disc.dat The determinant is zero, which BTW causes POVRay to halt ("singular matrix"). L3P has to fix these matrices or POVRay would not render (...) (24 years ago, 20-Dec-99, to lugnet.cad.dev)
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