Subject:
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Re: LPub4 Alpha3 available
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Newsgroups:
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lugnet.cad
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Date:
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Sat, 28 Jun 2008 03:13:52 GMT
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Viewed:
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6700 times
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In lugnet.cad, Tim David wrote:
> In lugnet.cad, Kevin L. Clague wrote:
> SNIP
> >
> > Are any of the matrix coefficients negative?
> >
> > Kev
>
> Had a look and yes. I'n not sure quite why though, the sub model in question
> consists of 2 headlight bricks side by side with a 1x2 grill tile across the two
> side studs. It is used with the grill facing out on both sides of a train it
> could be considered a mirror but at the same time it is also just a rotation.
Actually, the matrix can have negative coefficients without being a mirror. If
I remember correctly, mirror detection is a matter of checking if the
determinant of the matrix is positive or negative. If the determinant is
negative, then the matrix is a mirror matrix.
--Travis
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Message has 1 Reply:
 | | Re: LPub4 Alpha3 available
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| (...) You remember correctly. A 90 or 270 degree rotation will have a negative and positive coefficient off the diagonal while a 180 will have two negatives on the diagonal. Tim (16 years ago, 28-Jun-08, to lugnet.cad)
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Message is in Reply To:
| | Re: LPub4 Alpha3 available
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| In lugnet.cad, Kevin L. Clague wrote: SNIP (...) Had a look and yes. I'n not sure quite why though, the sub model in question consists of 2 headlight bricks side by side with a 1x2 grill tile across the two side studs. It is used with the grill (...) (16 years ago, 27-Jun-08, to lugnet.cad)
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