 | | Re: Another matrix inverse question
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(...) Som further clarification... I was back in the 3x3 matrix world when I wrote this: the true inverse of a rotation + translate in psuedo-4x4 notation is as follow [ R11 R12 R13 x R21 R22 R23 y R31 R32 R33 z 0 0 0 1 ] goes to [ R11 R21 R31 xp (...) (18 years ago, 11-Apr-07, to lugnet.cad)
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| | Re: Another matrix inverse question (and answer?)
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(...) If it's only rotations then it should make sense. Another way of passing the information is as follows (M,x) where M is the matrix and x is the translation vector the inverse of this is (Mi,-Mi x) which you can see by showing that an operation (...) (18 years ago, 11-Apr-07, to lugnet.cad)
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| | Re: Another matrix inverse question [DAT]
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(...) You might want to check your row/column order for the converted code from LDView. At least conceptually, I always invision transformation matrices like so: A B C X D E F Y G H I Z 0 0 0 1 Notice that the translation info is in the last column, (...) (18 years ago, 11-Apr-07, to lugnet.cad)
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| | Re: Another matrix inverse question (and answer?)
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(...) I think I just answered my own question. I applied the inverse rotation (calculated by swapping the off-diagonals) to the translation row of the original transformation and then negated it to get the translation row in the inverse. That worked (...) (18 years ago, 11-Apr-07, to lugnet.cad)
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| | Re: Another matrix inverse question
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(...) I can see the advantages of swapping the off-diagonals for inverting the rotation(s), but that still leaves the question of how to invert translations. In a current example I'm looking at, a minifig hand, the hand is rotated 45 degrees, (...) (18 years ago, 11-Apr-07, to lugnet.cad)
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| | Re: Another matrix inverse question
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(...) Quarternions are, IMO, a bad way to do what matrices do well. For a rotation you don't need to (and shouldn't) calculate the inverse by a routine. Just transpose (swap the off-diagonals) and you have the inverse. There's no point running (...) (18 years ago, 10-Apr-07, to lugnet.cad)
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| | Re: Another matrix inverse question
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Thanks for the information, everyone. Although the test case I posted was arbitrary, I did some other tests with matrices that were used for rotations and translations. The upper-left 3x3 seemed to be OK, but the bottom row had problems. I'm (...) (18 years ago, 10-Apr-07, to lugnet.cad)
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| | LSynth Service
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Hi, all. I've taken the liberty of fiddling around with the LSynth 2 source code a little bit more to create an LSynth Service, a text-processing extension for Mac OS X that lets you run LSynth just about anywhere you can edit text. The service (...) (18 years ago, 10-Apr-07, to lugnet.cad.dev.mac, lugnet.cad.dev, lugnet.cad)
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| | Re: Another matrix inverse question
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(...) Hi Travis, Looking at the java version of your inversion routine I would guess that it will work for almost any 3x3 matrix + 1x3 translation (the 4x3 + 1 form). Where it will have problems is in matrices for which one or more of the (...) (18 years ago, 10-Apr-07, to lugnet.cad)
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| | Re: NEW VERSION! Re: Conversion file for ldraw to ldd
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Hi Mike, Couple of ideas for a couple of the bugs. (...) Did you triy transparent and opaque? (...) Did you try 30039? (...) Tim (18 years ago, 10-Apr-07, to lugnet.cad.ldd)
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