 | | Re: Another matrix inverse question (and answer?)
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(...) Yes, that makes sense. Looking back at Travis's code, I see that's basically what's happening there, except that some references to the original matrix should be references to the inverse matrix. He probably used it only to invert rotations (...) (19 years ago, 11-Apr-07, to lugnet.cad)
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| | 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 (...) (19 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 (...) (19 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, (...) (19 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 (...) (19 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, (...) (19 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 (...) (19 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 (...) (19 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 (...) (19 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 (...) (19 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 (19 years ago, 10-Apr-07, to lugnet.cad.ldd)
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| | Re: Another matrix inverse question
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(...) Sorry about that. I wrote that code so long ago that I forgot that it wasn't a fully general-purpose matrix inversion routine. (Note that it is the way it is so that it will perform better, not because I was too lazy to do the whole shebang.) (...) (19 years ago, 10-Apr-07, to lugnet.cad)
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| | Re: Another matrix inverse question
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(...) I think you've converted Travis' code properly, but just looking at the code, I'd say it's only intended to produce the inverse of the upper-left 3x3 matrix. None of the other rows or the determinant depend in any way on the 4th row, and it's (...) (19 years ago, 10-Apr-07, to lugnet.cad)
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| | Another matrix inverse question
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Hello, I read James Reynolds' question about inverse matrices and the responses with interest since I similar questions about matrix inverses. I used Travis's TCVector::invertMatrix code as the base for a Java function. Other than the change to Java (...) (19 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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(...) I just uploaded my version 1.01e. This is what I have fixed and found as of today. I’m still working on some problem ones below and I’m at a loss on what to do if anything I could do. If you already downloaded the 1.01A through D you will have (...) (19 years ago, 10-Apr-07, to lugnet.cad.ldd)
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| | Re: POV Color Cheat! Turn Pink into Medium Blue
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(...) I thought it was, but in this case it wasn't. The color 24 line can be skipped. And the double pigment declaration was just a pure mistake; one definition is of course sufficient. :) /Tore (19 years ago, 9-Apr-07, to lugnet.cad.ray)
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| | Re: POV Color Cheat! Turn Pink into Medium Blue
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(...) Good to know. Thanks! (...) I kind of recall that. In some cases, I've seen that L3P ignores an LDraw file with just Type 0 lines. I haven't checked if the IFPOV code makes it not ignore C13-73.dat, but I just did it in a routine manner. /Tore (19 years ago, 9-Apr-07, to lugnet.cad.ray)
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| | Re: POV Color Cheat! Turn Pink into Medium Blue
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(...) If you want to see the medium blue in LDView, just add the following line to C13-73.dat (anywhere outside the IFPOV section): 0 !COLOUR Medium_Blue CODE 13 VALUE #6E99C8 EDGE 0 Tore, is the color 24 line in the file necessary in order to make (...) (19 years ago, 9-Apr-07, to lugnet.cad.ray)
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| | Re: POV Color Cheat! Turn Pink into Medium Blue [DAT]
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(...) This is a great idea that deserves to be highlighted while we're waiting for L3P and other programs to support ldconfig.ldr! Inpired be the objects like timers, dialog objects, menu items etc I add to a Form in a Delphi project, I just came up (...) (19 years ago, 9-Apr-07, to lugnet.cad.ray)
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| | Re: how does a line ends?
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(...) Now that I'm at work, I'm able to look at Microsoft's implementation of fgets for Visual Studio 2005. They do a lock on the file prior to their loop, then call _fgetc_nolock to get each character, instead of fgetc or fread. (That's an (...) (19 years ago, 9-Apr-07, to lugnet.cad, FTX)
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