 | | 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, (...) (17 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 (...) (17 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, (...) (17 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 (...) (17 years ago, 11-Apr-07, to lugnet.cad)
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| | 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 (...) (17 years ago, 11-Apr-07, to lugnet.cad)
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