 | | Re: Quick way to mirror-image a model? —Steve Bliss
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| | | (...) Would that work in general cases, or just for right-left reflection? (...) Actually, I think they're not - "Steve's algorithm" (ha!) requires that both the MP and ME transforms be mirroring, so that the MF transform would be non-mirroring. (...) (20 years ago, 23-Jun-04, to lugnet.cad)
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| | | | | Re: Quick way to mirror-image a model? —Carl Nelson
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| | | | | (...) It would need to determine the plane of reflection, and do the second reflection on the X components for left-right or Z components for front-back. (...) I've come up with the same results in all cases so far. I'll do some thinking as to which (...) (20 years ago, 23-Jun-04, to lugnet.cad)
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| | | | | Re: Quick way to mirror-image a model? —Carl Nelson
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| | | | (...) Can you or Don check my work? I'm trying to figure out why the ME transform that I did works in my program and the ME that Don put in mirror.ini works in his code, but not vice-versa. The most likely explanation is that I'm doing something (...) (20 years ago, 23-Jun-04, to lugnet.cad)
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| | | | | | Re: Quick way to mirror-image a model? —Don Heyse
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| | | | (...) Probably. ;^) (...) Matrix multiplication is not commutative. (distributive? Err, I forget my math terms.) You're doing one or more of the multiplications in the wrong order? Try ME * (MC * MP) instead. Notice I switched the order inside the (...) (20 years ago, 23-Jun-04, to lugnet.cad)
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| | | | | | Re: Quick way to mirror-image a model? —Carl Nelson
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| | | | (...) It's neither commutative [(a * b) * c != a * (b * c)] nor associative [a * b != b * a]. That shouldn't be the problem in the calculation above, since the current matrix was the identity matrix... (...) Looks like you're doing MF = MP * (MC * (...) (20 years ago, 23-Jun-04, to lugnet.cad)
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| | | | | | Re: Quick way to mirror-image a model? —Don Heyse
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| | | | (...) Yes, that looks right. The other thing that messes me up with LDRAW matrices is the row, column ordering. The ordering in LDRAW files is not what I would have chosen, so I always have to look it up. From the old FAQ: (URL) type 1's format is: (...) (20 years ago, 23-Jun-04, to lugnet.cad, lugnet.cad.mlcad)
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| | | | | | Re: Quick way to mirror-image a model? —Steve Bliss
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| | | | | (...) Total side note: I agree with Don, row/column ordering is not what I would have chosen. BUT, it is far easier (IMO) to hand-transform row/column LDraw commands than the equivalent column/row commands (like I've had to do in POV-Ray code). (...) (20 years ago, 23-Jun-04, to lugnet.cad, lugnet.cad.mlcad)
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| | | | | | Re: Quick way to mirror-image a model? —Michael Lachmann
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| | | | Hi Don, now it's getting interesting ... "Don Heyse" <dheyse@hotmail.spam....away.com> schrieb im Newsbeitrag news:HzrwBF.9t2@lugnet.com... <SNIP> (...) I'm actually reading it in as | a b c | | d e f | | g h i | and that is also how I'm writing my (...) (20 years ago, 24-Jun-04, to lugnet.cad, lugnet.cad.mlcad)
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