Special:
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[DAT] (requires LDraw-compatible viewer)
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Subject:
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Re: Quick way to mirror-image a model?
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Newsgroups:
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lugnet.cad
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Date:
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Thu, 17 Jun 2004 19:52:27 GMT
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Viewed:
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2136 times
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In lugnet.cad, Carl Nelson wrote:
> In lugnet.cad, Dave Schuler wrote:
> > For simple mirroring of the parts from left-to-right. This only works for parts
> > oriented along the X, Y, and Z axes. If parts are rotated at odd angles (like
> > 30 degrees, or whatever), then this won't quite work, but it should get you
> > started.
> Dave, I tried your method in Excel and it appears to work with some caveats,
> though I don't really understand the column mappings:
>
> For left-to-right, you said to use columns D and G--that's corresponding to the
> Y position and the B rotation parameter. Shouldn't that be the X position and C
> parameter?
You know, I think you're correct about that. I think I'm the last person who
still uses LEdit as his primary LDraw platform, and for reasons of my own I
always orient my parts and models rotated 90 degrees relative to the true LDraw
standard orientation.
Maybe I should give a specific example of the default orientation, with the 2x4
brick at cursor position x=100, y=0, and z=-10. The letters correspond to the
Excel columns:
A B C D E F G H I J K L M N O P
1 16 100 0 -10 1 0 0 0 1 0 0 0 1 3001.DAT
The mirrored left-to-right, the line would read this way:
A B C D E F G H I J K L M N O P
1 16 100 0 -10 -1 0 0 0 1 0 0 0 -1 3001.DAT
If we're ignoring odd angles (30 degrees, or whatever) then the left-and-right
orientation will (should) always be governed by the G and O columns, and the
position will be goverend by columns D, E, and F.
. To mirror a part left-to-right, change the D, F, G, and O columns in the
mirror part to the negative values of the same columns in the original part.
I think that this corrects the omission of my earlier explanation. Depending on
your level of comfort with Excel (and depending also on the usefulness of my
explanation) you should be able to tweak all of the necessary cells fairly
easily.
> Parts such as slopes & 2 x 2 corners aren't in their correct orientation--any
> tips on how to get those right?
Sorry again about the omission--try it again with this new information that I
forgot to include before, and let me know if it works for you.
> (Actually, is there a tutorial on the rotation matrix anywhere? That might
> answer all my questions in one.)
That's a fine question. There are two very basic discussions of
orientation-in-space here:
http://www.ldraw.org/files/LDRAW.TXT
http://www.ldraw.org/files/LEDIT.TXT
Not bad as starting points, but they don't quite answer your question, either.
Good luck!
Dave!
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Message has 1 Reply:
 | | Re: Quick way to mirror-image a model? [DAT]
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| (...) Dumb, dumb, dumb. To be a true "mirror" as you've requested, the second example should have read this way: A B C D E F G H I J K L M N O P 1 16 -100 0 -10 -1 0 0 0 1 0 0 0 -1 3001.DAT The way I originally posted it, the 3001 brick would be (...) (20 years ago, 17-Jun-04, to lugnet.cad)
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Message is in Reply To:
| | Re: Quick way to mirror-image a model?
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| (...) Thanks for the responses--they were very helpful. I found the disadvantage to Don's rotation matrix method to be that when it's used the mouse commands in MLCad are reversed, i.e., dragging the part left moves it right--but it sure worked (...) (20 years ago, 17-Jun-04, to lugnet.cad)
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