Subject:
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Re: rotation matrices
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Newsgroups:
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lugnet.cad.dat.parts
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Date:
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Wed, 18 Oct 2000 00:53:35 GMT
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Viewed:
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871 times
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"koen" <koen.jordens@student.kuleuven.ac.be> wrote in message
news:G2JIF8.L7o@lugnet.com...
> Hello,
> Does anyone have more information about those 9 numbers that make up the
> rotation matrix for a part in the dat file?
They are the upper-left 3x3 matrix of a standard 4x4 transformation matrix
used in 3D graphics. I'm not going to give a lesson on 3D transformations,
but if you find any references on 3D transformation matrices on the web (of
which there are plenty), an LDraw part specification maps like so:
1 <COLOR> X Y Z A B C D E F G H I part.dat
becomes:
A D G X
B E H Y
C F I Z
0 0 0 1
(Note the letters go vertically.) I believe some references may swap the
rows/columns, to produce:
A B C 0
D E F 0
G H I 0
X Y Z 1
It's easy to tell which matrix they are referring to by checking out where
the translation (X, Y, Z) portion fits into their matrix. Having mapped
LDraw models to OpenGL, I can say that any OpenGL-related texts will likely
use the first matrix.
I hope this helps.
(If I've somehow messed things up badly, someone please correct me.)
--Travis Cobbs (tcobbs@san.REMOVE.rr.com)
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Message has 1 Reply:
 | | Re: rotation matrices
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| (...) I'm pretty sure that should be: A D G 0 B E H 0 C F I 0 X Y Z 1 So multiplying (used fixed-pitch font for proper viewing): (x y z 1) (A D G 0) (B E H 0) (C F I 0) (X Y Z 1) gives (Ax + By + Cx + X Dx + Ey + Cz + Y Gx + Hy + Iz + Z 1) (...) (...) (24 years ago, 18-Oct-00, to lugnet.cad.dat.parts)
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Message is in Reply To:
| | rotation matrices [DAT]
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| Hello, Does anyone have more information about those 9 numbers that make up the rotation matrix for a part in the dat file? I would also like some information about edgelines. especially those found in axlehol8.dat since i'm using those measurements (...) (24 years ago, 16-Oct-00, to lugnet.cad.dat.parts)
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