Subject:
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Re: Unusual View matrices in LDRAW.INI
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Newsgroups:
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lugnet.cad.dev
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Date:
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Wed, 4 Oct 2000 18:33:50 GMT
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Viewed:
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606 times
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Don Heyse <dheyse@hotmail.spam.go.away.com> wrote:
> Wherever they came from, they don't seem to be pure rotation matrices
> fit for a viewing transformation. When I multiply one of these with
> another rotation matrix the model starts to look sheared.
I don't know their origin, but you're right, there's a shear component in
them. Here's what a matrix decomposition shows:
> Oblique=1,0,1,0.5,1,-0.5,-1,0,1
Scale : (1.5, 0.942809, 1.41421, 0)
Rotate : (0.321751, 0.729728, 0.463648, 0)
Translate : (0, 0, 0, 0)
Shear : (0.353553, -0.117851, -0.333333, 0)
> UpsideDown=-1,0,1,-0.5,-1,-0.5,1,0,0
Scale : (1.5, 0.942809, 0.707107, 0)
Rotate : (-0.321751, -0.729728, -2.67795, 0)
Translate : (0, 0, 0, 0)
Shear : (0.353553, -0.707107, 1, 0)
> Natural=0.625,0,1.075,0.5375,1.25,-0.3125,-1.25,0,2.5
Scale : (1.49734, 1.16669, 2.07954, 0)
Rotate : (0.622665, 0.987793, 0.710271, 0)
Translate : (0, 0, 0, 0)
Shear : (0.384604, -0.841771, 0.162744, 0)
(Note for purists: I'm not even sure I used the right matrix orientation to
get the above results, but there's a shear component in there either way.)
I look forward to the next update of ldglite - very useful program!
Steve
--
Barb & Steve Demlow | demlow@visi.com | www.visi.com/~demlow/
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Message has 1 Reply:
 | | Re: Unusual View matrices in LDRAW.INI
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| I knew there was a way to decompose the matrices! But I couldn't find it. Where is that written down? I also thought there was a way to remove the cumulative round off errors in a transformation matrix after many matrix multiplications. Do you (...) (24 years ago, 4-Oct-00, to lugnet.cad.dev)
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Message is in Reply To:
| | Unusual View matrices in LDRAW.INI
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| Hey, does anybody out there know the origin of the "Oblique", "UpsideDown", and "Natural" viewing matrices in LDRAW.INI. I'm not sure whether these came from LDAO, LDLITE, or perhaps even LDRAW? Wherever they came from, they don't seem to be pure (...) (24 years ago, 4-Oct-00, to lugnet.cad.dev)
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