Subject:
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Re: LDraw File Format Spec 1.0 DRAFT - Call for Public Comments
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Newsgroups:
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lugnet.cad
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Date:
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Thu, 23 Aug 2007 01:02:21 GMT
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Viewed:
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5822 times
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--snip--
> > > Neither. It's just a question of wording. As long as you put the X, Y, and Z
> > > in the appropriate place (and the 0s in the other appropriate spots), and as
> > > long as you do your transformations correctly, both ways produce the same
> > > results.
> > >
> > > --Travis
> >
> > I think a full worked through example would do the specs a lot of good. If I
> > understand right the line
> >
> > 1 c x y z a b c d e f g h i part.dat
> >
> > transforms any point by the operation
> >
> > (u, v, w)->(x+a*u+b*v+c*w, y+d*u+e*v+f*w, z+g*u+h*v+i*w)
> >
> > With it spelled out explicitly like that a programmer can use whatever internal
> > format they like.
> >
> > Tim
>
> If I were new to 3D graphics (and I am ) I would be confused by this, I would
> have to ask someone else how to interpret the spec. I think Travis' proposal to
> show the two different matrices that can be built from the line of values is
> more clear than the equation. Like they say, a picture is worth a thousand
> words, or in this case, a big equation ;)
>
> Rob
I'm not new to matrices and Travis' example is still a little unrigorous which
is why I propose the mathematically sound form above. Note the amount of
discussion already here because of what people consider 'standard' or 'given'
forms of the matrices. The form I give is totally unambiguous.
Of course I'd like both ultimately.
Tim
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