Subject:
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Re: ldglite (ldlite for OpenGL and Linux) new stuff
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sun, 6 Feb 2000 13:41:33 GMT
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Viewed:
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2858 times
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Paul:
> In lugnet.cad.dev, Jacob Sparre Andersen writes:
> > - Different coordinate systems
> >
> > I don't know how many there are, but since I find the choice
> > in LDraw strange, I can understand people that choose an
> > alternative in later programs (despite the sillyness of it).
>
> And earlier programs. BriCAD, L3G0, Ben's (?) POV library,
> VBLOCKs (an SGI GL program) and I think LegoPS (postscript)
> used different coordinates & units.
> Or at least they were all different from L3G0.
Yes (what a mess).
As a mathematician and physicist I prefer right-hand
rectangular coordinate systems with the first two
coordinates (x and y) in the plane and the last coordinate
(z) having the positive direction up. The units should (from
the physicist pov) of course be meters, even though the
minifig inside me tries to yell "deciLU".
> > - Naming conventions
> >
> > What other "naming" conventions than part numbers are used?
>
> L3G0 call a brick a "b2x4"; BriCAD called it a "b4x2"; LDRAW
> was the winner hands-down by using mold numbers.
Yes.
> > - Using POV "modellers"
> >
> > This sounds like a sensible possibility. I presume that they
> > are much more versatile than LEdit and the other LEGO
> > oriented CAD editors. Is that true?
>
> I've mentioned AC3D before. I have a DAT export module for
> this that I used with the Throwbot leg:
> http://www.lugnet.com/cad/dat/?n=154
> (The export module only works if you register AC3D):
> http://www.comp.lancs.ac.uk/computing/users/andy/ac3d.html
I have a certain dislike for Closed Source (CS) Software,
and I would certainly not advice that we become dependent on
a CS program, when many people are willing to spend time
developing a good Open Source (OS) solution.
> > We should also remember that even though POV is a good
> > raytracer, it is horrible for building instructions. We will
> > still need a tool that can convert our files to LEGO style
> > building instructions.
>
> I did some work in making instructions from a ray-tracer.
> See the instruction images at the bottom of:
> http://www.gyugyi.com/l3g0/darksun/L3/jade/outpost/outpost.html
They look ok. Will you reveal how you get POV to draw lines
at the edges?
> > If we choose to abandon the current LDraw editing tools and
> > switch to POV, we will need to write a renderer based on a
> > much more complicated file format (POV). This could be quite
> > difficult, and I suspect that making a LDraw "modeller"
> > would be easier than to make an instruction renderer that
> > reads POV files.
>
> Ah, but code to parse POV files already exists.
I know (in POV :-).
> True, the
> nesting of the transform matricies makes it had to tell
> what pixels correspond to the verticies of a triangle, but
> if you don't need to CSG, and ignore reflections, refractions,
> and lens distortions, you could make an LDLite-style z-buffer
> renderer for POV.
My main worry is how to identify which edges should be
rendered as lines and which shouldn't.
Another problem is how to handle the step-wise drawing on
building instructions we have in LDraw. I am not aware of
any file format, except for the LDraw (and LeoCAD) file
formats, that can handle this.
Play well,
Jacob
------------------------------------------------------------
-- E-mail: sparre@cats.nbi.dk --
-- Web...: <URL: http://hugin.ldraw.org/LEGO/Tog/ > --
------------------------------------------------------------
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Message has 2 Replies:
 | | Re: ldglite (ldlite for OpenGL and Linux) new stuff
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| (...) Another nice thing about LDraw type programs is that you see the model being built as it renders, unlike POV, where you just see the final image. --Bram Bram Lambrecht / o o \ BramL@juno.com ---...---oooo-----(_...o---...--- WWW: (URL) (25 years ago, 6-Feb-00, to lugnet.cad.dev)
| | | Re: ldglite (ldlite for OpenGL and Linux) new stuff
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| (...) Hmm. POV-Ray description files could possibly handle step-wise construction by playing with the timer (clock?), a feature used to produce animation files. I haven't played much with POV-Ray since I took up LDraw, especially not authoring (...) (25 years ago, 7-Feb-00, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: ldglite (ldlite for OpenGL and Linux) new stuff
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| Paul: [ Tells us that we are behaving a little bit silly. ] You are probably right, but... I think that the main problem is that practically none of us are experienced CAD developers or users. Some of Paul's points: - Different coordinate systems I (...) (25 years ago, 4-Feb-00, to lugnet.cad.dev)
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