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 CAD / Development / Organizations / LDraw / 4123
4122  |  4124
Subject: 
Preparing a L(EGO)Draw part for the Parts Tracker – A review
Newsgroups: 
lugnet.cad, lugnet.cad.dat.parts, lugnet.cad.dev.org.ldraw
Followup-To: 
lugnet.cad.dat.parts
Date: 
Thu, 4 Oct 2007 13:14:47 GMT
Highlighted: 
! (details)
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When the Lego Universe Team has started to share rough data of 80 parts
http://www.ldraw.org/Article489.html and soon after I've got feedback from part
authors that because of their excellent quality those parts were heavyweights
and would give us a hard time reducing the file size I was curious to what
extend I could strip them down. After approx. 10 working hours my part was cut
by 92%.

After I had chosen the “44572.dat - Hinge Panel 2 x 4 x 3 & 1/3 Locking” from
the L(EGO)Draw parts chart at http://www.ldraw.org/Article490.html I added my
name to the chart (kind of easy with admin rights ;-) to let people know I was
working on the part.
First I compared the part with the similar and already certified „2582.dat -
Hinge Panel 2 x 4 x 3 & 1/3” in MLCad. I was wondering if the LEGO Universe Team
had done a good job on the overall size and orientation. The part was excellent
but to my amazement it had an offset of 0.4 LDU on the x axis and the studs were
way to small.

After correcting the position and substituting all the quads and edges building
the studs with the „stud2.dat - Stud Open“ primitive I tackled the section with
the Click-lock hinges. The click-locks created with the stl2dat conversion tool
were 0.25 LDU larger on the x-axis than our primitive „clh4.dat - Click-lock
hinge half dual finger for bricks and plates“ is (deside the fact that clh4.dat
makes usage of cylinder primitives to get a smoother look)!
We know that the source for the L(EGO)Draw parts are the original shapes,
created for the molding machines – in short they are the REFERENCE. A this point
I had to take a critical decision: fix the clh4.dat and all the parts using the
primitive (and there are quite a lot) in order to be faithful to the REFERENCE
or fix my part. I opted for the latter. I can live with a 0.1 mm tolerance – if
you cannot feel free to fix clh4.dat. As a side note it might interests you that
LEGO's part designers in Billund use Rhino http://www.rhino3d.com/ for
prototyping and not SolidWorks as suggested by the stl2dat conversion tools – as
I was told by the LEGO Master Builders present at the 1000SteineLand 2007 in
Berlin.
Using Syncedit http://news.lugnet.com/cad/?n=13926 (strangely it is not listed
on Anders' website) through LDDP I trimmed all the figures where the click-lock
primitives touch the body. Furthermore this involved deleting/fixing the
superfluous triangles and quads.

Back in MLCad the next step was getting rid off of 50% of the overall file size
by cutting the part in two and deleting one half of it. It was clear right from
the start that I would subfile most of the code to allow patterned versions and
since I can mirror the subpart using the matrix there was no need for an entire
part.

With the LDraw Primitives Reference http://www.ldraw.org/library/primref/ at
hand I once more looked out for portions of the part I could replace with boxes
and cylinders.

Finally I run the rest of the code through LDDP's Error Checking, fixed
non-coplanar quads or code with bad vertex sequence I had messed up when I cut
the part in two, sorted and BFCed the part by polling to LDView. Last step was
subfiling plus sanding the header using DATHeader.

The original L(EGO)Draw part weights 173 KB. The version I submitted to the PT
http://www.ldraw.org/cgi-bin/ptdetail.cgi?f=parts/44572.dat is (including the
subpart) 14 KB! Thx to Philo and Mike the part needs only a review by the
PT-Admins to be shipped.

w.



Message has 2 Replies:
  Re: Preparing a L(EGO)Draw part for the Parts Tracker – A review
 
Thanks, Willy, for this very informative article... I discovered many things (among them, Syncedit that looks VERY interesting - how did I miss its announcement???). (...) Here you had a favorable situation with mostly flat surfaces. Similarly I (...) (17 years ago, 4-Oct-07, to lugnet.cad.dat.parts)
  Re: Preparing a L(EGO)Draw part for the Parts Tracker – A review
 
(...) Hey! I have a user :-) Cool! Now I *must* update the web site... (17 years ago, 4-Oct-07, to lugnet.cad.dat.parts)

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