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 CAD / LDraw Files / Parts / 6569
6568  |  6570
Subject: 
Re: Advice on hair pieces
Newsgroups: 
lugnet.cad.dat.parts
Date: 
Tue, 21 Sep 2010 15:26:25 GMT
Viewed: 
20075 times
  
The quad adjustment for this piece showed that out of five quads out of
alignment, it was able to fix four of them within the bounds of round-off error
(that is, it didn't deviate the vertices from outside of what they could have
been before stl2dat rounded them off). The fifth one it was not able to
reconcile under any circumstances, so I made the tool split those cases along
the edge where the angle between the two triangles would be smallest.

It would be interesting to have a configurable threshold, a 0.1ldu move is not
visible and might bring more quads to flat state.

That's a relief. Anathema has made other quality headgear parts so if he's doing
manual adjustments then I feel comfortable doing the same. Just as a heads-up by
the way, your last comment there deleted your certify vote.
Thanks - fortunately it was certified by two other peoples ;o)

On a related subject if this particular part goes well for me I'd like to do
similar cleanup on 30475. When Mdublade submitted it he apparently only turned
the hair into the correct orientation, but no primitive substitution was done on
the interior and while the quads are all coplanar within 3°, they were obviously
never cleaned up further to a tighter 1° spec. I didn't check out whether the
interior is too small for the head, but I'd bet that's the case.
Probably...

Since I have
that part I'm positive I can fix the interior. I assume the usual etiquette
there is to contact the person first where possible. I know that resubmitting
just to improve coplanar tolerance when it's "good enough" is frowned upon, but
it'd be worth cleaning up the other issues.
There is a special policy for LUT parts: "Once the part has been submitted to
the Parts Tracker, any reviewer finding errors may fix them immediately and
re-submit the fix without asking permission, since the original author is the
LEGO Universe Team." (see http://www.ldraw.org/Article490.html)

I can't tell you how many times I've wished I had your scanner, but I have no
head for mechanics. Some parts just haven't been released to us yet, like the
still-mysterious x79.
The good point is that DAVID laser scanner (http://www.david-laserscanner.com/)
doesn't even require mechanics, and the free version is truly usable. I made my
first scan (Fabuland bear head) with it and a hand-held cheap line laser. That
said, it works better with some mechanical sweep (but a simple mechanical
kitchen timer is reported to work well!) and the paid version (better
resolution, easier assembly)

And BTW x79 is actually part 4505... It would be a good target for a laser scan
(but I don't have it!)

I'm not sure there's a very ideal solution for joining scanned sections to
primitives except for looking for a certain vertex tolerance and making
adjustments where possible.
That was the general idea I had. Make vertices of the mesh snap either onto
closest vertices, edges or surfaces with different adjustable thresholds.
In the case of part 44358, when I joined the
interior to the cylindrical indentation in the middle, I actually added 4
triangles because I needed to go from 12 points to 16. If not for the problem of
12-point circles I think some kind of limited primitive detection and automatic
substitution would be feasible. As it is I think detecting places where a simple
set of primitives could go is quite doable as long as there are hard lines
around the points in question.
Yep... adapting 12 to 16 would not work with the above method. :(
Philo



Message has 1 Reply:
  Re: Advice on hair pieces
 
(...) Ah, I was not. Very interesting. I'm still plowing ahead with upgrading Edger regardless because I'd like that built into this tool, but options like making inlining parts optional and not adding conditional lines within a certain angle (...) (14 years ago, 21-Sep-10, to lugnet.cad.dat.parts)

Message is in Reply To:
  Re: Advice on hair pieces
 
(...) Well, at least splitting into triangles at the middle would produce a fairly clean result in that it would eliminate artifacts, but at the cost of creating extra triangles. I've been working on my adjustment tool and my initial results have (...) (14 years ago, 21-Sep-10, to lugnet.cad.dat.parts)

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