Subject:
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Re: Patterns: Outline or no outline?
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Newsgroups:
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lugnet.cad.dat.parts
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Date:
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Fri, 18 Mar 2011 18:45:35 GMT
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Viewed:
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26364 times
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In lugnet.cad.dat.parts, Reuben Pearse wrote:
> Hi Lee,
>
> I've started looking at the process of creating patterns for parts. I've been
> reading through Willy Tschager article "Pattern It:
> http://www.holly-wood.it/ldraw/patternit-en.html
>
> I found a copy of Monzoom (Willy's recommended program for manipulating 2D
> shapes), but as it's in German I haven't got very far. I'm guessing there are
> some other/better programs for manipulating 2D shapes in preparation for
> converting to an LDraw file.
>
> I would be interesting to find out the tools you are using to create your
> patterned parts.
My process goes like this:
1) Find a relatively high-quality photo of the part and reorient it so it has
the right proportions and faces me head-on. (I also keep the part itself handy
for details the photo missed.)
2) Use Inkscape to trace over the image, using paths that only contain straight
lines--no curves. I use the Union/Intersection/Difference tools as little as
possible because of a bug that moves the nodes slightly out of position, which
requires me to snap them back into place. Instead I use Combine, Break Apart,
and Cut Path when I can.
3) Still in Inkscape, I break all the paths into simpler parts that I can
process. Anything with a hole in it, I break the path at two nearby nodes and
add a new segments to join the loose ends, until all my paths are composed of
shapes with no holes and no repeating vertices. (E.g., a ring shape would have
to be split into two C-shaped sections. They can be part of the same SVG path
object however.) I do put extra nodes along the edges of the pattern if the
interior details come too close to the edge, to prevent long-sliver triangles
from being made.
4) I wrote a tool in JavaScript to convert these kinds of SVG paths to LDraw
triangles; it doesn't account for winding, so when I paste its output into LDDP
I also keep LDView open (with the red backfacing BFC option on) and reverse any
shapes that came out with the wrong winding. (Every group of triangles that gets
created is either right or wrong, so fixing this in LDDP is as easy as
highlighting the right section and hitting Ctrl+W.) If my tool experiences any
problems it's usually due to the path not being right, like if it accidentally
got a curved line segment or a smooth node, which I can fix in Inkscape.
5) I run the result through DATHeader to find obvious errors and combine
triangles to quads, then check in LDDP again to be sure DATHeader didn't get too
enthusiastic and combine things it shouldn't have.
Since my last patterned parts had a couple of issues due to missing some
vertices or having some misaligned, and due to rounding errors in my JS tool,
I've been cleaning up my script and also I'll be adding Edger 2 to this process
in the future since it's very good at highlighting problems. (Next time I'll run
Edger2 before sending the part through DATHeader.) I'll post a link to the
script when it's ready.
This method isn't as quick as running an image through a program that does it
for you, but it does have the advantage of letting you get a good level of
detail out of a photo that doesn't have to be extremely high resolution. Most of
the time I'm working with photos that give me 4-5 pixels per LDU, and with the
part itself around for reference that's usually good.
In a recent part I did I also managed to cut out some quarter- and half-circle
sections so I was able to use primitives in a couple of places to reduce file
size (and improve smoothness). In that same part I also was able to break out a
subpart, because one section of the pattern was repeated on the front and back.
The subpart is about 10.4K and the main part is 59.3K so the savings were
significant; however it's the first patterned part I've been fortunate enough to
do this with.
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Message is in Reply To:
 | | Re: Patterns: Outline or no outline?
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| Hi Lee, I've started looking at the process of creating patterns for parts. I've been reading through Willy Tschager article "Pattern It: (URL) found a copy of Monzoom (Willy's recommended program for manipulating 2D shapes), but as it's in German I (...) (14 years ago, 16-Mar-11, to lugnet.cad.dat.parts)
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