On 2021-03-31 16:12, NateTG wrote:

I agree. I have done it in C++ and would not try to use any scripting
language to do it.

Carsten Arnholm

cacb wrote

Why I'm doing this with scripting tools is because I'm not experienced
enough to code 3d in C++ (I'm a 51 years old craftsman not a CS specialist
nor professional), but I'm working on this since 2015 in order to have
something like Pepakura, and it works well, I managed to have the automatic
version unwrap a 2000 triangles model (took hours) that I successfully built
on cardboard (took 2 weeks). My primary goal is to unwrap furniture clothe
so I won't need more than 2000 triangles most of times. The fact is that
automatic unwrapping is very slow with javaScript, for the moment I'm using
a strategy that works nicely : I paint my volume so that it has groups of
faces that I unwrap separately, it considerably improves the speed, but I'm
now hoping that OpenSCAD could help me more. At first I wanted to use
TensorFlow but I didn't understand how it works.

I'm already impressed by the speed, the sensation of power that OpenSCAD
gives. I will try to understand the code that NateTG gave me, it is so much
simple than what I did, but I'm afraid that I need to take little steps not
to lose tack of what I'm doing.

I managed to have the faces neighbors using search(), now I need to start
basic unwrapping without checking for overlap. On the OpenJSCAD version,
what I did to check overlap was very foolish, I built a 2g geometry with all
faces already unwrapped and check if this geometry and the current one
intersects, takes very long but works. On vanilla JavaScript I tried lots of
things but none worked, so this version is only semi-automatic. Yesterday I
used it to unwrap the hand model that I'm using here.
http://forum.openscad.org/file/t3103/Capture_d%E2%80%99%C3%A9cran_de_2021-03-31_17-10-41.png

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Ronaldo wrote

Thank you, I remember I read that thread several times while I was looking
for a way to optimize my script. To unfold the concerned  shape, I saved it
to STL, then opened it in Wings3d, select the 4 surfaces separately and
colored their faces in order to have them group, then export it to OBJ where
the data (vertices, faces, groups) can be easily read. It took about 2
minutes to unfold them all with a vanilla js script. So I hope it will be at
least 2 times faster with OpenSCAD. Sadly, what I've read from now makes me
think that it won't be possible (or at best it will be hard) to write an
automatic version as I didn't find a way to have an OpenSCAD script make
conditional actions based on an intersection result (I only need to check if
the intersection return something), but for the moment I will try to write
the rotation of a neighbor triangle.
http://forum.openscad.org/file/t3103/Capture_d%E2%80%99%C3%A9cran_de_2021-04-01_09-24-05.png

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function unit(v) = v/norm(v);

module connect(a,b,c,d) {
translate(c)
mirror(unit(a-b)+unit(c-d))
mirror(a-b)
translate(-a)
children();
}

t1 = [ [3,2], [13,6], [1,12] ];
t2 = [ [-3,2], [-13,6], [-1,5] ];

color("gray") {
polygon(t1);
polygon(t2);
}

color("magenta")
connect(t2[1],t2[2],t1[1],t1[2]) polygon(t2);

color("blue")
connect(t2[0],t2[1],t1[0],t1[1]) polygon(t2);

Ronaldo wrote

Thank you again, I will look at your code that seems interesting, I failed
to use mirror to attach neighbors on OpenJSCAD. I managed to have my first
neighbor rotation done using the logic I developed on my other versions. And
now I'm kind of stuck as I must update data of that neighbor that I rotated
and it's something that I'm not sure is possible within OpenSCAD logic. It I
can update those points I will only need to keep on doing the same with
other neighbors, otherwise for each new neighbor I will need to do
everything again ?
http://forum.openscad.org/file/t3103/Capture_d%E2%80%99%C3%A9cran_de_2021-04-01_14-57-51.png

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gilboonet wrote

OpenSCAD tends to be pretty slow.  In general, I would expect JavaScript to
do the same things more quickly.  So if "unfold" is taking to too long in
JS, it might be useful to check whether you're doing the "unfold" in a
particularly inefficient way.

One of the biggest frustrations that I have with OpenSCAD is that there's no
good for user code to take advantage of the geometry engine.

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NateTG wrote

The way I currently unfold is simplistic, I start from a face, then if you
click on "auto" button it unfold closest neighbor and keep on till there's
nothing to do, it is  here
https://github.com/gilboonet/gilboonet.github.io/tree/master/depl_edit  .
I planned to make something more complex but I didn't manage to have a solid
overlap detection function, so I didn't go further. What do you mean by an
inefficient way ? Is there a way to weight an unfold path efficiency ? (a
tree to climb up and down till every faces are unfold ?) I hope that
OpenSCAD could be helpful to develop such technique.

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