Develop Slicing algorithm in client software

[Aslan0]

develop a slicing routine that takes .stl-files with orientation and layer height as arguments and returns a stack of images (svg?) that are sent to the raspberry afterwards

[Aslan0]

I started working on this but i'm very unsure about the output format. I think a folder with a stack of images (uncompressed 2 colour bitmaps maybe? what do you think?) would be better than svg because i have problems working with svg both on the input AND output side of things. :s

[entropybit]

I have read a bit how sla slicing is typically done. One of the papers should also be in seafile but I will supply a link here nonetheless: http://web.firat.edu.tr/iats/cd/subjects/Manufacturing/MTE-31.pdf

Most of the stuff I found is a bit old and talks about the adaptive slicing algorithm.
(I also read parts of this http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.15.9738&rep=rep1&type=pdf)

As far as I understand it this is an algorithm to adapt the height of the slices so that they will match the object structure, i.e., so that there are more thinner slices at regions where you need higher resolution to reliable produce the part without this "staircase effect"

However, I haven't really found any papers tackling the problem of support structures in abritrary geometries.
I only found one paper regarding the minimzation of support structures (http://www-users.cs.umn.edu/~janardan/PROP/2dlm.pdf) where this minimization is to be done on the slices.

Maybe you could supply me what you have already read ?

Btw: I originally proposed to use optimization algorithms for the slicing. I would also do the adaptive slicing, yet only if informations as minimal and maximal acceptable slice heights are known.
A simple idea to minimize the support structure could be as follows:
Assign some (virtual) mass to the structures within the single slices and simulate the downward movement by gravity. Than add support structures until there is now area left which can fall trhough the next layer ....
(This is only a crude idea but could work).

[entropybit]

Oh btw in one of the papers I also read that there is no real standard for how to store slices, so we should use whatever is most suitable to us.
Maybe I'm underestimating the amount of data but, wouldn a simple class holding the slice information be sufficient ? Instead of storing it as jpg or whatever ?

For the displaying we have to get the 3D coordinates of all points defining the STL object, the tesselation is then done to describe the surface. So we can in first order generate the slice data by building a cross section and only saving the coordinates within this cross section as a 2D array maybe for easier acessing...

[Aslan0]

The stuff you are describing is WAY more advanced than what im currently developing.

I'm developing a slicing algorithm that takes the same slice height for everything. No adaptation, nothing. And even that is really hard because im doing it by hand - at first i didnt know numpy-stl existed and now that i do, i cant install it properly. So im doing everything by hand with school-grade linear algebra at the moment. And a lot of crude techniques. And i can barely keep up because of the shitload of work i have otherwise at the moment.

And yes, i'm currently building exactly that: a class holding the slice data.

[entropybit]

What's your problem with installing numpy-stl ? sudo pip install numpy-stl should be sufficient, if your pip is not up to date try sudo pip install pip --upgrade before that

[Aslan0]

well, you tell me whats the problem.
[image: Inline-Bild 1]

2015-07-08 13:52 GMT+02:00 mithrawnuruodo notifications@github.com:

What's your problem with installing numpy-stl ? sudo pip install numpy-stl
should be sufficient, if your pip is not up to date try sudo pip install
pip --upgrade before that

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[Aslan0]

it looks like it didnt install properly or something. but i dont know how
to install it any other way

2015-07-08 13:59 GMT+02:00 Michael Hutschenreiter <
michael.hutschenreiter@googlemail.com>:

well, you tell me whats the problem.
[image: Inline-Bild 1]

2015-07-08 13:52 GMT+02:00 mithrawnuruodo notifications@github.com:

What's your problem with installing numpy-stl ? sudo pip install
numpy-stl should be sufficient, if your pip is not up to date try sudo pip
install pip --upgrade before that

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#4 (comment)
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[entropybit]

Somehow I can't see the screenshot ^^ (you did try to add an picture correct?)
It only says

[image: Inline-Bild 1]

maybe you could copy paste the output of the pip install ?
If the install fails most likely there is some missing dependency.

[Aslan0]

i tried to import the following:
from stl import mesh

and the error is:
Traceback (most recent call last):
File "/home/aslan/3D-Druck/Python Printer/sla_client/Model/slicing.py",
line 5, in
from stl import mesh
File "/usr/local/lib/python2.7/dist-packages/stl/init.py", line 2, in

import stl.ascii
ImportError: No module named ascii

2015-07-08 14:03 GMT+02:00 mithrawnuruodo notifications@github.com:

Somehow I can't see the screenshot ^^ (you did try to add an picture
correct?)
It only says

[image: Inline-Bild 1]

maybe you could copy paste the output of the pip install ?
If the install fails most likely there is some missing dependency.

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#4 (comment)
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[Aslan0]

and i installed it with apt-get and not with pip. if i tell pip to install
it now, it says its correctly installed.

2015-07-08 14:35 GMT+02:00 Michael Hutschenreiter <
michael.hutschenreiter@googlemail.com>:

i tried to import the following:
from stl import mesh

and the error is:
Traceback (most recent call last):
File "/home/aslan/3D-Druck/Python Printer/sla_client/Model/slicing.py",
line 5, in
from stl import mesh
File "/usr/local/lib/python2.7/dist-packages/stl/init.py", line 2,
in
import stl.ascii
ImportError: No module named ascii

2015-07-08 14:03 GMT+02:00 mithrawnuruodo notifications@github.com:

Somehow I can't see the screenshot ^^ (you did try to add an picture
correct?)
It only says

[image: Inline-Bild 1]

maybe you could copy paste the output of the pip install ?
If the install fails most likely there is some missing dependency.

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#4 (comment)
.

[entropybit]

This seems to be problem with your installation.
I would recommend trying to remove it (sudo apt-get purge numpy-stl ?) and afterwards install it with pip.
(also found this on stackoverflow: http://stackoverflow.com/questions/29661823/importing-of-3d-stl-image-in-python-importerror-no-module-named-ascii where comment essentially says the same)

[Aslan0]

that worked.

now the standard example throws me a different error. -.- shouldnt like the
very first example work just like that?

2015-07-08 15:31 GMT+02:00 mithrawnuruodo notifications@github.com:

I would recommend trying to remove it (sudo apt-get purge numpy-stl ?) and
afterwards install it with pip

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#4 (comment)
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[Aslan0]

anyway.... thank you.

2015-07-08 15:48 GMT+02:00 Michael Hutschenreiter <
michael.hutschenreiter@googlemail.com>:

that worked.

now the standard example throws me a different error. -.- shouldnt like
the very first example work just like that?

2015-07-08 15:31 GMT+02:00 mithrawnuruodo notifications@github.com:

I would recommend trying to remove it (sudo apt-get purge numpy-stl ?)
and afterwards install it with pip

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#4 (comment)
.

[entropybit]

Okay that's strange on my two computers it seemed to work.
I'm sure I can find the error if you post the output again. I sincerely doubt that we want to write a STL file reader completely from scratch if it would work I think / hope that this would help to go on with the displaying and slicing.
Maybe also try it with some other STL file ?
Some simple STL Files I found here http://www.eng.nus.edu.sg/LCEL/RP/u21/wwwroot/stl_library.htm
Although maybe you now more about where to get STL files than I do.
I also registered an account at some free stl library in the web where I found cool stuff like an STL File for the sword Rebellion from Devil May Cry ^^
But that's not of importance now...