Re: [rp-ml] algorithm&implementation for STL slicing

From: Sebastien Bailard <>
Date: Fri Aug 25 2006 - 06:26:02 EEST

On Thursday 17 August 2006 19:01, you wrote:
> At 4:25 PM -0400 8/17/06, Sebastien Bailard wrote:
> >For raw 3D structured light scan to stl , there is some open source
> > software called . (This is the opposite of what
> > you are asking for, as far as I can tell.) It is GPL'ed python code.
> Hi Sebastien,
> Thanks for all the info! Splinescan looks interesting and fun - I may have
> to give that a try.
Do. If you need support, you'll have to get it through the splinescan mailing
list. The lead developer's working on development, not documentation just
now, but someone should answer. I have no idea when they're going to publish
their next release.

They've got some interesting tweaks in the pipeline - they're going to publish
a hardware package that you can RP, so all you have to do is assemble it,
bolt on a camera, laser pointer diode, cylindrical lens (glass rod), and
you've got the scanning unit. For the turntable, just go scrounge a
turntable and have your laser printer print out a paper encoding strip*,
paste it on, and you're good to go. The camera/python code figures out where
the turntable is by looking for the encoder strip.

I've been daydreaming that all you need is a sheet of paper printed with
artoolkit tags and a camera, and you could put an object on the sheet, take
loads of photos, and then dump them into gpl'ed code that figures out all the
computational geometry and spits out your point cloud/simplical surface/.stl
file. It would take some keen programming and computational geometry, but it
would be so useful.

If you happen to be interested in the computational geometry background for
all this, look at "Surface Reconstruction from Unorganized Points" by
H. Hoppe 903 citations, and fairly readable,

> >Roy - what materials are you working in? You may be able to use our
> > extrusion head along with the control software:
> >
> >nHead
> I've been aware of Reprap but didn't realize or look closely at the
> software part of the project. have to take a closer look. My materials?
> Well... this is a 'for art' project so I have been looking at various
> materials which flow and then harden - slurries of clay, etc. I was
> thinking about wax but wanted to avoid the complexity of a heating element.

I would go with kaolin slurry or store bought "earth clay" slurry or slip as
well in that case, or cncmill/RP a reprap extruder head and use
thermoplastic. It'd be a lot easier to set up.

Waxes can be nasty - one tuft of cat hair in your feedstock, it clogs, and
unless you've got a thermostat or thermal-overload detector and hard shutdown
circuit, it all goes up like a candle and you kiss your studio goodbye. So
many artists die just because they forgot to use a double boiler, crockpot,
or soup warmer to heat their wax, so they just put it directly in a pot on
the heating element, maybe go and answer the phone, the bottom layer
liquefies and starts to boil even though when the top's solid, then you get a
big cloud of vaporized wax and poof! Wax is the main reason art foundries
and studios burn down, so you'd want to trouble shoot the hell out of any
autonomous 24/7 mechanism you're building that uses wax. A slurry printer
screws up, and all you've got to clean up is a puddle.

One thing to realize is whatever earth clay you go with is possibly going lose
all its plasticity if you run it through a feed system - it depends how happy
the bacterial colony is in the clay, after it's been extruded. (Bacteria
makes the gel that lets the clay platelets slip past each other.) But a
couple spritzes with dilute vinegar could perk it up again/
If you're not going to work the clay after extruding it, this doesn't matter.

You might be able to use a good oilclay (aka plasticine, modeling clay)
instead of wax. Oilclays liquefy when heated, but I don't think they can
One problem with oilclay is you can't sell it as a finished piece without
going through the casting/moldmaking steps. Wax or thermoplastic you can do
lost wax casting with, slurries you can fire in a kiln.

> For a 'print head' I have been tinkering with building a peristaltic pump -
> the idea being that with that I can deposit a measured amount of material
> that is fairly viscous and it seemed a simple way to do it. It's all in the
> testing/failing stages now.
Sounds fun. Did you see

Think you can clip one onto your 'Drip Painter' machine?

Apropos of nothing, we're using wood filler for a test material. It's pretty
much wood glue (polyvinylacetate) and marble dust.

> I'm assuming (and hoping) that this will be a functional "expressive" 3
> printer - along the lines of Giacometti type forms. I think I can get a
> fair degree of precision in placing the material- and the material will
> slump and distort in unpredictable ways. The art/sculpture "part" of this
> is both the machine as it's working and the forms it creates.
> --Roy

It's an interesting approach. Sort of like manipulating the hell out of the
negative in the darkroom, where I'm stuck on photorealism/toolmaking - I want
to image an oilclay model or broken machine part, work up the virtual image,
print it, and have a perfect duplicate.

How are you planning on creating your input code - c code that bit bangs the
printer port and the motors do their thing, traditional cad cam -> g code ->
emc (linux machining controller - ), or something esoteric
whipped up in processing? (algorithmic art / data analysis tool with thriving
community - ,


-Sebastien Bailard
Received on Fri Aug 25 05:38:39 2006

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