Re: Sculpting digital dinosaurs

[Syndesis Corporation <syndesis@inc.net>]

At Fri, 24 May 1996 11:16:01 -0400, muriel29@wavenet.com (MC2) wrote:
>
>        The new (May 18 [Vol. 149]) issue of _Science News_ has an
>article on 3-D scanning technology that is used, for example, to scan
>military pilot's bodies for the manufacture of form-fitting flight
>suits and helmets ("Fit for a King," pp.316/7).
.
>        I assume the digital bone replicas are milled; the article
>doesn't say.  But I've often wondered if stereo lithography could be
>used for this purpose.  (Indeed, the article mentions SL being used to
>manufacture a 6" Buddha statue.)  Does anybody know what the state of
>the technology of SL is?  What kind of tolerances are achievable?  How
>expensive is it?

Ah, finally a topic I can rant about with some authority!  

There are several technologies available for making real-world models
from computer data.  Stereolithography (STL) proper comes from 3D
Systems, http://www.3d.com .  They sell ~$30K devices that can make
models up to about 12-18 inches in dimension.  There are many service
bureaus around the country that can create objects for you in this
way.  I have a triceratops model about 4 inches stem-to-stern made
with this process.  The service bureau said this would cost about
$400.  They charge on a sliding scale depending on how much polymer
and laser time your model consumes.

3D Systems' device uses a vat of liquid polymer that hardens with
exposure to laser light.  The bottom of the vat is a platform, full of
holes, that raises to the level of the liquid.  A laser scans the
surface much like the way the electron beam scans a TV image,
hardening each "wall" of the object as it goes along.  The platform
lowers by a small fraction of an inch, the polymer flows over the
surface of the last hardened layer, and the process begins again.  The
resolution is variable.  The laser beam can focus as tightly as
1/10,000 of an inch.

Other techniques can create 3D models from 3D data.  There are many
companies offering milling machines of various kinds.  In particular,
I can think of some that mill styrofoam with reasonable precision.  I
believe Roland (yes, the music synthesizer people) makes a low-cost
milling machine for PCs.  Imagine being able to purchase a full-size
model dino skeleton for just a few hundred dollars.

STL machines are very popular in the engineering field for rapid
prototyping of CAD models.  STL is also an inexpensive alternative for
movie-makers who need quick props like phasers, tricorders, etc.

As in the Science News article, STL is often combined with laser
scanning of the a real-world object, using scanners such as those from
Cyberware at http://www.cyberware.com .

With the emergence of the Web standard for 3D objects, called VRML,
and the addition of 3D viewers to browsers such as NetScape, and the
appearance of low-cost video cards that accelerate 3D operations, it
won't be long before you'll be spinning 3D fossil images on your
personal computer.  In fact, you can do it now at
http://www.notam.uio.no/~oyvindha/ribs.html and
http://dev.uol.com/~prem/fossil.html .

My company makes InterChange, a 3D file format translation package
that exchanges polygonal data between more than 40 file formats,
including stereolithography format, and soon the Cyberware format.  My
company's software was used to convert the 3D computer models used for
special effects on television shows such as seaQuest and Star Trek
Voyager to the plastic models used in Revel kits as well as the
computer games for those shows.

- John Foust

Syndesis Corporation
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