Re: STL viewer for irix

From: Justin R. Kidder (
Date: Tue May 20 1997 - 00:01:22 EEST

On Mon, 19 May 1997, Elaine Persall wrote:

> Justin wrote....
> >don't have my own graphics engine yet, I wrote a function to output STL
> >(ascii) so I can view it using another program. We're still fine
> >tuning..............
> This makes me cringe since our first attempt to use CT or MRI data (1990)
> was written in such code. Any attempt to slice or view was painful at best
> with hours wasted. Small segments of data resulted in massive file
> we wrote our code to produce .SLI files with an automated
> support already in place. Files could be ready in less than 30 minutes and
> built in less than 12hours. STL out could be produced for other
> applications such as just viewing or input back into CAD.
> ELaine

Actually, we took a somewhat different approach to the segmentation than
the traditional "slice-by-slice and reconstruct" approach. By using a
volumetric technique based on the idea of "deformable models" (there have
actually been many such techniques proposed, such as active cubes, active
blobs, etc), we end up with a triangularly tessellated model of the
segmented object. The advantage of this technique is that it is highly
automated, very fast (under a minute on an Indigo2 R4400 for most of the
datasets we've tested) and ready for rendering. The algorithm we're using
also makes an attempt at balancing the number of triangles needed for the
surface against surface accuracy, so small data sets won't result in
tremendous file sizes. Slicing would still have to be done to obtain .sli
files, of course, but I think that most commercial software still has to
do this anyway. The STL output is just for viewing at this point.

Justin Kidder, Research Asst. | Automation and Robotics Laboratory | University of Pittsburgh
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