Re: VRML, STL and other animals

Date: Wed Jan 10 1996 - 22:10:51 EET

Regarding the "Legal STL File" comments of Yuval Roth of Imageware:

The STL file specification is not just about file Structure, it also
about file Content. Content that is appropriate and necessary for
this application. It is the Content that makes the RP process work.

Legal STL files make it possible to guarantee that, no matter
how you slice it, you Always get Exactly Closed slice boundaries.
This makes it possible to automate the slicing process, which in
turn makes this industry possible.

Legal STL files are Not rare. Many software companies have invested
the Time, Talent, and Treasure necessary to create software capable
of valid STL output.

Unfortunately, there are also software companies who have Not made
the necessary investments, but simply dump a bunch of triangles
in a file and claim the file meets the STL specification, when in
fact it does NOT.

Perhaps we need a new format, call it SRT (Stupid Random Triangles).
Or we could use an existing rendering format like VRML. Then software
not capable of correct STL output could write to this format.
This could be added to the software documentation:
" Our SRT output requires additional processing to convert to STL
  for Rapid Prototyping use. Many of the STL fixer programs available
  can convert SRT to STL automatically. In more advanced cases, all
  you need is one of the popular Interactive Triangle Editors. You
  will need just an hour or two to select the desired SRT triangles
  and output a valid STL file."

As Manufacturing Professionals, the participants in this mailing
list know better than most the importance of meeting specifications.

If you buy software that claims STL output, you have the Right to
expect that it actually does so.
Yes, sometimes in life you are forced to eat garbage. But you should
know it is garbage you are eating. Demand better.
C. Brock Rooney, Pres., Brock Rooney & Associates Inc. (Brockware)
       268 George St. Birmingham Michigan 48009 USA
(810) 645-0236 fax/bbs (810) 645-9020 email

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