Re: Attn. Pro/Engineer users!! Attn. Pro/Engineer users!!

From: Anthony Martin (
Date: Fri Dec 01 1995 - 09:20:51 EET

On Thu, 30 Nov 1995, BROCK ROONEY wrote:
> On STL generation:

... 6 good advantages of STL files deleted

> STL format follows the KISS dictum of good engineering design.
> Any beginning computer programmer can create a program to read binary
> stl files in less than 20 lines of code. Alternative CAD standards
> (perhaps STEP) are much more complex.

This one might be the most important of all. With this simplicity comes
universal support and portability. As far as I know, all true 3-D CAD
systems can produce an STL file. You can be guaranteed that if you send
an STL file to an RP house, they can handle it no matter what system
created it. But try sending a Pro/E or IDEAS model to an RP house.
Unless they happen to have the same system that was used to create the
file, they won't be able to use it.

Even an IGES file differs greatly depending on how it was produced. An
IGES file can contain so many different data structures, the quality of
the model depends very much on the implementation. However, an STL file
has ONE data structure, the facet (triangle).

(Actually the key behind the STL format is the triangulated mesh. The
particular STL standard is somewhat lame, e.g. why include the normals?,
but there are several similar formats for representing a triangulated mesh
and most share the same advantages.)

The only disadvantage of the STL file that I see is the inability to
exactly represent curved surfaces. However, well-written software can
easily process files with >200,000 facets in a reasonable amount of time,
and with that many facets, almost any part can be represented with
significantly greater accuracy than any RP system is capable of.

I suspect that the STL format has a long life ahead of it, and I don't
see anything replacing it any time soon.


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