Re: Selling RP, color questions

From: Stephen J. Rock (
Date: Tue May 05 1998 - 17:51:32 EEST

Nkin wrote:
> ... First priority should
> probably be a general strategy which would allow any such system to deal
> efficiently with both shape and color ...

As an extension to defining color, how about material composition &
which may vary discretely or continuously throughout a part?

Does anyone care to suggest potential applications? (Some have already
demonstrated using processes like MD*.)

> The STL format was apparently designed to allow for a facet attribute such as
> you describe. This would seem the logical approach for relatively simple
> coloration - in which different models or even different facets of models are
> built in appropriate colors. It would not, however, allow for complex
> variation within facets.

Consider "Texture Mapping" as applied in the Computer Graphics
community. If
the only concern is surface color, it should be possible to associate a
color defininion to each planar facet.

> ... Accepting the
> STL dominance as a demonstration of its power...

STL is actually quite a powerless representation. It represents parts
using a
collection of oriented facets sitting in space without providing any
topological relationships between them or any way to define higher-order
geometric primitives. If a facet is "lost" during translation, it is
not at
all obvious from examining the file, and the format is exceptionally
with vertex coordinates repeated numerous times. Its dominance is much
likely due to being first to market and the simplicity with which it can

It will serve the RP community well if an improved alternative to STL
can be
developed & accepted before integrating color/properties into part


Stephen J. Rock
Center for Automation Technologies
Rensselaer Polytechnic Institute
Troy, NY 12180  USA
(518)276-8652  Fax -4897

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