ATTN: Bert VandenBerg RE: stl file comparison

From: Monica & Glenn Whiteside (
Date: Wed Jun 17 1998 - 07:43:31 EEST


The problem with polygonization of a scanned point cloud is that any
outliers (stray points) can severely distort the STL model. Does Hymarc -
Hyscan software filter out these outliers when scanning? You can spend the
time to clean these point(s) up, but this can be time consuming. Why not
let the software automatically do the work?
Imageware's Surfacer allows you to set a "max. checking distance"
(as noted in an earlier e-mail 6/14 by K.T. Durai) say .100 in., which will
eliminate these outliers. Does Hymarc - Hyscan have a similar control to
use when creating STL's? Say a certain control distance from the point
cloud? This might be handy but I'm not sure how well this would work for
certain geometries and would depend on the point scan density.

You said that the points defining the polygonization are
associated/projected to design surfaces only if they are close enough.
This sounds like an extra step - converting scanned point data to STL then
best fitting to design surfaces? Why not just check the point cloud
directly to the design surfaces? You can eliminate the outlier points by
setting the "max checking distance" and set weights relative to certain
surfaces so that the points will only be associated to the closest surfaces
(or curves or other point clouds). One advantage of the software we have is
that we are able to work with multiple sets of points in one model (very
handy when checking tooling assemblies involving multple surfaces),
something that I don't believe Imageware can do at this time.


Glenn Whiteside
Cessna Aircraft Co.

For more information about the rp-ml, see

This archive was generated by hypermail 2.1.2 : Tue Jun 05 2001 - 22:45:58 EEST