Re: point cloud data into surface data

From: Peter H. Gien (
Date: Thu Jan 25 1996 - 04:19:31 EET

Suzanne Fox Buchele mentioned that importing Surfacer data into Pro/E is a
problem since the model cannot be manipulated ( as a true solid.)

This is part of a larger problem: How do you convert a surface model into a
valid solid. Some solid modeling packages allow you to do this provided that all
your surfaces can be stitched together to form a valid solid. Other packages
are much dumber and simply display the surfaces.

 It is helpful to remember that the best solid model is one that has been
designed by an expert in that particular CAD package. Translating it to another
CAD system discards much valuable design information. All is not lost however,
provided you are moving from one ACIS based package to the next. ACIS to
Parasolid ??? Pro/E to ACIS??? Tough sledding I'm afraid.

Getting back to Suzanne's question, it is helpful to ask what she means by a
"CAD" system. For example,

Import an STL file into Caligari TrueSpace and you can manipulate it very well.
You can even Boolean Union it to other objects, smooth the mesh and other great
stuff. Why is this possible here and not in Pro/E? Because TrueSpace is a
Polyhedral modelor. Brute force, but it works well with models that are
inherently triangle based (or point cloud data that has been tesselated if you

On the other hand, Nurbs based surface modelors such as Surfacer are great for
producing Nurb surfaces that can be passed as compact mathematical surfaces into
Pro/E, Alias and LightWave via the IGES format. In neither case will an editable
solid model result. By editable, of course, I mean manipulating the state tree
of the solid model, and not simply scaling and moving.

Peter Gien
POGO International, Inc.

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