RE: Point cloud data from rendering

From: James Carruthers (
Date: Thu Aug 23 2001 - 05:15:24 EEST

> JIm,
> Thanks for your note. I would be happy to send you a file to
> illustrate why
> it is not practical or in many case feasible to "clean up and
> output an STL"
> from the original application. Consider 10,000 objects, Many of them
> interior or partially interior to the building. Just attempting to union
> these objects (assuming there are no errors) brings the mightiest
> workstation to its knees. Plus once it is unioned, say you want to make a
> change to one of the parts, you have lost the original data and
> most of the
> utility of RP.
> Can you help me out a bit more with what you mean by ""Reverse
> Engineer" the
> mesh?" I have tried using Rhino for instance to create a solid from a
> suface mesh and actually the Rhino site steers one towards
> applications like
> Geomagic and Rapid Form. The problem with these programs is that
> they fall
> down when the data points are not fairly regular. For example a
> large face
> on a dxf mesh has only four points, one on each corner. The
> algortihms used
> to surface the data in Geomagic and RapidForm don't like this and dont see
> that as a surface. If one pulls in the face data then you are back to stl
> patching just like in programs like MagicsRP. My thinking then is to
> generate regular suface data from a virtual object.
> Our end result right now is that we do use Rhino and FormZ to redraw the
> structures but this, for obvious reasons, is suboptimal.
> Looking forward to hearing your thoughts.
> Charles

Ah, I didn't catch your second message. You need some sort of "shrinkwrap"
functionality. I don't think a "virtual scanner" is really going to help, at
least not coming at it from the direction of the rendering engine, they're
very "dumb" and rely on tricks and fakery, they have very little idea what
they're doing.

James Carruthers
Hydraulic Design
--3D Modeling and Design
--Rhinoceros 3D Sales and Training

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