RE: Point cloud data from rendering

From: Charles Overy (
Date: Thu Aug 23 2001 - 01:11:44 EEST

-----Original Message-----
From: Charles Overy []
Sent: Wednesday, August 22, 2001 3:23 PM
To: ''
Subject: RE: Point cloud data from rendering


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.


-----Original Message-----
From: James Carruthers []
Sent: Wednesday, August 22, 2001 2:53 PM
Subject: RE: Point cloud data from rendering

> Does anyone know if it is possible to create point cloud data from a
> rendering or renderable image. My thinking is to create a
> "virual scanner"
> add in to a render engine, create good point cloud data of a surface form
> and reverse engineer it using Geomagic, Rapidform or the like.
> It occurs to
> me that a render engine must know where the "surface" of model is and as
> rendering is more forgiving and more pervasive than solid
> modeling it would
> be of tremendous benefit to be able to generate .stl from a render type of
> application. The reverse enginnering applications have plently of utility
> for stitching holes and filling the backside of objects that have not been
> scanned and this utility could be turned to the patching of areas
> that were
> not rendered.
> Am I nuts (again!)
> Charles

Hmmmm, why not just clean up and output an STL from the "render"
application? It's certainly been done. Or "Reverse Engineer" the mesh?

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

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