From: Charles Overy <>
Date: Wed Apr 28 2004 - 02:46:21 EEST


You first question deals with the area of mesh processing and mesh geometry.
Do not limit yourself to stl as this is only one format of a mesh
description and a mesh is only one method of geometry description.

You say "The images will be developed in AutoCAD or any CAD software, then
exported as STL file. There are some huge assumptions going on there that
stl files created from various CAD programs are similar. Some CAD programs
take a strict approach to stl exprt and will only generate a mesh if the
underlying geometry is a solid. Unless AutoCad has changed recently, it
only alows export of a single solid using the stl export command. This is
pretty limiting if you are doing more artistic work where there is no
underlying reason to use a solid modeler. Also, will you engrave interior
geometry or only the surface information? How will you eliminate the
interior geometry if it exists?

 Indeed, it is not clear at all to me why you would necessarily use a mesh
if you are going to be blasting a voxel. Why not use a voxel processing
algorithm from the start. Import your geometry, voxelize it at the
resolution of your device, select the voxels to blast and then selet
coordinates of the voxels in some stepwise pattern. It will not be as fast
as some clever "nearest neighbor" type of route selection but it will be a
lot easier to program.

Just a thought

Charles Overy

  -----Original Message-----
  From: []On Behalf
Of Ahmed Issa
  Sent: Monday, April 26, 2004 10:33 PM
  Subject: [rp-ml] A QUERY ON STL FILE FORMAT

  Hi All,

  I am developing a laser marking system, which is supposed to produce 3D
images inside a cubic bulk of glass. I am sure that some of you have seen
this kind of souvenirs in the market. . I am going to develop a code to
handle the STL file and convert it into (X, Y, Z) points that resemble the
3D shape. The laser beam will be focused within the work piece at the
specific coordinates, thus allowing it to internally vaporize a spot of the
material leaving a hollow spherical spot (VOXEL in the order of micons) in a
phenomenon known as micro-fabrication or internal marking. The voxels are
not connected, however so close so that they form a 3D image. As I
understand, this process falls under Steriolithography (please correct me if
mistaken in categorizing the process).

  The problem I am facing with STL file format that it randomly sorts the
facets. I can have control over some parameters such as the resolution of
facets but some shapes are not properly tessellated (i.e. big triangles such
as the case of cubic shapes).

  My question is: does any one know good reference books or websites on this
technique, specifically on how to manipulate STL files. Also on sorting the
points in space so as to optimize the travel distance of the XYZ positioning

  Any hints or useful information will be highly appreciated, thanks.

  Ahmed Issa.

Received on Wed Apr 28 14:51:45 2004

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