Adrian Bowyer wrote:
> This was a problem with a known simple solution when the STL format
> was defined. As that solution had been around since the time of
> Poincaré (1854 - 1912), if not Euler (1707 - 1783), that is a bit
> annoying. It's the sort of thing that happens when you let mechanical
> engineers (like me) define a data structure...
Are you sure that the problem with STL aren't due to incomplete
specifications? The 3D Lightyear help file (interestingly enough
labeled 1.2.1 even in the 1.5.1 release) has a section in "STL Format"
with the following rules:
1. All triangles much conform to the right hand rule
2. All exterior surfaces must be devoid of gaps
3. Each triangle must share two of its vertices with each adjacent triangle
I presume these rules are in the spec by 3D Systems. You can't easily
derive all of these rules from the reverse engineering of the file.
Steve touched on something in his first post that made me think that it
would be nice to be able to test if STL files conformed to what 3D
Systems intended. (Think "syntax checker.") I repair some of the
customer files that come through our operations, and Magics, 3D
Lightyear, and SolidView all disagree about what a "good" file is...
Which is disconcerting, to say the least.
-- Todd Pederzani tpederzani@protocam.com ProtoCAM System Administrator 3848 Cherryville Road Phone: (610) 261-9010 Northampton, PA 18067 Fax: (610) 261-9350Received on Wed Dec 06 17:14:36 2006
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