You're right, Mike. Data redundancy is one of the criticisms of the StL
format that leads many people to want to replace it. But a worse problem is
that now with the advent of color fabbing (Z Corp. and TNO), StL provides no
place for the color data. There are other problems too and StL is likely to
be replaced in coming years with a better format.
Best regards,
Marshall Burns
President, Ennex Corporation
Marshall@Ennex.com
Los Angeles, USA, (310) 397-1314
http://www.Ennex.com
----- Original Message -----
From: "Doty Mike" <uq607848@hsc.hac.com>
To: <NECOINC@aol.com>; <rp-ml@bart.lpt.fi>; <Marshall@ennex.com>
Sent: Thursday, November 16, 2000 22:27
Subject: Re: stl files
>> Can any one tell me how to look into an STL file and see what information
>> is contained.
> John,
> You can find this information at http://www.ennex.com/fabbers/StL.sht.
> Marshall Burns
Very interesting write-up on stl format. I don't understand why the
normal needs 3 coordinates, since it is only used to indicate which side of
the face is inside the enclosed volume of the solid and which side is
outside. It seems that the shape could be almost as accurately stored in a
file 1/3 the size by using the normal coordinates as a fourth point to
describe the vertex of a tetrahedron, projected along a normal vector at the
center of the other three points. the direction of the surface normal needs
only a single sign bit. the magnitude of the normal would be 0 if the face
lies on a plane, otherwise it would lie on the curvature of the surface of
the shape. Which side of the tetrahedral surface is interior to the solid
and which side is outside is determined by the sign bit according to the
right-hand rule applied to the three points.
Mike Doty
For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
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