Infact, there is space to store colour information in an STL file.
We've succesfully used this 'STL Colour' format for some time now.
The STL file remains an ordinary STL file. The (unused until now) 2 bytes
that are included in each triangle store the colour information for each
triangle.
Of course there are some good alternatives like PLY and VRML, but especially
VRML is able to store a whole lot of other information that is not relevant
for RP systems and this increases the chances of errors during dataexchange.
Why not try to use the beauty of the simplicity of the STL file in the
colour RP world?
When colour RP is taken into a higher level, like texturemapping (as we're
currently working on), more information is needed besides the triangles, but
even in this case STL can be used (by including the texture bitmap as a
seperate file).
Jeroen van den Hout
TNO Institute of Industrial Technology
Production Development Division
Department of Industrial Prototyping
P.O.Box 5073
2600 GB Delft
The Netherlands
Tel:+31-15-2608747 / +31 6 55514510
Fax:+31-15-2608725
Visit us at:
http://www.ind.tno.nl/en/productiondevelopment/prototyping/index.html
<http://www.tno.nl/instit/indus/prototyping/index.html>
-----Oorspronkelijk bericht-----
Van: Marshall Burns [SMTP:Marshall@Ennex.com]
Verzonden: vrijdag 17 november 2000 14:01
Aan: Doty Mike; NECOINC@aol.com; List: Rapid prototyping
Onderwerp: Re: stl files
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/
For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
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