Re: stl files

From: Marcus Joppe (mjoppe@marcam.de)
Date: Fri Nov 17 2000 - 19:29:12 EET


Marshall,

an extension for the STL format to use colour information has already been
published to the rp-ml from Aad van der Geest one year ago.
We are using this extension within our new RP software VisCAM RP which will be
shown on the Euromold 2000 in Frankfurt and released in the first quarter of
next year. I'm not sure, but I think other software vendors are using the colour
extension in the same way.

Following is the extension of the STL format from Aad van der Geest:

For every triangle the colour information is in the attribute count (16 bits).
bit 15 always 1 (to distinguish from normal stl files)
bit 10 to 14 intensity level for red (0 to 31)
bit 5 to 9 intensity level for green (0 to 31)
bit 0 to 4 intensity level for blue (0 to 31)
In this way there are 32768 different colours.

--
Best regards
Marcus Joppe

----------------------------------------------------- Marcam Engineering BIBA Gebaeude Marcus Joppe Hochschulring 20 28359 Bremen Tel.: +49 (0)421/218-5633 Fax: +49 (0)421/218-5633 eMail: mjoppe@marcam.de Mobil: +49 (0)170/751-8801 -----------------------------------------------------

Marshall Burns schrieb:

> Jeroen, > > I also received a similar e-mail from Materialise, whose Magics 6 does > something similar to what you are describing. > > Yes, there is *room* in an StL file for color or other information, but > your inclusion of that information creates a new data format. In my message > yesterday, perhaps instead of saying that there is "no place" for color, I > should have said that there is no definition of color in the StL spec. > > StL is a technical specification for a data format > (http://www.ennex.com/fabbers/StL.sht). If you include color or other > information in the file, you are creating an extension or modification of > the StL spec. If you publish the format that you use for this information > (or if enough other people reverse engineer it and adopt it), then it may > become a new standard. If you only use vacant data elements from the > original StL spec, then your new format should be downward compatible with > programs expecting plain StL files. > > If TNO and Materialise do not intend to keep your StL extensions > proprietary, perhaps you'd like to post their definitions to the RP-ML. If > the way you represent color is different, then we're in for a little format > war. > > Best regards, > Marshall Burns > President, Ennex Corporation > > Marshall@Ennex.com > Los Angeles, USA, (310) 397-1314 > http://www.Ennex.com > > ----- Original Message ----- > From: <J.vandenHout@ind.tno.nl> > To: <Marshall@ennex.com>; <rp-ml@bart.lpt.fi> > Sent: Friday, November 17, 2000 06:50 > Subject: RE: stl files > > > 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 > > > > 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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