Re: triangle ordering in STL files

From: Irene Quinlan (ireneq@sanders-prototype.com)
Date: Mon Nov 23 1998 - 16:32:44 EET


Craig -

The triangles in the STL file do not have to be in any particular order,
according to the STL specification. However, the points for each
triangle must be ordered in a counter-clockwise directed as viewed from
the outside of the part. If these points are out of order they may
indeed cause problems building the part.

Let me know if you have any other questions.

Irene Quinlan
Sanders Prototype, Inc.

Craig Gotsman wrote:
>
> Greetings,
>
> A short question regarding the order of the triangles in STL files:
>
> Do the triangles have to be sorted in any specific way inside
> the STL file in order to be a legitimate input to an RP machine ?
>
> In other words, is this statement (from a colleague of mine) correct:
>
> "If the points are out of order (or not bottom-top in fact), any Stereo
> Lithography machine will construct the model improperly, if at all. As
> most of
> these types of machines work with the STL format, they build the physical
> model
> up a single layer at a time. If the layers aren't properly sorted, all
> manner
> of problems can arise."
>
> Thanks,
>
> Craig
>
> Craig
>
> 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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