Re: VRML, STL and other animals

Date: Thu Jan 11 1996 - 08:42:41 EET

Yuval Roth wrote:
> However, I am extremely interested in participating in a serious discussion
> and effort to define a new format to enhance the STL format.
> The requirements of such a format (my private opinion) will be:
> 1. The file will represent only polygons (preferably only triangles - simpler
> 2. Indexed vertex representation.

Of course.
> 3. Color and Normals representation but such that it is valid and simple
> to omit (on write) or to ignore (on read).
> 4. For the color and normals: support for per vertex definition,
> or per part definition, specifically with the ability to define
> normals across creases (tangent discontinuities - at a single vertex
> more than a single normal).
> 6. ????

6. All coordinates/dimensions are in known units. Either the 'standard'
   for the file format has to specify what units are being used
   (mm, inches, angstroms, light years, ...) or the file itself has
   to include that information. The STL file format and standard
   made a very significant mistake by making the units information
   external to the file. (The STL file format states that any
   measurement units can be used, but the file format does not
   indicate what those units are.)

As for color and vertex normal information, I think that we need to be
careful that we don't make large increases in file size with very
little benefit.
  --> Mike Brindley Corvallis, Oregon, USA
"I take unanimity on any difficult topic as a danger sign."
  - P. J. Plaugher

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