STL file format

From: Gill Barequet (Tel Aviv  University)
To: RP-ML
Date: Friday, September 16, 1994
Subject: STL file format
     As far as I know, 3DS do not consider the STL file format (ascii and binary)
as proprietary information, but encouraging everyone to use it (instead of
file formats of other vendors!) and push it towards being a standard. (They,
however, do not reveal their machine-ready code---SLI, if I recall correctly.)
     3DS have publicized their format long ago in:
\bibitem[3DS]{3DS}
{\sc 3D Systems, Inc.},
{\it Stereolithography Interface Specification},
July 1988.
     For whoever interested, the binary STL file format is very simple:
80 bytes for free comment (ascii text);
4 bytes for number of triangles (long integer);
Then come <#-of-triangles> records, 50 bytes each, where each
such record consists of:
(a) 12 bytes for the normal vector (X, Y, and Z components, 4 bytes each,
    in a standard ANSI floating-points format);
(b) 12 bytes for the first vertex (X, Y, and Z, 4 bytes each, same format);
(c) 12 bytes for the 2nd vertex (same format);
(d) 12 bytes for the 3rd vertex (same format);
(e) 2 bytes (word) for byte count (usually not in use, thus simply containing
    hex 0000).

Gill.