Whitespace (spaces, tabs, newlines) may be used anywhere in the file except within numbers or words. In practice, however, all facets are simple triangles. The structure of the format suggests that other possibilities exist (e.g., facets with more than one loop, or loops with more than three vertices). The file concludes with:Įndsolid name An example ASCII STL of a sphericon Where each n or v is a floating-point number in sign- mantissa- e- sign- exponent format, e.g., 2.648000e-002. The file continues with any number of triangles, each represented as follows: facet normal n i n j n k outer loop vertex v1 x v1 y v1 z vertex v2 x v2 y v2 z vertex v3 x v3 y v3 z endloop endfacet The remainder of the line is ignored and is sometimes used to store metadata (e.g., filename, author, modification date, etc).
Where name is an optional string (though if name is omitted there must still be a space after solid, for compatibility with some software). In 2009, an update to the format, dubbed STL 2.0, was proposed which evolved into the Additive manufacturing file format. Since its initial release, the format remained relatively unchanged for 22 years. The format was developed for 3D Systems' first commercial 3D printers. STL was invented by the Albert Consulting Group for 3D Systems in 1987. STL is widely used for rapid prototyping, 3D printing and computer-aided manufacturing, and supported by many other software packages.
Binary files are more common, since they are more compact. The STL format specifies both ASCII and binary representations. STL files describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. STL files contain no scale information, and the units are arbitrary. In the original specification, all STL coordinates were required to be positive numbers, but this restriction is no longer enforced and negative coordinates are commonly encountered in STL files today. Īn STL file describes a raw, unstructured triangulated surface by the unit normal and vertices (ordered by the right-hand rule ) of the triangles using a three-dimensional Cartesian coordinate system. Chuck Hull, the inventor of stereolithography and 3D Systems’ founder, reports that the file extension is an abbreviation for stereolithography. STL is a file format native to the stereolithography CAD software created by 3D Systems.
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