STL (file format)
STL (file format)
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STL (file format)

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STL (file format)

STL is a file format native to the stereolithography CAD software created by 3D Systems. Chuck Hull, the inventor of stereolithography and 3D Systems’ founder, reports that the file extension is an abbreviation for stereolithography, although it is also referred to as standard triangle language or standard tessellation language.

An 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. 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. STL files contain no scale information, and the units are arbitrary. STL files describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. The STL format specifies both ASCII and binary representations. Binary files are more common, since they are more compact.

STL is widely used for rapid prototyping, 3D printing and computer-aided manufacturing, and supported by many other software packages.[citation needed]

STL was invented by the Albert Consulting Group for 3D Systems in 1987. The format was developed for 3D Systems' first commercial 3D printers. Since its initial release, the format remained relatively unchanged for 22 years.

In 2009, an update to the format dubbed STL 2.0 was proposed, which evolved into the Additive manufacturing file format.

An ASCII STL file begins with the line:

where name is an optional string (though if name is omitted there must still be a space after solid, for compatibility with some software). The remainder of the line is ignored and is sometimes used to store metadata (e.g., filename, author, modification date, etc). The file continues with any number of triangles, each represented as follows:

where each n or v is a floating-point number in sign-mantissa-e-sign-exponent format, e.g., 2.648000e-002. The file concludes with:

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