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.
A CAD representation of a torus (shown as two concentric red circles) and an STL approximation of the same shape (composed of triangular planes) | |
| Filename extension |
.stl |
|---|---|
| Internet media type |
|
| Developed by | 3D Systems |
| Initial release | 1987 |
| Type of format | Stereolithography |
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.