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.
