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STL (STereoLithography) is a file format native to the stereolithography CAD software created by 3D Systems. STL has several after-the-fact backronyms such as "Standard Triangle Language" and "Standard Tessellation Language".〔. Many names are used for the format: for example, "standard triangle language", "stereolithography language", and "stereolithography tesselation language". Page 55 states, "Chuck Hull, the inventor of stereolithography and 3D Systems' founder, reports that the file extension is for stereolithography."〕 This file format is supported by many other software packages; it is widely used for rapid prototyping, 3D printing and computer-aided manufacturing.〔 Chapter 6, Rapid Prototyping Formats. Page 237, "The STL (STeroLithography) file, as the de facto standard, has been used in many, if not all, rapid prototyping systems." Section 6.2 STL File Problems. Section 6.4 STL File Repair.〕 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. 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. STL coordinates must be positive numbers, there is no scale information, and the units are arbitrary.〔Fabbers.com, The StL Format: Standard Data Format for Fabbers, reprinted from Marshall Burns, Automated Fabrication, http://www.ennex.com/~fabbers/StL.asp stating, "The object represented must be located in the all-positive octant. In other words, all vertex coordinates must be positive-definite (nonnegative and nonzero) numbers. The StL file does not contain any scale information; the coordinates are in arbitrary units."〕 == ASCII STL == An ASCII STL file begins with the line solid ''name'' where ''name'' is an optional string (though if ''name'' is omitted there must still be a space after solid). The file continues with any number of triangles, each represented as follows: facet normal ''ni nj nk'' outer loop vertex ''v''1''x'' ''v''1''y'' ''v''1''z'' vertex ''v''2''x'' ''v''2''y'' ''v''2''z'' vertex ''v''3''x'' ''v''3''y'' ''v''3''z'' endloop endfacet where each ''n'' or ''v'' is a floating-point number in sign-mantissa-"e"-sign-exponent format, e.g., "2.648000e-002" (noting that each ''v'' must be non-negative). The file concludes with endsolid ''name'' 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). In practice, however, all facets are simple triangles. White space (spaces, tabs, newlines) may be used anywhere in the file except within numbers or words. The spaces between "facet" and "normal" and between "outer" and "loop" are required.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「STL (file format)」の詳細全文を読む スポンサード リンク
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