The encyclopedia · Software & IT · Product decision · 1987–2010
3D Systems' STL reduced 3D shapes to triangles and became 3D printing's default file
STL, invented by 3D Systems in 1987, describes any 3D surface as triangles; its dumb simplicity made it the standard 3D-printing interchange format.
3D Systems
the move
When 3D Systems commercialized stereolithography in the late 1980s, it needed a way to get a 3D model from CAD software into its printers. The model had to be something a machine could slice into layers and trace with a laser — but the CAD formats of the day were rich, proprietary and complicated to parse.
The company's answer, developed in 1987, reduced any surface to a collection of triangles: each facet stores a perpendicular unit normal and the three coordinates of its vertices. That is the whole format — no curves, no color, no texture, no scale information — and it exists in both ASCII and compact binary forms.
The genius was the sacrifice. A triangle mesh is an approximation, so complex shapes need more triangles — but every printer, slicer and CAD tool can read and write triangles. The format lowered the cost of interoperation so far that it became the interchange standard for rapid prototyping and then for consumer 3D printing.
Because the format never needed anyone's permission or a license, it spread with the industry itself. STL has not changed much since 1987 and is now considered the standard for 3D printing, even as newer formats added color, texture and richer geometry.
why it works
- Triangles are universally parseable: any tool can compute normals and layer slices from vertex coordinates.
- By dropping color, texture and scale, the format kept every file trivially simple and unambiguous.
- No licensing or proprietary extension locked implementers out, so every vendor could support it freely.
- ASCII and binary variants meant human debugging and compact storage were both available.
what transfers
Sometimes the winning format is the dumbest one: strip the model down to what the machine must consume, and universality follows from simplicity.
what came after
STL became the de facto interchange format of 3D printing: slicers from every vendor read it, and it outlived richer rivals despite its crude approximation of curved surfaces. A proposed STL 2.0 in 2009 never displaced it, and the format remains the default export of CAD and 3D-modeling software.
references
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