File formats
STL
Also known as: stl · .stl · archivo stl · stereolithography · estereolitografía
Short definition
STL is a file format that describes a 3D object's surface as a mesh of triangles, with no colour, no units and no printing information.
Full definition
It is the oldest and most widespread format in 3D printing, which is why almost every repository still offers it by default. It stores geometry only: a list of triangles with their vertices and normal vector. It stores no colour, no material, no units of measurement and no slicer settings. That last omission causes the classic problem of a part coming out ten times too big or too small: since the file does not say whether its numbers are millimetres or inches, each program interprets it according to its own configuration. Its simplicity is also its virtue: every program opens it, and has done for forty years.
Related terms
- 3MF3MF is a modern file format that, on top of geometry, stores colour, materials, units, object hierarchy and sometimes the slicer's full settings.
- G-codeG-code is the instruction file the printer executes line by line: where to move each axis, how much filament to extrude and what temperature to hold at each moment.
- Watertight mesh (manifold)A watertight or manifold mesh is one where every edge belongs to exactly two faces, so the solid has no holes and the slicer can tell what is inside from what is outside.
- SlicerA slicer is the program that cuts a 3D model into horizontal layers and generates the G-code with the paths, temperatures and speeds the printer will execute.
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