STL (file Format) - ASCII STL

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 n_i n_j n_k outer loop vertex v1_x v1_y v1_z vertex v2_x v2_y v2_z vertex v3_x v3_y v3_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". 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) but in practice, 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.