Design Nomenclature / Form & Geometry
Sweep
Also called revolve, lathe, rail sweep, surface of revolution
Moving a profile along a path curve, generating surface as it goes, with the profile's orientation set by a rule — held fixed, kept normal to the path, or governed by a second rail. A revolve is the special case where the path is a circle about an axis; an extrude is the case where it is a straight line.
In practice
'Sweep 1 rail' and 'sweep 2 rails' differ in whether the profile may also scale as it travels. Call the rotational case a revolve or a lathe — it is worth naming, because it is the one the shop can actually turn.
Not to be confused with
- LoftBuilding a surface through a series of profile curves placed along a form — the skin passes through each section rather than dragging one along a rail. Section count, section ordering, and matched start points govern the result; mismatched point counts or reversed curve directions produce the classic twist. With two sections it degenerates to a ruled surface.
- ExtrudeSweeping a profile along a straight path, generating surface behind it. A closed profile extruded gives a prism — the operation that makes a cube from a square and an I-beam from its cross-section. In a mesh, extruding a face leaves the original face's edges as a new loop; leaving that face itself in place is what buries an internal wall.