Answer
A 3D curve can be created in space or lie on a geometrical element, or both. When the curve lies on a geometrical element, associativity can be kept. It is also possible to edit, delete or add points when creating the curve, or after. A 3D curve is a very fast and flexible tool which is really different from a "Spline".
- route electrical wires,
- work with Bezier Nurbs,
- create a guide curve for a sweep or a rib.
From the following document, you will learn new possibilities about 3D curve from "FreeStyle" workbench.
