A Side is a set of Wires, to which is associated a surface. The first wire is the external one, the next wires define optional holes. These sides are used directly in 2D modelling, or gathered in Skins in 3D.

side = sideset.add( Side(number, [wire1, wire2, wire3, ...]) )
side.setSurface(surface)

• The normal of a side is the normal to its surface.
• For rigid contact, the normal must point towards the inside of the matter (as for curves in 2D).
• For sides defined by their surface only (surface of revolution for example), it is allowed to define the face with a setSurface (the face does not have any wires, and is limited by the parameters $(u,v) = (0,0) \rightarrow (1,1)$ of the surface.