Extrusion

An extrusion is a solid volume in 3D space, defined by a "base" face (Face) and an extrusion vector. This solid is defined by the prism generated by extruding the face in the direction and magnitude described by the extrusion vector.

For example, a triangle face, extruded in the direction of the surface normal of that face, yields an Extrusion that represents a triangular prism.

A positive extrusion vector produces a solid whose orientation is front facing out, with all surface normals facing out. A negative extrusion vector extrudes in the direction away from the surface normal of the base face, and produces a solid whose orientation is front facing in, with all surface normals facing in.

Extrusions may possess optional front or back appearances, and may be single or double sided.