Cone extrusion should be in the next release of OpenSCAD, so the value of this is probably going to be pretty marginal.

Quick and dirty cone extrusion module. Should be relatively easy to understand. Willl also do shells.

To make the bevel gear work, you'll want a better computer than mine...

In order to extrude a concave shape, it needs to be decomposed into convex components each of which gets extruded individually.

Shell extrude will produce a cone shell and work better with convex profiles, but is going to take a while in CGAL since it produces a lot of facets and verteces in the seams.

I just added support for 3d path shell extrusion.

Seriously, Thingiverse, why does WIP always keep switching off?!

coneextrude2 uses points/triangles like polyhedron does.