Rexport angle functions, types from ThreeD.Types
Align cylinder along x-axis, to test rendering

(revert this once rotation is possible)
WIP: initial ThreeD.Vector
WIP: initial ThreeD.Transform

skeleton, has no code
Add 3D-specialized onBasis function
Make envelope, trace on NURBS undefined

Better to throw an error than to give a confusing wrong result.
Use generalized NurbsSurface, specialize to R3
Convert points to homogeneous coördinates in construction of cylinder