Hi Rogue
The basic rule set here is that the decreasing circle diameter is determined by Sin and the increasing depth of cut is given by Cos (90 down to 0 or a multiple of). Since both use the same numerical value for each pass they stay mathemetically "in sync" (my terminology will probably cause a few comments, but I'm not a mathematician or a machinist).
I think I've probably covered irregular shapes with the program by combining standard geometric shapes , rotations and scaling as a series of jobs.
Point clouds are created by 3D scanners I believe, and are way beyond my capabilities and those of my machine so I'll leave that to CAD/CAM although many don't seem to support it yet.
Gareth