FYI,
the latest sphere sweep changes have now been carried over into the
official 3.7.1 branch:
https://github.com/POV-Ray/povray/tree/release/v3.7.1
Which means that they'll also be included in the next beta.
(The `experimental/sphere_sweep` branch has been ditched, so don't be
surprised if the link posted earlier leads nowhere now.)
