Module reanchor 

Re-anchoring the rings of a seamless periodic face.

A face on a periodic surface may be bounded by two closed rings and no seam. The STEP reader seams such a face itself, splitting one rim on the other’s column where their vertices stand apart; a shape that reaches the healer another way may still hold one whose rings’ vertices sit at different angles, which no seam can join: one of them is in the wrong place. Moving it is surgery: the ring’s closed edge is rebuilt anchored at the aligned angle, and every face that shares the edge (the neighbour on the other side of the ring) is rebuilt to use the new one, or the shell tears exactly where the file was trying to close it.

Functions

reanchor_periodic_rings

Re-anchor misaligned ring vertices so every periodic face can carry a seam.