Module reanchor 

Re-anchoring the rings of a seamless periodic face.

The first healing operation an imported file demanded by name. A STEP face on a periodic surface may arrive bounded by two closed rings and no seam; where the rings’ vertices share an angle, the reader synthesises the seam itself, but where they sit at different angles no seam can join them: the vertices are load-bearing, and 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.