UN-subdivide

rob kelly nutted this out for me...

put in a subdivided mesh with no history...and get the UN-subdivided equivalent out of it.

he uses a VOPSOP that counts how many neighbors a point has, and if it has 4, then
it can be removed. The trick is to delete every second face first , then check every points neighbor count,
then on another version, delete every second face/prim - but starting from prim #1 as opposed to prim  #0,
then repeat the neighbor count and point removal.

Combining the two results gets you the un-subdivided mesh.

The example file is on odforce here, and shows two methods of achieving the same result.

nice work Rob Kelly ! :)