[JkWhoSaysNi]

actually it does round to the nearest tile already, the problem is, it cuts the corners because of where the next vertex is. I've attached a better example, without adding more sides to the poly (which i wouldnt know how to calculate anyway) or doing more angles, i'm not sure it's possible to stop it cutting corners.

when the script is finished it'll only ever do the light check once per level, the poly co-ordinates will then be stored. so it's not like it has to do this every time someone enters.