I have to colliding wires and it seems to me that not the added width is used, but the averaged of both. I created a very simple test to show this. Is there some way around this?
The problem is with the understanding of the “WIDTH”. The width is the diameter of the wire or hair, but when you create a circle to represent that hair, you use the width for the radius. So it's twice as big as it should be. The solution is to use $WIDTH/2 in your copy SOPs.