I'm working on a "foldable display" style program to hopefully be used in live stage performances.  For those of you who aren't familiar here's a link to the lauded Johnny Lee and what I'm talking about.

http://www.youtube.com/watch?v=nhSR_6-Y5Kg

I'm setup with a wiimote, got my IR enabled bread board and I've got no problem pulling in my 4 IR points.  My issue is that whenever the wiimote loses track of more than one point it reaquires them in a different order.  So basically I need to setup a function that sorts the four sets of X,Y points and checks to make sure that it resorts if a point gets lost.

For the life of me I can not find a simple way to sort the four sets of points.  I know its possible, and I've seen a variety of people who've done it, but any help would be awesome.  Think basically that someone is randomly giving you the four points of a rectangle and you need to put them in order so you can draw lines between them in some kind of order.

I know there are sort commands for a single array of points but I haven't been able to sort pairs of points.  I thought about sorting based on the distance from the origin, but then I would end up with that value and I don't think I can simply get back to my X,Y coordinates.


Thanks,
Duncan

an idea:

find the centre of the four points

work out the angles between a line from the centre going straight up (possibly involves atan2, most of these things do 8)

sort these angles so you have 4 points ordered clockwise around this centre.

simple case, points at (1,1), (-1,1), (-1,-1) and (1,-1)
origin obviously 0,0

x, y: atan2(x, y) (radians)
1, 1: 0.78539816339745
1, -1: 2.3561944901923
-1, 1: -0.78539816339745
-1, -1: -2.3561944901923

which gives the order (largest first)
(1, -1), (1, 1), (-1, 1), (-1, -1)

(which is the points sorted anticlockwise from bottom right)

any use?