Yes, my intention when I wrote that was that points 1 and 4 were both positioned on a curve/circle, an equal distance out from vertex C.  But it turns out that that's not really what I was after and so I probably mis-stated it's position (sorry about that)...

The case I really wanted to test was what I was thinking of as a 'hinge effect'.  So it would be the situation where the shortest possible distance from point 1 to the line A-B was the same distance as a (parralell) line through point 4 to the line A-B (so a line through 1-4 would be paralell to line A-B).  In other words, if you imagined the line A-B as a hinge, and tipped the polygon 'up' off a table by lifting vertex C, then points 1 and 4 would move by the exact same amount (point 3 would 'rotate' but not move... point 2 would move less than 1 and 4).

I really should have graphed this out to check the math (I'll probably do that for sanity's sake), but I think it still works.

Cinema4D Plugins (Home of Riptide, Riptide Pro, Undertow, Morph Mill, KyamaSlide and I/Ogre plugins) Poser products Freelance Modelling, Poser Rigging, UV-mapping work for hire.