Monotone mechanisms based on pseudo-triangulations

A pseudo triangulation with one convex hull edge removed is a monotone mechanism: the inter-distances between all pairs of vertices are either all non-decreasing, or all non-increasing (of course, they are fixed where we have bars). Here is such a mechanism in motion, based on a pseudo triangulation of a simple polygon.
Please enable Java for an interactive construction (with Cinderella).

Created by Ileana Streinu and Elif Tosun with Cinderella