How was Pupper Parade done ?

Hello,

I was reading the description of the Puppet Parade project on CreativeApplications.net ( http://www.creativeapplications.net/openframeworks/puppet-parade-openframeworks/ )
and was trying to figure out how it’s done.

It looks really nice and really responsive.
It seems like binary image skeletonization is done on the outline, but I can’t figure out
how the lines/points are computed from pixels and marked.

Any hints/tips ?