Hi everyone!

I'm making a program that collects data from different websites and visualizes it as a tree. In my search for some ideas to the graphics I found this example made using the traer physics library, wich lookes pretty nice.

(I'm not allowed to post websites, but this is were you can find the example.)
cs.princeton.edu/~traer/physics/random_arboretum/index.html

Is there any way to change this example to make it look like a tree? It would need a stable trunk with one fixed particle and a particle system in each end. One for the branches and one for the roots.
Is there a way to constrain the positions of the particles? The roots e.g. shouldn't be able to "grow" over ground.

All answers are appreciated!
Many thanks,
Clara

cs.princeton.edu/~traer/physics/