Many fine art pieces have been reproduced in digital form. The digital repr
oductions have been used to store and transmit the original work. In contra
st, mobiles, or moving sculptures, such as those designed by Alexander Cald
er cannot be reproduced realistically by photographs and/or static images.
The real characteristics of mobiles come from the motions generated by inte
ractive external for ces applied to their structures. Hence people could no
t fully enjoy them through static images or even static three-dimensional m
odels. We present a virtual mobile system where users can easily control th
e mobile and can feel the impressions that tire artist originally intended
to provide. Virtual winds are generated by blowing on a microphone which th
en exert external forces to the mobile. This microphone interface lets user
s control the mobile while they are watching it through a monitor. We intro
duce a linear time solution for the constraint dynamics and an improved imp
ulse dynamics to speed up the simulation. Using these techniques, toe achie
ve a real-time simulation of the mobile on personal computers. The techniqu
es presented can easily be extended to simulate other interactive dynamics
systems. Copyright (C) 2001 John Wiley & Sons, Ltd.