On Apr 8, 2013, at 10:05 PM, Mark Coletti wrote: > In other words, I think I resolved your problem by adding the following to your Sim.start(): > > schedule.scheduleRepeating(new Steppable() > { > public void step(SimState state) > { > trailSpace.updateSpatialIndex(); > } > > }); Quick suggested improvement: > schedule.scheduleRepeating(new Steppable() > { > public void step(SimState state) > { > trailSpace.updateSpatialIndex(); > } > > }, -1, 1); This will cause updateSpatialIndex() to happen before anything else each timestep. Sean