@Override
public int stepSimulation(float timeStep, int maxSubSteps, float fixedTimeStep) {
// apply gravity, predict motion
predictUnconstraintMotion(timeStep);
DispatcherInfo dispatchInfo = getDispatchInfo();
dispatchInfo.timeStep = timeStep;
dispatchInfo.stepCount = 0;
dispatchInfo.debugDraw = getDebugDrawer();
// perform collision detection