public PhysicsEngine()
{
bodies = new List<RigidBody2D>();
lines = new List<RigidBody2D>();
constraints = new List<Constraint>();
//By default, use a grid partition
partition = new GridPartition(Vector2.Zero, new Vector2(20, 10), 40, 40);
}
public PhysicsEngine(Partition p)
{
partition = p;
}