They can be used to simulate the behavior of liquid or gaseous mediums. Vortex Field - is a spiraling fields that can either pull things in or push things out in a spiraling motion. When used with particles you could create a tornado look. The manipulator tools can be used to graphically adjust some of the fields attributes such as location and orientation, provided they are set to be visible. Rigid Body Constraints Rigid body constraints are used to restrict the motion of rigid bodies during a simulation.
Constraints affect only rigid bodies and most affect only active rigid bodies.
You can then specify the type of constraint to be used. There are a number of different constraints that can be used. Nail - A nail constraint is created between an object and a point in space. It acts as though there is a metal rod connecting the object and the point. Hinge - constrains rigid bodies like a pin, only the rotation of the joint is only along one axis, like the hinge on a door.