We have talked a lot about prefractured objects in the previous chapters, and this type is indeed one of the main fields of application for MultiJoints. MultiJoints can be seen as dynamic connections for connecting objects. Let's take a look at a scene with a fractured, rigid body node. Shortly after the beginning of the simulation, the pieces start to break apart, because they are treated as individual nodes without any connection. In order to prevent this, the fragments have to be reconnected and this can be done with MultiJoints. Another, very common, way to use this system is the simulation of different hinges and limbs.
MultiJoints act on forces. Let's stay with the fragmented object: it takes a certain amount of force to prevent the fragments from falling apart. If this force is higher, than the counteracting force which tries to attract the fragments (gravity for example) then the pieces will stick together. If an external event adds another force then some of the connections will break. Typical sources for external forces are daemons, moving fluids, or other interacting bodies.
MultiJoints are not just simple connectors to keep things together, but a complex dynamical system. They can be used for many different applications, like tree-leaf systems, rope-like hinges, plastic deformations of complex, partly broken structures, chains, wheel suspensions, wagons of a train, connected with couplings, and many more.
It is even possible to connect rigid and soft bodies with MultiJoints.
Last but not least, RealFlow offers a system to equip your objects with small motors – the MultiServos. With the help of this node type you are able to turn your setups into physically correct engines. You can accelerate and decelerate your bodies, connect them through MultiJoints, and create complex machines, and accurately behaving technical devices, for example shock absorbers in cars. The behaviour of these simulations is far beyond of what is possible with traditional animation methods. Cars will be able to follow the bumps and pits of a street, MultiServo-driven cable cars cross valleys and rivers, roller coasters follow spectacular courses, and heavy Diesel trains with lots of cargo slowly leave a freight terminal.
With the angular nodes, all kinds of rotating devices can be simulated, for example wind turbines, big wheels, or different types of hubs.