In three dimensions, an object has six degrees of freedom. Three degrees of freedom come from translation and an additional three come from orientation. A constraint takes away one or more degrees of freedom. A joint is a type of constraint that limits the degrees of freedom between two objects. There are several common types of joints:
Several simple joints can be combined to create more complex joints. We can use joints to model hinges for doors, ragdolls that represent characters, or to simply stick objects to each other.
