Joints
Joints link rigidbodies together and restrict their movement relative to each other to specific degrees of freedom and ranges. Additionally, they define spring and damping forces to lead the bodies into resting positions and also forces breaking the joint when limits are exceeded.
Joints are extensions of Component, so they are actually attached to nodes that already have a rigidbody attached. To connect nodes in the editor using joints, the node to connect must be a child of the anchor node. The connection is then defined via the name of the child node. Via scripting, it may be possible to use joints without attaching them to a node.
The rigidbodies can slide along one axis runnig through the anchor point between them. (c)
The rigidbodies can rotate against each other along one axis runnig through the anchor point between them, hence forming a hinge or simply a wheel spinning on an axle. (a, b)
Also known as ball and socket. The rigidbodies can freely rotate around the anchor point. (e)
Like spherical, but the torque transmits between the rigidbodies.(d)
Source: https://www.researchgate.net/publication/277332478_State_of_the_Art_in_Prosthetic_Wrists_Commercial_and_Research_Devices.
Permission granted by Dr. Ad Spiers
The rigidbodies are welded together at the anchor point. No movement between them.
Combines prismatic and revolute, picture a cogwheel that can spin and slide on an axle.
Like spherical, but more restricted to simulate joints of skeletons.