ManipulationNotes
From Simreal
An arm breaks down into three basic areas of motion: the shoulder, elbow, and wrist.
The human arm may seem to be a good place to start, but it describes a very complex motion in three-dimensional space. It is easier to use a simplified model.
The human shoulder consists of a ball-joint (and the scapula, and the clavicle, and so forth) plus a bunch of muscles that conspire to create a wide range of motions. These can be broken down into combinations of three axes of motion: rotation (about 90° forward and 90° reverse rotation through the vertical axis), abduction/adduction (a ìflappingî motion, about 150° upwards and about 75° down across the body), and flexion/extension ("arm swinging," about 180° forwards and 45° backwards).
The human elbow, of course, has a simpler hinge motion.
The wrist is very complex and involves rotations of the radio-ulnar joint that is the forearm, as well as a variety of motions around the wrist proper. For simplicity, it might be considered a ball joint like the shoulder.
