Physics in Animation

     The next section of Mechanics of Motion talked more about how we need to imitate real life, for example, linear movements are rare in nature and we should therefore try to avoid them in animation-

     Also, when a person performs an action, not every part of their body moves at once.  For example, if a guy sits up from a chair, there are many different parts of the body moving at once but in their own ways for their own purpose which all mix together to make the guy exit the chair (overlapping action)

 

     In the top drawing, when the fox turns his body, he doesn't turn every part of himself at once; first his head turns, then his arms start moving, then his hips and legs.  His head turns before his body even starts turning.  In the both drawings, the fox's head turns in an arc rather than a perfectly linear motion to keep it looking more natural and interesting. Lastly, in the bottom drawing, when the fox turns his head (again, in an arc), his ears and fur "drag" because of inertia, then when he stops moving they flop forward a little before losing energy and then sitting still again (follow-through motion)

     To every movement their are different categories of action; for example, during walking the legs stride, push, and stride again in a cycle, which is the primary action.  Their arms also sway from side to side because of the movement of the legs and hips- this is secondary motion.  If the person happens to be wearing a cape, the motion of the cape caused by the primary and secondary motions is known as tertiary action.  If that person happens to carry a freeze ray, this is known as someone about to steal your money.