Arcs in Motion & Squash and Stretch

Introduction to Arcs

Most objects move naturally in an Arc motion, while a few move in linear fashion such as a mechanical piston. So all animation should adhere to this principle of Arcs. One example of object that follows the natural arc motion is a projector connected to the ceiling. The fixed element allows the projector to move in a arc, shown in the picture on the Left.  

The Pendulum

Using a pendulum as an example of natural way of motion using arcs. The black pendulum is showing how the pendulum would move if it was linear. This is wrong and unrealistic, it moves left to right, but not in a swinging manner. Gravity acts on the pendulum forcing it to swing as it connected to a fixed point. Knowing this, i have corrected the middle  (breakdown) frame of the swing, by moving it down to form a natural swing. From all this i can show you 5 frames of the swinging pendulum showing the movement of the arc in more detail. 

Introduction to Squash & Stretch

This the principle that all object which aren't stiff

Even a bouncing ball follows arcs. If a ball follow a straight path it would look unrealistic. 

Different  objects squash and stretch in various way. A light bouncy ball will squash and stretch more then a heavy stone ball. A water droplet squashes and stretches more then a ball.