Friday, April 25, 2008

Research Assignment: Bouncing Ball

Research Assignment: Bouncing Ball

Introduction

This assignment looks at how a ball bounces, what techniques are used to make it look realistic and how different weights affect the movement. Below illustrates the path a ball should follow. Each frame has a different shape:


(Idleworm, 2008)


Timing for the Weight
“The timing of the movement of an object defines the weight of the object” (Lasseter, 1987).

This quote means that the way that an object is animated is what provides the illusion of its physical properties. Two objects that are identical in size and shape can have completely different weights by manipulating the timing (Lasseter, 1987).

For heavy objects, the mass is greater and more force is required to act on its movement (Lasseter, 1987). The heavy is slower to accelerate than a light object. For example, a bowling ball requires a large force to get it moving but once moving it tends to keep on moving at the same speed until some force stops it (Lasseter, 1987).


Where the ball makes contact with the ground, there is a 'squash' drawing and it creates the sense of weight (Lauria, 1999). The faster the object moves, the more 'squash' there is (Lauria, 1999).

Volume

The volume of the shape should remain consistent (Lauria, 1999). If the object were to squash or stretch too much it would seem to be growing bigger or smaller. This is a very noticeable effect (Idleworm 2008).

Squash and Stretch

For a falling object such as a ball, the path it moves is in an arc (Lauria, 1999).
At the top of the arc there is a 'slo-in' and at the bottom is the 'slo-out'. There are tick marks on the arc. At the top of the arc, tick marks are close together, at the bottom, they are further apart. Once the ball hits the ground it loses momentum and slows down (Lauria, 1999). The ball then has the 'squash' principle applied to it.

The in-between or break-down drawings create the sense of speed (Lauria, 1999). They use the principle of 'stretch'. At impact the ball goes from 'stretch' to squash' and directly to 'stretch' again. There are no in-between drawings (Lauria, 1999).

Bouncing Ball Animation

I chose a tennis ball for my animation. A tennis ball should usually bounce at least to a height of 50% from where it was dropped originally (About, 2008). The bounce depends on the surface the ball lands on. The surface is partly responsible for he ball’s rebound (About, 2008).

Conclusion

These basic animation principles can be used in other areas of animation. Squash and stretch are quite common.


References

Posted by Quaymberley at 12:34 AM