Set Driven Keys are such a Powerful and simple tool. I have been unable to find a comparable tool in any other application. The power of creating relationships between objects without the limitation that it must be a mathematical relationship is incredibly useful. Set Driven Keys are as simple as key-framing an object.

This tool allows for complex relationships to be created by simple keyframing. In addition, it doesn’t limit you to one object.

In this example using one attribute “Wing Flap” , one is able to control three seperate objects, and two rotational axis. Wings typically flap in a circular motion, not just up and down both wings and the body. With another atttribute “Wing Speed”, controlled by an expression, you can animate the butterfly to fly with only one attribute.

Let’s go into more detail.
A common technique to animate a back and forward motion, ie. wings flapping, is to use sin in the expression. Pick an arbitrary number like 20. Creating set driven keys that drive the rotation of the wings up at 20 and down at -20.

Using this technique, the animatable attribute wing speed can be animated up and down making it easier for the animator to focus on one keyable attribute. One keyable attribute controlling at least 6 rotations of three different objects.

This may seem pretty simplistic in nature but you would be amazed how many animators wouldn’t or couldn’t set this initial control up.