QuickTime 4 Reference

Interpolation Tweens

Interpolation tweens are tweens that modify other tweens. The output of an interpolation tween must be a time value, and the time values generated are used in place of the input time values of the tween being modified. For example, you can use a path tween whose data specifies a curve to modify a tween that uses linear interpolation for its algorithm. The starting and ending values for the modified tween remain the same, but the rate at which output values change over time is determined by the shape of the curve.

Once you create an interpolation tween, you can use it to modify any number of other tweens. You can do this by specifying maximum and/or minimum output values of the interpolation tween to match the time values for the tween to be modified. For example, if there is a curve whose shape describes the natural decay rate for a several different sounds, you can can define a single interpolation tween for that curve and apply it, with appropriate maximum and minimum values, to all of the sounds.

An interpolation tween can modify another interpolation tween; the only requirement is that the output of each interpolation tween must be a time value. The ability to define series of interpolations makes it possible to create libraries of standard modifications that can be used together to generate more complex transformations.