Stateless animation, such as bounce easing

摘要

An animation system is described herein that uses a transfer function on the progress of an animation that realistically simulates a bounce behavior. The transfer function maps normalized time and allows a user to specify both a number of bounces and a bounciness factor. Given a normalized time input, the animation system maps the time input onto a unit space where a single unit is the duration of the first bounce. In this coordinate space, the system can find the corresponding bounce and compute the start unit and end unit of this bounce. The system projects the start and end units back onto a normalized time scale and fits these points to a quadratic curve. The quadratic curve can be directly evaluated at the normalized time input to produce a particular output.

主权项

1. A computer-implemented method for statelessly determining a current position of an animated object, the method comprising:
receiving one or more input parameters that specify behavior and a current time of the animated object and a total number of bounces; determining a current bounce among the total number of bounces based on the received input parameters wherein all bounces in the total number of bounces are determinable from the one or more input parameters and the current time and where the one or more input parameters does not include input parameters corresponding to other bounces in the total number of bounces; projecting a start and end time of the current bounce into time space; determining a duration and peak of the current bounce to which to fit a curve; determining the curve that fits the determined start time, end time, and peak of the current bounce; and returning a resulting position based on the determined curve and the received input parameters, wherein the preceding steps are performed by at least one processor.