Rate functions

Rate functions are, as their name implies, functions, normalized functions, whose domain goes from 0 to 1 and the range must be within the interval \([0,1]\), but nothing prevents it from starting or ending in those limits.

\(0\) means \(0\%\) of run_time and \(1\) means \(100\%\) of run_time, and run_time is the total duration of the animation.

Some rate functions that are already predefined are explained below.

The following animation explains how the rate functions work. Each animation starts from a state of \(0\%\) complete to \(100\%\) complete, the rate functions change the behavior of that increment.

These functions are used to change the way class animations work.

Each class animation has a predefined rate function, for example, the Write animation has linear as the default rate_func. But they are easy to change.

If we play around with the behavior of the function we can do something like this:

def construct(self):
    text = Text("Smooth")
    text.set(width=config.frame_width-1)

    self.play(
        Write(text,rate_func=smooth)
    )
    self.wait()
    self.play(
        # inverse smooth function
        Write(text,rate_func=lambda t: smooth(1-t))
    )
    self.wait()

Inside the Scene.play method you can specify a rate_func and run_time for all animations, or you can specify each rate_func and run_time for each animation.

# For all Animations
self.play(
    Animation1(...),
    Animation2(...),
    Animation3(...),
    ....
    AnimationN(...),
    rate_func=some_rate_func,
    run_time=some_run_time,
)

# For each animation
self.play(
    Animation1(...,rate_func=rf1,run_time=rt1),
    Animation2(...,rate_func=rf2,run_time=rt2),
    Animation3(...,rate_func=rf3,run_time=rt3),
    ....
    AnimationN(...,rate_func=rfN,run_time=rtN),
)

In short, rate_func is the behavior of the animation, and run_time is the duration of the animation. And they can be defined for each (class) animation or for all animations within a Scene.play.