Crate pareen

Pareen is a small library for parameterized inbetweening.

The intended application is in game programming, where you sometimes have two discrete game states between which you want to transition smoothly for visualization purposes.

Pareen gives you tools for composing animations that are parameterized by time (i.e. mappings from time to some animated value) without constantly having to pass around time variables; it hides the plumbing, so that you need to provide time only once: when evaluating the animation.

Animations are composed similarly to Rust's iterators, so no memory allocations are necessary.

Examples

// An animation returning a constant value
let anim1 = pareen::constant(1.0f64);

// Animations can be evaluated at any time
let value = anim1.eval(0.5);

// Animations can be played in sequence
let anim2 = anim1.seq(0.7, pareen::prop(0.25) + 0.5);

// Animations can be composed and transformed in various ways
let anim3 = anim2
    .lerp(pareen::circle().cos())
    .scale_min_max(5.0, 10.0)
    .backwards(1.0)
    .squeeze(3.0, 0.5..=1.0);

let anim4 = pareen::cubic(&[1.0, 2.0, 3.0, 4.0]) - anim3;

let value = anim4.eval(1.0);
assert_approx_eq!(value, 0.0);

Macros

anim_match

Build an animation that depends on matching some expression.

Structs

Anim	Anim is the main type provided by pareen. It is a wrapper around any type implementing Fun.

Traits

Fun	A Fun represents anything that maps from some type T to another type V.

Functions

circle	Proportionally increase value from zero to 2π.
cond	Return the value of one of two animations depending on a condition.
constant	A constant animation, always returning the same value.
cubic	Evaluate a cubic polynomial in time.
ease_in	Integrate an easing-in function from the easer library.
ease_in_out	Integrate an easing-in-out function from the easer library.
ease_out	Integrate an easing-out function from the easer library.
fun	Turn any function Fn(T) -> V into an Anim.
half_circle	Proportionally increase value from zero to π.
id	An animation that returns time as its value.
lerp	Linearly interpolate between two animations, starting at time zero and finishing at time one.
prop	An animation that returns a value proportional to time.
quarter_circle	Proportionally increase value from zero to π/2.