Bevy Easings

Easings on Bevy components using interpolation.

Usage

System setup

Add the plugin to your app:

use bevy::prelude::*;
use bevy_easings::EasingsPlugin;

fn main() {
    App::new()
        .add_plugins(EasingsPlugin::default());
}

Easing a component to a new value

And then just ease your components to their new state!

use bevy::prelude::*;
use bevy_easings::Ease;

fn my_system(mut commands: Commands){
    commands
        .spawn((
            Sprite {
                ..Default::default()
            },
            Sprite {
                custom_size: Some(Vec2::new(10., 10.)),
                ..Default::default()
            }
            .ease_to(
                Sprite {
                    custom_size: Some(Vec2::new(100., 100.)),
                    ..Default::default()
                },
                bevy_easings::EaseFunction::QuadraticIn,
                bevy_easings::EasingType::PingPong {
                    duration: std::time::Duration::from_secs(1),
                    pause: Some(std::time::Duration::from_millis(500)),
                },
            ),
        ));
}

If the component being eased is not already a component of the entity, the component should first be inserted for the target entity.

Easing to a function-generated target

You can also ease to a target that is generated dynamically from the previous value using a function:

use bevy::prelude::*;
use bevy_easings::Ease;

fn my_system(mut commands: Commands){
    commands
        .spawn((
            Transform::from_scale(Vec3::new(0.1, 0.1, 1.0))
            .ease_to_fn(
                |start| Transform {
                    scale: start.scale * 10.0,
                    ..*start
                },
                bevy_easings::EaseFunction::QuadraticIn,
                bevy_easings::EasingType::PingPong {
                    duration: std::time::Duration::from_secs(1),
                    pause: Some(std::time::Duration::from_millis(500)),
                },
            )
            .ease_to_fn(
                |prev| Transform {
                    scale: prev.scale * 0.5,
                    ..*prev
                },
                bevy_easings::EaseFunction::CubicInOut,
                bevy_easings::EasingType::Once {
                    duration: std::time::Duration::from_secs(2),
                },
            ).with_original_value(),
        ));
}

This is particularly useful to rescue you from repeatly writing initialize code for start status, or chaining animation without worrying about maintaining interior status.

Easing using EaseMethod

The EaseMethod enum can be used to provide easing methods that are not avaliable in EaseFunction.

pub enum EaseMethod {
    /// Follow `EaseFunction`
    EaseFunction(EaseFunction),
    /// Linear interpolation, with no function
    Linear,
    /// Discrete interpolation, eased value will jump from start to end
    Discrete,
    /// Use a custom function to interpolate the value
    CustomFunction(fn(f32) -> f32),
}

This is shown below

use bevy::prelude::*;
use bevy_easings::Ease;

fn my_system(mut commands: Commands){
    commands
        .spawn((
            Sprite {
                ..Default::default()
            },
            Sprite {
                custom_size: Some(Vec2::new(10., 10.)),
                ..Default::default()
            }
            .ease_to(
                Sprite {
                    custom_size: Some(Vec2::new(100., 100.)),
                    ..Default::default()
                },
                bevy_easings::EaseMethod::Linear,
                bevy_easings::EasingType::PingPong {
                    duration: std::time::Duration::from_secs(1),
                    pause: Some(std::time::Duration::from_millis(500)),
                },
            ),
        ));
}

Chaining easing

You can chain easings, if they are not set to repeat they will happen in sequence.

use bevy::prelude::*;
use bevy_easings::Ease;

fn my_system(mut commands: Commands){
    commands
        .spawn((
            Sprite {
                ..Default::default()
            },
            Sprite {
                custom_size: Some(Vec2::new(10., 10.)),
                ..Default::default()
            }
            .ease_to(
                Sprite {
                    custom_size: Some(Vec2::new(300., 300.)),
                    ..Default::default()
                },
                bevy_easings::EaseFunction::QuadraticIn,
                bevy_easings::EasingType::Once {
                    duration: std::time::Duration::from_secs(1),
                },
            )
            .ease_to(
                Sprite {
                    custom_size: Some(Vec2::new(350., 350.)),
                    ..Default::default()
                },
                bevy_easings::EaseFunction::QuadraticIn,
                bevy_easings::EasingType::PingPong {
                    duration: std::time::Duration::from_millis(500),
                    pause: Some(std::time::Duration::from_millis(200)),
                },
            ),
        ));
}

Custom component support

To be able to ease a component, it needs to implement the traits Default and Lerp. This trait is re-exported by beavy_easings.

use bevy::prelude::*;
use bevy_easings::*;

#[derive(Default, Component)]
struct CustomComponent(f32);
impl Lerp for CustomComponent {
    type Scalar = f32;

    fn lerp(&self, other: &Self, scalar: &Self::Scalar) -> Self {
        CustomComponent(interpolation::lerp(&self.0, &other.0, scalar))
    }
}

The basic formula for lerp (linear interpolation) is self + (other - self) * scalar.

Then, the system custom_ease_system::<CustomComponent> needs to be added to the application.

Examples

See examples

Choosing the ease function

When easing colors, pay attention on the color space you are using

Ease Functions

Many ease functions are available:

• QuadraticIn
• QuadraticOut
• QuadraticInOut
• CubicIn
• CubicOut
• CubicInOut
• QuarticIn
• QuarticOut
• QuarticInOut
• QuinticIn
• QuinticOut
• QuinticInOut
• SineIn
• SineOut
• SineInOut
• CircularIn
• CircularOut
• CircularInOut
• ExponentialIn
• ExponentialOut
• ExponentialInOut
• ElasticIn
• ElasticOut
• ElasticInOut
• BackIn
• BackOut
• BackInOut
• BounceIn
• BounceOut
• BounceInOut

Bevy supported version

Bevy	bevy_easings
main	main
0.19	0.19
0.18	0.18
0.17	0.17
0.16	0.16
0.15	0.15
0.14	0.14
0.13	0.14
0.12	0.12
0.11	0.11
0.10	0.10
0.9	0.9
0.8	0.8
0.7	0.7
0.6	0.6
0.5	0.4