bevy_easings 0.2.0

Easing plugin for Bevy
Documentation 
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# Bevy Easings

[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT) [![Doc](https://docs.rs/bevy_easings/badge.svg)](https://docs.rs/bevy_easings) [![Crate](https://img.shields.io/crates/v/bevy_easings.svg)](https://crates.io/crates/bevy_easings)


Easings on Bevy components using [interpolation](https://crates.io/crates/interpolation).

## Usage

### System setup

Add the plugin to your app:
```rust
    App::build()
        .add_default_plugins()
        .add_plugin(EasingsPlugin)
        ...
```

### Easing a component to a new value

And then just ease your components to their new state!

```rust
commands
    .spawn(SpriteComponents {
        material: materials.add(Color::RED.into()),
        ..Default::default()
    })
    .with(
        Sprite {
            size: Vec2::new(10., 10.),
            ..Default::default()
        }
        .ease_to(
            Sprite {
                size: Vec2::new(100., 100.),
                ..Default::default()
            },
            EaseFunction::QuadraticIn,
            EasingType::PingPong {
                duration: std::time::Duration::from_secs(1),
                pause: 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.

### Chaining easing

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

```rust
commands
    .spawn(SpriteComponents {
        material: materials.add(Color::RED.into()),
        ..Default::default()
    })
    .with(
        Sprite {
            size: Vec2::new(10., 10.),
            ..Default::default()
        }
        .ease_to(
            Sprite {
                size: Vec2::new(300., 300.),
                ..Default::default()
            },
            EaseFunction::QuadraticIn,
            EasingType::Once {
                duration: std::time::Duration::from_secs(1),
            },
        )
        .ease_to(
            Sprite {
                size: Vec2::new(350., 350.),
                ..Default::default()
            },
            EaseFunction::QuadraticIn,
            EasingType::PingPong {
                duration: std::time::Duration::from_millis(500),
                pause: std::time::Duration::from_millis(200),
            },
        ),
    );
```

## Components Supported

- [`ColorMaterial`](https://docs.rs/bevy/0.2.1/bevy/prelude/struct.ColorMaterial.html)
- [`Sprite`](https://docs.rs/bevy/0.2.1/bevy/prelude/struct.Sprite.html)
- [`Transform`](https://docs.rs/bevy/0.2.1/bevy/prelude/struct.Transform.html)
- [`Style`](https://docs.rs/bevy/0.2.1/bevy/prelude/struct.Style.html)

> :warning: While doing easings on `Handle<ColorMaterial>` is possible (as shown in [this example](https://github.com/mockersf/bevy_extra/blob/master/bevy_easings/examples/colormaterial_color.rs)), it is probably not a good idea as many `ColorMaterial`s will need to be added to the assets and it will slow down your game.

### Custom component support

To be able to ease a component, it needs to implement the traits `Default` and [`Lerp`](https://docs.rs/interpolation/0.2.0/interpolation/trait.Lerp.html). This trait is re-exported by `beavy_easings`.

```rust
#[Derive(Default)]
struct CustomComponent(f32);
impl Lerp for CustomComponent {
    type Scalar = f32;

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

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

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

## Examples

See [examples](https://github.com/mockersf/bevy_extra/tree/master/bevy_easings/examples)

![colormaterial_color](https://raw.githubusercontent.com/mockersf/bevy_extra/master/bevy_easings/examples/colormaterial_color.gif)

![sprite_size](https://raw.githubusercontent.com/mockersf/bevy_extra/master/bevy_easings/examples/sprite_size.gif)

![transform_rotation](https://raw.githubusercontent.com/mockersf/bevy_extra/master/bevy_easings/examples/transform_rotation.gif)

![transform_translation](https://raw.githubusercontent.com/mockersf/bevy_extra/master/bevy_easings/examples/transform_translation.gif)

## Ease Functions

Many [ease functions](https://docs.rs/interpolation/0.2.0/interpolation/enum.EaseFunction.html) 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

## Features

Feature `ease_handle` is enabled by default, and control wether easing on `Handle<ColorMaterial>` is possible or not. Disabling this feature removes a system and a resource that are not used otherwise, the `rand` dependency and remove a `i128` from the `EasingComponent`.