Bevy MotionGfx

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This page assumes a working Bevy project already exists. If you don’t have one yet, stop here and go set one up first: Bevy’s own Quick Start guide walks through installing Rust and creating a new Bevy project from scratch. Once cargo run opens an empty window for you, come back here.

Add the plugin

cargo add bevy_motiongfx

use bevy::prelude::*;
use bevy_motiongfx::BevyMotionGfxPlugin;
use bevy_motiongfx::prelude::*;

fn main() {
    App::new()
        .add_plugins((DefaultPlugins, BevyMotionGfxPlugin))
        .add_systems(Startup, (setup, build_timeline))
        .run();
}

BevyMotionGfxPlugin adds a MotionGfxManager resource. That’s the only setup it needs: motiongfx.create_builder() gives you a builder that already knows how to animate any Bevy entity’s components.

Set up a scene

fn setup(mut commands: Commands) {
    commands.spawn((Camera3d::default(), Transform::from_xyz(0.0, 0.0, 15.0)));
    commands.spawn((
        DirectionalLight::default(),
        Transform::from_xyz(3.0, 10.0, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));
}

Give it something to animate

fn build_timeline(
    mut commands: Commands,
    mut motiongfx: ResMut<MotionGfxManager>,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    let material = materials.add(StandardMaterial::from_color(Srgba::BLUE));
    let cube = commands
        .spawn((
            Mesh3d(meshes.add(Cuboid::default())),
            MeshMaterial3d(material.clone()),
            Transform::from_xyz(-3.0, 0.0, 0.0),
        ))
        .id();
    // ...
}

cube and material are the two subjects you’ll animate next. Both are ids, which is how every backend addresses a subject.

Describe the animation

Continuing inside the same build_timeline function:

    let mut b = motiongfx.create_builder();
    let track = [
        b.act(cube, path!(<Transform>::translation::x), |x| x + 6.0).play(s(1)),
        b.act(material.id().untyped(), path!(<StandardMaterial>::base_color), |_| {
            Srgba::RED.into()
        })
        .play(s(1)),
    ]
    .ord_all()
    .compile();

    let timeline = b.compile(track);
    commands.spawn((motiongfx.add_timeline(timeline), RealtimePlayer::new().with_playing(true)));
}

motiongfx.create_builder() gives you the same b the rest of these docs talk about. See Actions for what .act()‘s three arguments mean, Ordering for combinators like .ord_all(), and Timeline for what .compile() and b.compile() actually produce.

RealtimePlayer samples the timeline every frame and writes the results back onto your entities. Once it’s spawned, there’s nothing else to call.

Run it

cargo run

A blue cube slides right and turns red over one second.

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