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example on how to create an animation in code (bevyengine#4399)
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# Objective

- Animation can be used outside of glTF, but are not obvious on how to create them

## Solution

- Add an example creating an animation
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mockersf authored and aevyrie committed Jun 7, 2022
1 parent 6da4b80 commit f1a6f4d
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4 changes: 4 additions & 0 deletions Cargo.toml
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Expand Up @@ -241,6 +241,10 @@ path = "examples/3d/wireframe.rs"
name = "animated_fox"
path = "examples/animation/animated_fox.rs"

[[example]]
name = "animated_transform"
path = "examples/animation/animated_transform.rs"

[[example]]
name = "custom_skinned_mesh"
path = "examples/animation/custom_skinned_mesh.rs"
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1 change: 1 addition & 0 deletions examples/README.md
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Expand Up @@ -123,6 +123,7 @@ Example | File | Description
Example | File | Description
--- | --- | ---
`animated_fox` | [`animation/animated_fox.rs`](./animation/animated_fox.rs) | Plays an animation from a skinned glTF.
`animated_transform` | [`animation/animated_transform.rs`](./animation/animated_transform.rs) | Create and play an animation defined by code that operates on the `Transform` component.
`custom_skinned_mesh` | [`animation/custom_skinned_mesh.rs`](./animation/custom_skinned_mesh.rs) | Skinned mesh example with mesh and joints data defined in code.
`gltf_skinned_mesh` | [`animation/gltf_skinned_mesh.rs`](./animation/gltf_skinned_mesh.rs) | Skinned mesh example with mesh and joints data loaded from a glTF file.

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141 changes: 141 additions & 0 deletions examples/animation/animated_transform.rs
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use std::f32::consts::{FRAC_PI_2, PI};

use bevy::prelude::*;

fn main() {
App::new()
.add_plugins(DefaultPlugins)
.insert_resource(AmbientLight {
color: Color::WHITE,
brightness: 1.0,
})
.add_startup_system(setup)
.run();
}

fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
mut animations: ResMut<Assets<AnimationClip>>,
) {
// Camera
commands.spawn_bundle(PerspectiveCameraBundle {
transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
..default()
});

// The animation API uses the `Name` component to target entities
let planet = Name::new("planet");
let orbit_controller = Name::new("orbit_controller");
let satellite = Name::new("satellite");

// Creating the animation
let mut animation = AnimationClip::default();
// A curve can modify a single part of a transform, here the translation
animation.add_curve_to_path(
EntityPath {
parts: vec![planet.clone()],
},
VariableCurve {
keyframe_timestamps: vec![0.0, 1.0, 2.0, 3.0, 4.0],
keyframes: Keyframes::Translation(vec![
Vec3::new(1.0, 0.0, 1.0),
Vec3::new(-1.0, 0.0, 1.0),
Vec3::new(-1.0, 0.0, -1.0),
Vec3::new(1.0, 0.0, -1.0),
// in case seamless looping is wanted, the last keyframe should
// be the same as the first one
Vec3::new(1.0, 0.0, 1.0),
]),
},
);
// Or it can modify the rotation of the transform.
// To find the entity to modify, the hierarchy will be traversed looking for
// an entity with the right name at each level
animation.add_curve_to_path(
EntityPath {
parts: vec![planet.clone(), orbit_controller.clone()],
},
VariableCurve {
keyframe_timestamps: vec![0.0, 1.0, 2.0, 3.0, 4.0],
keyframes: Keyframes::Rotation(vec![
Quat::from_axis_angle(Vec3::Y, 0.0),
Quat::from_axis_angle(Vec3::Y, FRAC_PI_2),
Quat::from_axis_angle(Vec3::Y, PI),
Quat::from_axis_angle(Vec3::Y, 3.0 * FRAC_PI_2),
Quat::from_axis_angle(Vec3::Y, 0.0),
]),
},
);
// If a curve in an animation is shorter than the other, it will not repeat
// until all other curves are finished. In that case, another animation should
// be created for each part that would have a different duration / period
animation.add_curve_to_path(
EntityPath {
parts: vec![planet.clone(), orbit_controller.clone(), satellite.clone()],
},
VariableCurve {
keyframe_timestamps: vec![0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0],
keyframes: Keyframes::Scale(vec![
Vec3::splat(0.8),
Vec3::splat(1.2),
Vec3::splat(0.8),
Vec3::splat(1.2),
Vec3::splat(0.8),
Vec3::splat(1.2),
Vec3::splat(0.8),
Vec3::splat(1.2),
Vec3::splat(0.8),
]),
},
);
// There can be more than one curve targeting the same entity path
animation.add_curve_to_path(
EntityPath {
parts: vec![planet.clone(), orbit_controller.clone(), satellite.clone()],
},
VariableCurve {
keyframe_timestamps: vec![0.0, 1.0, 2.0, 3.0, 4.0],
keyframes: Keyframes::Rotation(vec![
Quat::from_axis_angle(Vec3::Y, 0.0),
Quat::from_axis_angle(Vec3::Y, FRAC_PI_2),
Quat::from_axis_angle(Vec3::Y, PI),
Quat::from_axis_angle(Vec3::Y, 3.0 * FRAC_PI_2),
Quat::from_axis_angle(Vec3::Y, 0.0),
]),
},
);

// Create the animation player, and set it to repeat
let mut player = AnimationPlayer::default();
player.play(animations.add(animation)).repeat();

// Create the scene that will be animated
// First entity is the planet
commands
.spawn_bundle(PbrBundle {
mesh: meshes.add(Mesh::from(shape::Icosphere::default())),
material: materials.add(Color::rgb(0.8, 0.7, 0.6).into()),
..default()
})
// Add the Name component, and the animation player
.insert_bundle((planet, player))
.with_children(|p| {
// This entity is just used for animation, but doesn't display anything
p.spawn_bundle(TransformBundle { ..default() })
// Add the Name component
.insert(orbit_controller)
.with_children(|p| {
// The satellite, placed at a distance of the planet
p.spawn_bundle(PbrBundle {
transform: Transform::from_xyz(1.5, 0.0, 0.0),
mesh: meshes.add(Mesh::from(shape::Cube { size: 0.5 })),
material: materials.add(Color::rgb(0.3, 0.9, 0.3).into()),
..default()
})
// Add the Name component
.insert(satellite);
});
});
}

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