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Adding a bezier curve example #8194

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10 changes: 10 additions & 0 deletions Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -713,6 +713,16 @@ description = "Create and play an animation defined by code that operates on the
category = "Animation"
wasm = true

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

[package.metadata.example.cubic_curve]
name = "Cubic Curve"
description = "Bezier curve example showing a cube following a cubic curve"
category = "Animation"
wasm = true

[[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
Original file line number Diff line number Diff line change
Expand Up @@ -143,6 +143,7 @@ Example | Description
--- | ---
[Animated Fox](../examples/animation/animated_fox.rs) | Plays an animation from a skinned glTF
[Animated Transform](../examples/animation/animated_transform.rs) | Create and play an animation defined by code that operates on the `Transform` component
[Cubic Curve](../examples/animation/cubic_curve.rs) | Bezier curve example showing a cube following a cubic curve
[Custom Skinned Mesh](../examples/animation/custom_skinned_mesh.rs) | Skinned mesh example with mesh and joints data defined in code
[glTF Skinned Mesh](../examples/animation/gltf_skinned_mesh.rs) | Skinned mesh example with mesh and joints data loaded from a glTF file

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93 changes: 93 additions & 0 deletions examples/animation/cubic_curve.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,93 @@
//! Demonstrates how to work with Cubic curves.
//!

use bevy::{math::cubic_splines::CubicCurve, prelude::*};

#[derive(Component)]
pub struct Curve(CubicCurve<Vec3>);

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

fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
) {
// Define your control points
// These points will define the curve
// You can learn more about bezier curves here
// https://en.wikipedia.org/wiki/B%C3%A9zier_curve
let control_point1 = Vec3::new(-6., 2., 0.);
let control_point2 = Vec3::new(12., 8., 0.);

let control_point3 = Vec3::new(-12., 8., 0.);
let control_point4 = Vec3::new(6., 2., 0.);

let points = [[
control_point1,
control_point2,
control_point3,
control_point4,
]];
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// Make a CubicCurve
let bezier = Bezier::new(points).to_curve();

// Spawning a cube to experiment on
commands.spawn((
PbrBundle {
mesh: meshes.add(shape::Cube::default().into()),
material: materials.add(Color::ORANGE.into()),
transform: Transform::from_translation(control_point1),
..default()
},
Curve(bezier),
));

// Some light to see something
commands.spawn(PointLightBundle {
point_light: PointLight {
intensity: 9000.,
range: 100.,
shadows_enabled: true,
..default()
},
transform: Transform::from_xyz(8., 16., 8.),
..default()
});

// ground plane
commands.spawn(PbrBundle {
mesh: meshes.add(shape::Plane::from_size(50.).into()),
material: materials.add(Color::SILVER.into()),
..default()
});

// The camera
commands.spawn(Camera3dBundle {
transform: Transform::from_xyz(0., 6., 12.).looking_at(Vec3::new(0., 3., 0.), Vec3::Y),
..default()
});
}

pub fn animate_cube(
time: Res<Time>,
mut query: Query<(&mut Transform, &Curve)>,
mut gizmos: Gizmos,
) {
let step = (time.elapsed_seconds().sin() + 1.) / 2.;

for (mut transform, cubic_curve) in &mut query {
// Draw the curve
gizmos.linestrip(cubic_curve.0.iter_positions(50), Color::WHITE);
// position takes a point from the curve where 0 is the initial point
// and 1 is the last point
Comment on lines +85 to +86
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@aevyrie aevyrie Mar 29, 2023

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I'd remove this comment to avoid duplicating the docs. I'd also prefer using t instead of step, as it is the standard input into a parametric function, and is what is used in the docs: https://docs.rs/bevy/latest/bevy/math/cubic_splines/struct.CubicCurve.html#method.position

As above, this is a pretty minor nit, and could be ignored.

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Good point for t instead of step, however, I'd keep the comment even though it's duplicating the docs to avoid any confusion the user would have.

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I very much like keeping the duplicative comment here :) The information is important and relevant here.

transform.translation = cubic_curve.0.position(step);
}
}