Adding a bezier curve example (#8194)

# Objective

Examples on how to use the freshly merged `Bezier` struct ( #7653 ) are
missing.

## Solution

- Added a `bezier_curve.rs` example in the `animation/` folder.

---------

Co-authored-by: ira <[email protected]>
Co-authored-by: Aevyrie <[email protected]>

Author: 3 people

Cargo.toml

@@ -722,6 +722,16 @@ 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"

examples/README.md

@@ -144,6 +144,7 @@ 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
 

examples/animation/cubic_curve.rs

@@ -0,0 +1,89 @@
+//! Demonstrates how to work with Cubic curves.
+
+use bevy::{
+    math::{cubic_splines::CubicCurve, vec3},
+    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 points = [[
+        vec3(-6., 2., 0.),
+        vec3(12., 8., 0.),
+        vec3(-12., 8., 0.),
+        vec3(6., 2., 0.),
+    ]];
+
+    // 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(points[0][0]),
+            ..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 t = (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
+        transform.translation = cubic_curve.0.position(t);
+    }
+}