1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58
//! Illustrates how to rotate an object around an axis.
use bevy::prelude::*;
use std::f32::consts::TAU;
// Define a component to designate a rotation speed to an entity.
#[derive(Component)]
struct Rotatable {
speed: f32,
}
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.add_systems(Update, rotate_cube)
.run();
}
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
) {
// Spawn a cube to rotate.
commands.spawn((
PbrBundle {
mesh: meshes.add(Cuboid::default()),
material: materials.add(Color::WHITE),
transform: Transform::from_translation(Vec3::ZERO),
..default()
},
Rotatable { speed: 0.3 },
));
// Spawn a camera looking at the entities to show what's happening in this example.
commands.spawn(Camera3dBundle {
transform: Transform::from_xyz(0.0, 10.0, 20.0).looking_at(Vec3::ZERO, Vec3::Y),
..default()
});
// Add a light source so we can see clearly.
commands.spawn(DirectionalLightBundle {
transform: Transform::from_xyz(3.0, 3.0, 3.0).looking_at(Vec3::ZERO, Vec3::Y),
..default()
});
}
// This system will rotate any entity in the scene with a Rotatable component around its y-axis.
fn rotate_cube(mut cubes: Query<(&mut Transform, &Rotatable)>, timer: Res<Time>) {
for (mut transform, cube) in &mut cubes {
// The speed is first multiplied by TAU which is a full rotation (360deg) in radians,
// and then multiplied by delta_seconds which is the time that passed last frame.
// In other words. Speed is equal to the amount of rotations per second.
transform.rotate_y(cube.speed * TAU * timer.delta_seconds());
}
}