7482a0d26d
Fixes #15834 ## Migration Guide The APIs of `Time`, `Timer` and `Stopwatch` have been cleaned up for consistency with each other and the standard library's `Duration` type. The following methods have been renamed: - `Stowatch::paused` -> `Stopwatch::is_paused` - `Time::elapsed_seconds` -> `Time::elasped_secs` (including `_f64` and `_wrapped` variants)
133 lines
4.0 KiB
Rust
133 lines
4.0 KiB
Rust
//! This example demonstrates how to use interpolation to make one entity smoothly follow another.
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use bevy::{
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math::{prelude::*, vec3, NormedVectorSpace},
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prelude::*,
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};
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use rand::SeedableRng;
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use rand_chacha::ChaCha8Rng;
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_systems(Startup, setup)
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.add_systems(Update, (move_target, move_follower).chain())
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.run();
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}
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// The sphere that the following sphere targets at all times:
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#[derive(Component)]
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struct TargetSphere;
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// The speed of the target sphere moving to its next location:
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#[derive(Resource)]
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struct TargetSphereSpeed(f32);
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// The position that the target sphere always moves linearly toward:
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#[derive(Resource)]
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struct TargetPosition(Vec3);
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// The decay rate used by the smooth following:
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#[derive(Resource)]
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struct DecayRate(f32);
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// The sphere that follows the target sphere by moving towards it with nudging:
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#[derive(Component)]
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struct FollowingSphere;
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/// The source of randomness used by this example.
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#[derive(Resource)]
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struct RandomSource(ChaCha8Rng);
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fn setup(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut materials: ResMut<Assets<StandardMaterial>>,
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) {
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// A plane:
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commands.spawn((
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Mesh3d(meshes.add(Plane3d::default().mesh().size(12.0, 12.0))),
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MeshMaterial3d(materials.add(Color::srgb(0.3, 0.15, 0.3))),
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Transform::from_xyz(0.0, -2.5, 0.0),
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));
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// The target sphere:
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commands.spawn((
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Mesh3d(meshes.add(Sphere::new(0.3))),
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MeshMaterial3d(materials.add(Color::srgb(0.3, 0.15, 0.9))),
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TargetSphere,
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));
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// The sphere that follows it:
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commands.spawn((
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Mesh3d(meshes.add(Sphere::new(0.3))),
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MeshMaterial3d(materials.add(Color::srgb(0.9, 0.3, 0.3))),
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Transform::from_translation(vec3(0.0, -2.0, 0.0)),
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FollowingSphere,
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));
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// A light:
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commands.spawn((
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PointLight {
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intensity: 15_000_000.0,
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shadows_enabled: true,
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..default()
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},
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Transform::from_xyz(4.0, 8.0, 4.0),
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));
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// A camera:
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commands.spawn((
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Camera3d::default(),
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Transform::from_xyz(-2.0, 3.0, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
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));
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// Set starting values for resources used by the systems:
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commands.insert_resource(TargetSphereSpeed(5.0));
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commands.insert_resource(DecayRate(2.0));
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commands.insert_resource(TargetPosition(Vec3::ZERO));
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commands.insert_resource(RandomSource(ChaCha8Rng::seed_from_u64(68941654987813521)));
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}
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fn move_target(
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mut target: Single<&mut Transform, With<TargetSphere>>,
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target_speed: Res<TargetSphereSpeed>,
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mut target_pos: ResMut<TargetPosition>,
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time: Res<Time>,
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mut rng: ResMut<RandomSource>,
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) {
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match Dir3::new(target_pos.0 - target.translation) {
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// The target and the present position of the target sphere are far enough to have a well-
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// defined direction between them, so let's move closer:
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Ok(dir) => {
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let delta_time = time.delta_secs();
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let abs_delta = (target_pos.0 - target.translation).norm();
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// Avoid overshooting in case of high values of `delta_time`:
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let magnitude = f32::min(abs_delta, delta_time * target_speed.0);
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target.translation += dir * magnitude;
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}
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// The two are really close, so let's generate a new target position:
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Err(_) => {
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let legal_region = Cuboid::from_size(Vec3::splat(4.0));
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*target_pos = TargetPosition(legal_region.sample_interior(&mut rng.0));
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}
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}
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}
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fn move_follower(
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mut following: Single<&mut Transform, With<FollowingSphere>>,
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target: Single<&Transform, (With<TargetSphere>, Without<FollowingSphere>)>,
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decay_rate: Res<DecayRate>,
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time: Res<Time>,
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) {
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let decay_rate = decay_rate.0;
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let delta_time = time.delta_secs();
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// Calling `smooth_nudge` is what moves the following sphere smoothly toward the target.
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following
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.translation
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.smooth_nudge(&target.translation, decay_rate, delta_time);
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}
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