fix examples

examples/2d/rotation.rs

@@ -1,17 +1,19 @@
 //! Demonstrates rotating entities in 2D using quaternions.
 
-use bevy::{math::Vec3Swizzles, prelude::*, time::FixedTimestep};
+use bevy::{math::Vec3Swizzles, prelude::*};
 
-const TIME_STEP: f32 = 1.0 / 60.0;
 const BOUNDS: Vec2 = Vec2::new(1200.0, 640.0);
 
 fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
+        .add_startup_system(|mut fixed_time: ResMut<FixedTime>| {
+            fixed_time.set_steps_per_second(60.0);
+        })
         .add_startup_system(setup)
         .add_system_set(
             SystemSet::new()
-                .with_run_criteria(FixedTimestep::step(TIME_STEP as f64))
+                .with_run_criteria(FixedTimestep::step)
                 .with_system(player_movement_system)
                 .with_system(snap_to_player_system)
                 .with_system(rotate_to_player_system),
@@ -110,6 +112,7 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
 
 /// Demonstrates applying rotation and movement based on keyboard input.
 fn player_movement_system(
+    fixed_time: Res<FixedTime>,
     keyboard_input: Res<Input<KeyCode>>,
     mut query: Query<(&Player, &mut Transform)>,
 ) {
@@ -131,12 +134,12 @@ fn player_movement_system(
     }
 
     // update the ship rotation around the Z axis (perpendicular to the 2D plane of the screen)
-    transform.rotate_z(rotation_factor * ship.rotation_speed * TIME_STEP);
+    transform.rotate_z(rotation_factor * ship.rotation_speed * fixed_time.delta_seconds());
 
     // get the ship's forward vector by applying the current rotation to the ships initial facing vector
     let movement_direction = transform.rotation * Vec3::Y;
     // get the distance the ship will move based on direction, the ship's movement speed and delta time
-    let movement_distance = movement_factor * ship.movement_speed * TIME_STEP;
+    let movement_distance = movement_factor * ship.movement_speed * fixed_time.delta_seconds();
     // create the change in translation using the new movement direction and distance
     let translation_delta = movement_direction * movement_distance;
     // update the ship translation with our new translation delta
@@ -191,6 +194,7 @@ fn snap_to_player_system(
 /// floating point precision loss, so it pays to clamp your dot product value before calling
 /// `acos`.
 fn rotate_to_player_system(
+    fixed_time: Res<FixedTime>,
     mut query: Query<(&RotateToPlayer, &mut Transform), Without<Player>>,
     player_query: Query<&Transform, With<Player>>,
 ) {
@@ -235,7 +239,8 @@ fn rotate_to_player_system(
         let max_angle = forward_dot_player.clamp(-1.0, 1.0).acos(); // clamp acos for safety
 
         // calculate angle of rotation with limit
-        let rotation_angle = rotation_sign * (config.rotation_speed * TIME_STEP).min(max_angle);
+        let rotation_angle =
+            rotation_sign * (config.rotation_speed * fixed_time.delta_seconds()).min(max_angle);
 
         // rotate the enemy to face the player
         enemy_transform.rotate_z(rotation_angle);

examples/3d/transparency_3d.rs

@@ -88,7 +88,7 @@ fn setup(
 ///                when the alpha value goes back below the threshold.
 /// - `Blend`: Object fades in and out smoothly.
 pub fn fade_transparency(time: Res<Time>, mut materials: ResMut<Assets<StandardMaterial>>) {
-    let alpha = (time.time_since_startup().as_secs_f32().sin() / 2.0) + 0.5;
+    let alpha = (time.seconds_since_startup().sin() / 2.0) + 0.5;
     for (_, material) in materials.iter_mut() {
         material.base_color.set_a(alpha);
     }

examples/animation/custom_skinned_mesh.rs

@@ -164,9 +164,7 @@ fn setup(
 /// Animate the joint marked with [`AnimatedJoint`] component.
 fn joint_animation(time: Res<Time>, mut query: Query<&mut Transform, With<AnimatedJoint>>) {
     for mut transform in &mut query {
-        transform.rotation = Quat::from_axis_angle(
-            Vec3::Z,
-            0.5 * PI * time.time_since_startup().as_secs_f32().sin(),
-        );
+        transform.rotation =
+            Quat::from_axis_angle(Vec3::Z, 0.5 * PI * time.seconds_since_startup().sin());
     }
 }

examples/animation/gltf_skinned_mesh.rs

@@ -66,9 +66,7 @@ fn joint_animation(
         // Get `Transform` in the second joint.
         let mut second_joint_transform = transform_query.get_mut(second_joint_entity).unwrap();
 
-        second_joint_transform.rotation = Quat::from_axis_angle(
-            Vec3::Z,
-            0.5 * PI * time.time_since_startup().as_secs_f32().sin(),
-        );
+        second_joint_transform.rotation =
+            Quat::from_axis_angle(Vec3::Z, 0.5 * PI * time.seconds_since_startup().sin());
     }
 }

examples/ecs/component_change_detection.rs

@@ -14,7 +14,7 @@ fn main() {
 }
 
 #[derive(Component, Debug)]
-struct MyComponent(f64);
+struct MyComponent(f32);
 
 fn setup(mut commands: Commands) {
     commands.spawn().insert(MyComponent(0.));

examples/ecs/fixed_timestep.rs

@@ -1,52 +1,55 @@
 //! Shows how to create systems that run every fixed timestep, rather than every tick.
 
-use bevy::{
-    prelude::*,
-    time::{FixedTimestep, FixedTimesteps},
-};
-
-const LABEL: &str = "my_fixed_timestep";
+use bevy::prelude::*;
 
 #[derive(Debug, Hash, PartialEq, Eq, Clone, StageLabel)]
 struct FixedUpdateStage;
 
 fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
-        // this system will run once every update (it should match your screen's refresh rate)
+        .add_startup_system(|mut fixed_time: ResMut<FixedTime>| {
+            fixed_time.set_steps_per_second(10.0);
+        })
+        // Add a system that runs once per update (which should match your screen's refresh rate).
         .add_system(frame_update)
-        // add a new stage that runs twice a second
+        // Add a new stage that runs ten times per second.
         .add_stage_after(
             CoreStage::Update,
             FixedUpdateStage,
             SystemStage::parallel()
-                .with_run_criteria(
-                    FixedTimestep::step(0.5)
-                        // labels are optional. they provide a way to access the current
-                        // FixedTimestep state from within a system
-                        .with_label(LABEL),
-                )
+                .with_run_criteria(FixedTimestep::step)
                 .with_system(fixed_update),
         )
         .run();
 }
 
-fn frame_update(mut last_time: Local<f64>, time: Res<Time>) {
-    info!("update: {}", time.seconds_since_startup() - *last_time);
+fn frame_update(mut last_time: Local<f32>, time: Res<Time>) {
+    info!(
+        "time since last frame_update: {}",
+        time.seconds_since_startup() - *last_time
+    );
     *last_time = time.seconds_since_startup();
 }
 
-fn fixed_update(mut last_time: Local<f64>, time: Res<Time>, fixed_timesteps: Res<FixedTimesteps>) {
+fn fixed_update(
+    mut last_time: Local<f32>,
+    time: Res<Time>,
+    fixed_time: Res<FixedTime>,
+    accumulator: Res<FixedTimestepState>,
+) {
     info!(
-        "fixed_update: {}",
-        time.seconds_since_startup() - *last_time,
+        "time since last fixed_update: {}\n",
+        time.seconds_since_startup() - *last_time
     );
-
-    let fixed_timestep = fixed_timesteps.get(LABEL).unwrap();
+    info!("fixed timestep: {}\n", fixed_time.delta_seconds());
     info!(
-        "  overstep_percentage: {}",
-        fixed_timestep.overstep_percentage()
+        "time accrued toward next fixed_update: {}\n",
+        accumulator.overstep().as_secs_f32()
+    );
+    info!(
+        "time accrued toward next fixed_update (% of timestep): {}",
+        accumulator.overstep_percentage(fixed_time.delta())
     );
-
     *last_time = time.seconds_since_startup();
 }

examples/ecs/iter_combinations.rs

@@ -1,26 +1,27 @@
 //! Shows how to iterate over combinations of query results.
 
-use bevy::{pbr::AmbientLight, prelude::*, render::camera::Camera, time::FixedTimestep};
+use bevy::{pbr::AmbientLight, prelude::*, render::camera::Camera};
 use rand::{thread_rng, Rng};
 
 #[derive(Debug, Hash, PartialEq, Eq, Clone, StageLabel)]
 struct FixedUpdateStage;
 
-const DELTA_TIME: f64 = 0.01;
-
 fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
         .insert_resource(AmbientLight {
             brightness: 0.03,
             ..default()
         })
+        .add_startup_system(|mut fixed_time: ResMut<FixedTime>| {
+            fixed_time.set_steps_per_second(10.0);
+        })
         .add_startup_system(generate_bodies)
         .add_stage_after(
             CoreStage::Update,
             FixedUpdateStage,
             SystemStage::parallel()
-                .with_run_criteria(FixedTimestep::step(DELTA_TIME))
+                .with_run_criteria(FixedTimestep::step)
                 .with_system(interact_bodies)
                 .with_system(integrate),
         )
@@ -54,6 +55,7 @@ fn generate_bodies(
     mut commands: Commands,
     mut meshes: ResMut<Assets<Mesh>>,
     mut materials: ResMut<Assets<StandardMaterial>>,
+    fixed_time: Res<FixedTime>,
 ) {
     let mesh = meshes.add(Mesh::from(shape::Icosphere {
         radius: 1.0,
@@ -103,7 +105,7 @@ fn generate_bodies(
                         rng.gen_range(vel_range.clone()),
                         rng.gen_range(vel_range.clone()),
                         rng.gen_range(vel_range.clone()),
-                    ) * DELTA_TIME as f32,
+                    ) * fixed_time.delta_seconds(),
             ),
         });
     }
@@ -162,8 +164,11 @@ fn interact_bodies(mut query: Query<(&Mass, &GlobalTransform, &mut Acceleration)
     }
 }
 
-fn integrate(mut query: Query<(&mut Acceleration, &mut Transform, &mut LastPos)>) {
-    let dt_sq = (DELTA_TIME * DELTA_TIME) as f32;
+fn integrate(
+    fixed_time: Res<FixedTime>,
+    mut query: Query<(&mut Acceleration, &mut Transform, &mut LastPos)>,
+) {
+    let dt_sq = fixed_time.delta_seconds() * fixed_time.delta_seconds();
     for (mut acceleration, mut transform, mut last_pos) in &mut query {
         // verlet integration
         // x(t+dt) = 2x(t) - x(t-dt) + a(t)dt^2 + O(dt^4)

examples/games/alien_cake_addict.rs

@@ -1,6 +1,7 @@
 //! Eat the cakes. Eat them all. An example 3D game.
 
-use bevy::{ecs::schedule::SystemSet, prelude::*, time::FixedTimestep};
+use bevy::ecs::schedule::ShouldRun;
+use bevy::prelude::*;
 use rand::Rng;
 
 #[derive(Clone, Eq, PartialEq, Debug, Hash)]
@@ -9,9 +10,12 @@ enum GameState {
     GameOver,
 }
 
+struct SpawnTimer(Timer);
+
 fn main() {
     App::new()
         .init_resource::<Game>()
+        .insert_resource(SpawnTimer(Timer::from_seconds(5.0, false)))
         .add_plugins(DefaultPlugins)
         .add_state(GameState::Playing)
         .add_startup_system(setup_cameras)
@@ -29,7 +33,15 @@ fn main() {
         .add_system_set(SystemSet::on_exit(GameState::GameOver).with_system(teardown))
         .add_system_set(
             SystemSet::new()
-                .with_run_criteria(FixedTimestep::step(5.0))
+                .with_run_criteria(|time: Res<Time>, mut timer: ResMut<SpawnTimer>| {
+                    timer.0.tick(time.delta());
+                    if timer.0.finished() {
+                        timer.0.reset();
+                        ShouldRun::Yes
+                    } else {
+                        ShouldRun::No
+                    }
+                })
                 .with_system(spawn_bonus),
         )
         .add_system(bevy::window::close_on_esc)

examples/games/breakout.rs

@@ -3,12 +3,8 @@
 use bevy::{
     prelude::*,
     sprite::collide_aabb::{collide, Collision},
-    time::FixedTimestep,
 };
 
-// Defines the amount of time that should elapse between each physics step.
-const TIME_STEP: f32 = 1.0 / 60.0;
-
 // These constants are defined in `Transform` units.
 // Using the default 2D camera they correspond 1:1 with screen pixels.
 const PADDLE_SIZE: Vec3 = Vec3::new(120.0, 20.0, 0.0);
@@ -55,11 +51,14 @@ fn main() {
         .add_plugins(DefaultPlugins)
         .insert_resource(Scoreboard { score: 0 })
         .insert_resource(ClearColor(BACKGROUND_COLOR))
+        .add_startup_system(|mut fixed_time: ResMut<FixedTime>| {
+            fixed_time.set_steps_per_second(60.0);
+        })
         .add_startup_system(setup)
         .add_event::<CollisionEvent>()
         .add_system_set(
             SystemSet::new()
-                .with_run_criteria(FixedTimestep::step(TIME_STEP as f64))
+                .with_run_criteria(FixedTimestep::step)
                 .with_system(check_for_collisions)
                 .with_system(move_paddle.before(check_for_collisions))
                 .with_system(apply_velocity.before(check_for_collisions))
@@ -310,6 +309,7 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
 }
 
 fn move_paddle(
+    fixed_time: Res<FixedTime>,
     keyboard_input: Res<Input<KeyCode>>,
     mut query: Query<&mut Transform, With<Paddle>>,
 ) {
@@ -325,7 +325,8 @@ fn move_paddle(
     }
 
     // Calculate the new horizontal paddle position based on player input
-    let new_paddle_position = paddle_transform.translation.x + direction * PADDLE_SPEED * TIME_STEP;
+    let new_paddle_position =
+        paddle_transform.translation.x + direction * PADDLE_SPEED * fixed_time.delta_seconds();
 
     // Update the paddle position,
     // making sure it doesn't cause the paddle to leave the arena
@@ -335,10 +336,10 @@ fn move_paddle(
     paddle_transform.translation.x = new_paddle_position.clamp(left_bound, right_bound);
 }
 
-fn apply_velocity(mut query: Query<(&mut Transform, &Velocity)>) {
+fn apply_velocity(fixed_time: Res<FixedTime>, mut query: Query<(&mut Transform, &Velocity)>) {
     for (mut transform, velocity) in &mut query {
-        transform.translation.x += velocity.x * TIME_STEP;
-        transform.translation.y += velocity.y * TIME_STEP;
+        transform.translation.x += velocity.x * fixed_time.delta_seconds();
+        transform.translation.y += velocity.y * fixed_time.delta_seconds();
     }
 }
 

examples/scene/scene.rs

@@ -43,7 +43,7 @@ impl FromWorld for ComponentB {
     fn from_world(world: &mut World) -> Self {
         let time = world.resource::<Time>();
         ComponentB {
-            _time_since_startup: time.time_since_startup(),
+            _time_since_startup: time.elapsed_since_startup(),
             value: "Default Value".to_string(),
         }
     }

examples/stress_tests/bevymark.rs

@@ -5,7 +5,6 @@
 use bevy::{
     diagnostic::{Diagnostics, FrameTimeDiagnosticsPlugin, LogDiagnosticsPlugin},
     prelude::*,
-    time::FixedTimestep,
     window::PresentMode,
 };
 use rand::{thread_rng, Rng};
@@ -43,14 +42,17 @@ fn main() {
             count: 0,
             color: Color::WHITE,
         })
+        .add_startup_system(|mut fixed_time: ResMut<FixedTime>| {
+            fixed_time.set_steps_per_second(5.0);
+        })
         .add_startup_system(setup)
         .add_system(mouse_handler)
         .add_system(movement_system)
         .add_system(collision_system)
         .add_system(counter_system)
         .add_system_set(
             SystemSet::new()
-                .with_run_criteria(FixedTimestep::step(0.2))
+                .with_run_criteria(FixedTimestep::step)
                 .with_system(scheduled_spawner),
         )
         .run();