Add ant sprite animation + improve random walk

Ants now randomize the velocity derivative instead of the velocity
directly

src/components/ant.rs

@@ -1,5 +1,11 @@
-use super::common::{Position, RandomizedVelocity};
+use super::common::{
+    AnimationIndices, AnimationTimer, Position, RandomizedVelocityChange, Velocity,
+    VelocityChangeTimer,
+};
+use crate::{ANT_ANIMATION_SPEED, VELOCITY_CHANGE_PERIOD, VELOCITY_CHANGE_SCALE};
 use bevy::prelude::*;
+use rand::Rng;
+use std::f32::consts::PI;
 
 /// This bundle represents the ant entity.
 /// The ``state`` determines the ant's behavior, it stores its current ``position``
@@ -13,7 +19,14 @@ use bevy::prelude::*;
 pub struct AntBundle {
     pub state: AntState,
     pub position: Position,
-    pub velocity: RandomizedVelocity,
+    pub velocity: Velocity,
+    pub velocity_change: RandomizedVelocityChange,
+    // TODO: This timer is only needed once
+    pub velocity_change_timer: VelocityChangeTimer,
+    pub texture_atlas: TextureAtlas,
+    pub animation_indices: AnimationIndices,
+    // TODO: This timer is only needed once
+    pub animation_timer: AnimationTimer,
 
     // These are not components, but other bundles of components. Those can be nested.
     pub sprite: SpriteBundle,
@@ -42,17 +55,37 @@ pub enum AntState {
 // The "impl" keyword allows us to implement functions in a struct's namespace, i.e. "methods"
 impl AntBundle {
     /// Instantiate a new ``AntBundle`` with a color and a starting position.
-    pub fn new(position: Vec2, color: Color) -> Self {
+    pub fn new(
+        position: Vec2,
+        texture: Handle<Image>,
+        texture_atlas: TextureAtlas,
+        animation_indices: AnimationIndices,
+        scale: Vec2,
+    ) -> Self {
         Self {
             state: AntState::Searching,
             position: Position(position),
-            velocity: RandomizedVelocity(Vec2::ZERO),
+            velocity: Velocity(rand::thread_rng().gen_range(-PI..PI)),
+            velocity_change: RandomizedVelocityChange(
+                rand::thread_rng().gen_range(-1.0..1.0) * VELOCITY_CHANGE_SCALE,
+            ),
+            velocity_change_timer: VelocityChangeTimer(Timer::from_seconds(
+                VELOCITY_CHANGE_PERIOD,
+                TimerMode::Repeating,
+            )),
+            texture_atlas,
+            animation_indices,
+            animation_timer: AnimationTimer(Timer::from_seconds(
+                ANT_ANIMATION_SPEED,
+                TimerMode::Repeating,
+            )),
             sprite: SpriteBundle {
                 transform: Transform {
-                    scale: Vec3::new(20., 20., 20.),
+                    translation: position.extend(0.),
+                    scale: scale.extend(1.),
                     ..default()
                 },
-                sprite: Sprite { color, ..default() },
+                texture,
                 ..default()
             },
         }

src/components/common.rs

@@ -4,7 +4,19 @@ use bevy::prelude::*;
 pub struct Position(pub Vec2);
 
 #[derive(Component)]
-pub struct Velocity(pub Vec2);
+pub struct Velocity(pub f32);
 
 #[derive(Component)]
-pub struct RandomizedVelocity(pub Vec2);
+pub struct RandomizedVelocityChange(pub f32);
+
+#[derive(Component)]
+pub struct AnimationIndices {
+    pub first: usize,
+    pub last: usize,
+}
+
+#[derive(Component)]
+pub struct AnimationTimer(pub Timer);
+
+#[derive(Component)]
+pub struct VelocityChangeTimer(pub Timer);

src/main.rs

@@ -4,24 +4,33 @@ mod systems;
 use bevy::prelude::*;
 use std::f32::consts::PI;
 use systems::{
-    random_walk::{random_walk_system, randomized_velocity_system, wall_avoidance_system},
+    ant::{
+        animation_system, position_update_system, randomized_velocity_change_system,
+        randomized_velocity_system, wall_avoidance_system,
+    },
     startup::{hello_ants_system, setup_system},
 };
 
 // TODO: Use Settings Resource
-const MIN_POSITION: Vec2 = Vec2::ZERO;
-const MAX_POSITION: Vec2 = Vec2::new(500., 500.);
+const MIN_POSITION: Vec2 = Vec2::splat(-450.);
+const MAX_POSITION: Vec2 = Vec2::splat(450.);
 
-const ANT_COUNT: u32 = 25;
-const ANT_SPEED: f32 = 0.75;
-const RANDOM_WALK_CONE: f32 = PI / 180. * 20.;
+const ANT_COUNT: u32 = 200;
+const ANT_SPEED: f32 = 0.5;
+const ANT_ANIMATION_SPEED: f32 = 1. / 62.;
+const ANT_SCALE: f32 = 0.15;
+
+const VELOCITY_CHANGE_SCALE: f32 = PI / 180. * 1.; // Single degree
+const VELOCITY_CHANGE_MAX: f32 = PI / 180. * 0.5;
+const VELOCITY_CHANGE_PERIOD: f32 = 0.5;
 
 /// The app's entrypoint.
 fn main() {
     let mut app = App::new();
 
     // The DefaultPlugins contain the "Window" plugin.
-    app.add_plugins(DefaultPlugins);
+    // ImagePlugin::default_nearest() is supposed to prevent blurry sprites.
+    app.add_plugins(DefaultPlugins.set(ImagePlugin::default_nearest()));
 
     // Sets the color used to clear the screen, i.e. the background color.
     app.insert_resource(ClearColor(Color::srgb(0.9, 0.9, 0.9)));
@@ -38,9 +47,11 @@ fn main() {
     app.add_systems(
         FixedUpdate,
         (
+            randomized_velocity_change_system,
             randomized_velocity_system,
             wall_avoidance_system,
-            random_walk_system,
+            position_update_system,
+            animation_system,
         )
             .chain(),
     );

src/systems/ant.rs

@@ -0,0 +1,96 @@
+use crate::{
+    components::common::{
+        AnimationIndices, AnimationTimer, Position, RandomizedVelocityChange, Velocity,
+        VelocityChangeTimer,
+    },
+    ANT_SPEED, MAX_POSITION, MIN_POSITION, VELOCITY_CHANGE_MAX, VELOCITY_CHANGE_SCALE,
+};
+use bevy::prelude::*;
+use rand::Rng;
+use std::f32::consts::PI;
+
+/// Randomizes the ``RandomizeVelocityChange`` components.
+#[allow(clippy::needless_pass_by_value)]
+pub fn randomized_velocity_change_system(
+    mut query: Query<(&mut RandomizedVelocityChange, &mut VelocityChangeTimer)>,
+    time: Res<Time>,
+) {
+    for (mut velocity_change, mut timer) in &mut query {
+        timer.0.tick(time.delta());
+
+        if timer.0.just_finished() {
+            velocity_change.0 += rand::thread_rng().gen_range(-1.0..1.0) * VELOCITY_CHANGE_SCALE;
+            velocity_change.0 = velocity_change
+                .0
+                .clamp(-VELOCITY_CHANGE_MAX, VELOCITY_CHANGE_MAX);
+        }
+    }
+}
+
+/// Updates the ``Velocity`` components for entities that have a ``RandomizedVelocityChange``.
+pub fn randomized_velocity_system(
+    mut query: Query<(&mut Transform, &mut Velocity, &RandomizedVelocityChange)>,
+) {
+    for (mut transform, mut velocity, velocity_change) in &mut query {
+        velocity.0 += velocity_change.0;
+        transform.rotation = Quat::from_euler(EulerRot::XYZ, 0., 0., velocity.0 - PI / 2.);
+    }
+}
+
+/// Updates ``Position`` and ``Transform`` components of entities that also have
+/// the ``RandomizedVelocity`` component, like an ``Ant``.
+pub fn position_update_system(
+    // We query for each entity that has a Position, Transform and Velocity component.
+    // The Transform component comes from the SpriteBundle.
+    mut query: Query<(&mut Position, &mut Transform, &Velocity)>,
+) {
+    for (mut position, mut transform, velocity) in &mut query {
+        let new_position: Vec2 = position.0 + Vec2::from_angle(velocity.0).normalize() * ANT_SPEED;
+
+        transform.translation = new_position.clamp(MIN_POSITION, MAX_POSITION).extend(0.);
+        position.0 = new_position.clamp(MIN_POSITION, MAX_POSITION);
+    }
+}
+
+/// Sets an ant's velocity perpendicular to a wall, if touched.
+pub fn wall_avoidance_system(mut query: Query<(&Position, &mut Velocity)>) {
+    let touches_left_wall = |position: Vec2| -> bool { position.x <= MIN_POSITION.x };
+    let touches_right_wall = |position: Vec2| -> bool { position.x >= MAX_POSITION.x };
+    let touches_bottom_wall = |position: Vec2| -> bool { position.y <= MIN_POSITION.y };
+    let touches_top_wall = |position: Vec2| -> bool { position.y >= MAX_POSITION.y };
+
+    for (position, mut velocity) in &mut query {
+        let mut new_velocity: f32 = velocity.0;
+
+        if touches_left_wall(position.0) {
+            new_velocity = 0.;
+        } else if touches_right_wall(position.0) {
+            new_velocity = PI;
+        } else if touches_bottom_wall(position.0) {
+            new_velocity = PI / 2.;
+        } else if touches_top_wall(position.0) {
+            new_velocity = 3. * PI / 2.;
+        }
+
+        velocity.0 = new_velocity;
+    }
+}
+
+/// Animates the ants by incrementing their ``TextureAtlas`` indices, based on a timer.
+#[allow(clippy::needless_pass_by_value)]
+pub fn animation_system(
+    mut query: Query<(&AnimationIndices, &mut AnimationTimer, &mut TextureAtlas)>,
+    time: Res<Time>,
+) {
+    for (indices, mut timer, mut atlas) in &mut query {
+        timer.0.tick(time.delta());
+
+        if timer.0.just_finished() {
+            atlas.index = if atlas.index == indices.last {
+                indices.first
+            } else {
+                atlas.index + 1
+            };
+        }
+    }
+}

src/systems/mod.rs

@@ -1,2 +1,2 @@
-pub mod random_walk;
+pub mod ant;
 pub mod startup;

src/systems/random_walk.rs

@@ -1,65 +0,0 @@
-use crate::{
-    components::common::{Position, RandomizedVelocity},
-    ANT_SPEED, MAX_POSITION, MIN_POSITION, RANDOM_WALK_CONE,
-};
-use bevy::prelude::*;
-
-/// Randomizes the ``RandomizedVelocity`` components of entities that have them.
-#[allow(clippy::needless_pass_by_value)] // I can't specify &Res<Time>, so pass by value
-pub fn randomized_velocity_system(mut query: Query<&mut RandomizedVelocity>) {
-    for mut velocity in &mut query {
-        let mut new_velocity: Vec2 = Vec2::from_angle(
-            // We first multiply with CONE to get the angle-delta to [0, CONE].
-            // Then, we subtract CONE/2 to bring the angle-delta to [-CONE/2, CONE/2].
-            // Lastly, we add the angle-delta to the current angle.
-            // This should vary the direction in a front-facing CONE-degree cone.
-            rand::random::<f32>().mul_add(
-                RANDOM_WALK_CONE,
-                velocity.0.to_angle() - RANDOM_WALK_CONE / 2.,
-            ),
-        );
-        new_velocity = new_velocity.normalize() * ANT_SPEED;
-
-        velocity.0 = new_velocity;
-    }
-}
-
-/// Updates ``Position`` and ``Transform`` components of entities that also have
-/// the ``RandomizedVelocity`` component, like an ``Ant``.
-#[allow(clippy::module_name_repetitions)]
-pub fn random_walk_system(
-    // We query for each entity that has a Position, Transform and Velocity component.
-    // The Transform component comes from the SpriteBundle.
-    mut query: Query<(&mut Position, &mut Transform, &RandomizedVelocity)>,
-) {
-    for (mut position, mut transform, velocity) in &mut query {
-        let new_position: Vec2 = position.0 + velocity.0;
-
-        transform.translation = new_position.clamp(MIN_POSITION, MAX_POSITION).extend(0.);
-        position.0 = new_position.clamp(MIN_POSITION, MAX_POSITION);
-    }
-}
-
-/// Sets an ant's velocity perpendicular to a wall, if touched.
-pub fn wall_avoidance_system(mut query: Query<(&Position, &mut RandomizedVelocity)>) {
-    let touches_left_wall = |position: Vec2| -> bool { position.x <= 0. };
-    let touches_right_wall = |position: Vec2| -> bool { position.x >= MAX_POSITION.x };
-    let touches_bottom_wall = |position: Vec2| -> bool { position.y <= 0. };
-    let touches_top_wall = |position: Vec2| -> bool { position.y >= MAX_POSITION.y };
-
-    for (position, mut velocity) in &mut query {
-        let mut new_velocity: Vec2 = velocity.0;
-
-        if touches_left_wall(position.0) {
-            new_velocity = Vec2::new(1., 0.);
-        } else if touches_right_wall(position.0) {
-            new_velocity = Vec2::new(-1., 0.);
-        } else if touches_bottom_wall(position.0) {
-            new_velocity = Vec2::new(0., 1.);
-        } else if touches_top_wall(position.0) {
-            new_velocity = Vec2::new(0., -1.);
-        }
-
-        velocity.0 = new_velocity;
-    }
-}

src/systems/startup.rs

@@ -1,5 +1,9 @@
-use crate::{components::ant::AntBundle, ANT_COUNT};
+use crate::{
+    components::{ant::AntBundle, common::AnimationIndices},
+    ANT_COUNT, ANT_SCALE, MAX_POSITION,
+};
 use bevy::prelude::*;
+use rand::Rng;
 
 /// Signal that the app has started by printing a message to the terminal.
 pub fn hello_ants_system() {
@@ -7,14 +11,36 @@ pub fn hello_ants_system() {
 }
 
 /// Prepares the environment before the Update schedule by spawning required entities.
-pub fn setup_system(mut commands: Commands) {
+#[allow(clippy::needless_pass_by_value)]
+pub fn setup_system(
+    mut commands: Commands,
+    asset_server: Res<AssetServer>,
+    mut texture_atlas_layouts: ResMut<Assets<TextureAtlasLayout>>,
+) {
     // Using the default camera, world space coordinates correspond 1:1 with screen pixels.
     // The point (0, 0) is in the center of the screen.
     commands.spawn(Camera2dBundle::default());
 
     // Spawn cute ants
+    // https://github.com/bevyengine/bevy/blob/latest/examples/2d/sprite_sheet.rs
+    // TODO: Some weird cloning here
+    let texture: Handle<Image> = asset_server.load("sprites/ant_walk_anim.png");
+    let layout = TextureAtlasLayout::from_grid(UVec2::new(202, 248), 8, 8, None, None);
+    let texture_atlas_layout = texture_atlas_layouts.add(layout);
     for _ in 0..ANT_COUNT {
-        commands.spawn(AntBundle::new(Vec2::new(0., 0.), Color::srgb(1., 0., 0.)));
+        let animation_indices = AnimationIndices { first: 0, last: 61 };
+        let texture_atlas = TextureAtlas {
+            layout: texture_atlas_layout.clone(),
+            index: rand::thread_rng().gen_range(animation_indices.first..=animation_indices.last),
+        };
+
+        commands.spawn(AntBundle::new(
+            Vec2::ZERO,
+            texture.clone(),
+            texture_atlas,
+            animation_indices,
+            Vec2::splat(ANT_SCALE),
+        ));
     }
     println!("Spawned {ANT_COUNT} cute ants 😍");
 }