integrated particle system into player positions

src/particle_effect.rs

@@ -1,4 +1,13 @@
 use bevy::{prelude::*, sprite::Mesh2dHandle};
+use rand::Rng;
+use rand_distr::{UnitCircle, Distribution};
+
+pub const POOL_COUNT: usize = 100;
+
+pub const MIN_VELOCITY: f32 = 10.0;
+pub const MAX_VELOCITY: f32 = 100.0;
+pub const VELOCITY_SCALE: f32 = 0.1;
+pub const PARTICLE_EFFECT_RADIUS: f32 = 70.0;
 
 pub struct ParticleEffectPlugin;
 
@@ -6,8 +15,9 @@ impl Plugin for ParticleEffectPlugin {
     fn build(&self, app: &mut App) {
         app
 			.init_resource::<ParticleMesh>()
-            .insert_resource(PoolCount(1000))
-            .add_startup_system(particle_effect_startup);
+            .insert_resource(ParticleEffectResource::new(Vec3::new(10000.0, 10000.0, 0.0)))
+            .add_startup_system(particle_effect_startup)
+			.add_system(particle_effect_system);
     }
 }
 
@@ -18,6 +28,7 @@ pub struct ParticleMesh {
 impl FromWorld for ParticleMesh {
 	fn from_world(world: &mut World) -> Self {
 		let mut meshes = world.get_resource_mut::<Assets<Mesh>>().unwrap();
+
 		Self {
 			square: meshes
 				.add(Mesh::from(shape::Quad {
@@ -29,29 +40,87 @@ impl FromWorld for ParticleMesh {
 	}
 }
 
-pub struct PoolCount(usize);
+#[derive(bevy_inspector_egui::Inspectable)]
+pub struct ParticleEffectResource {
+    pub translation: Vec3,
+	pub prev_translation: Vec3,
+    pub radius_squared: f32,
+	pub color: Color,
+}
 
-#[derive(Component)]
-pub struct ParticleComponent;
+impl ParticleEffectResource {
+	fn new(init_translation: Vec3) -> Self {
+		Self {
+			translation: init_translation,
+			prev_translation: init_translation,
+			radius_squared: PARTICLE_EFFECT_RADIUS * PARTICLE_EFFECT_RADIUS,
+			color: Color::WHITE,
+		}
+	}
+}
+
+#[derive(Default, Component)]
+pub struct ParticleComponent {
+	pub velocity: Vec3,
+}
+
+impl ParticleComponent {
+	pub fn new() -> Self {
+		let mut particle_component: Self = Self::default();
+        particle_component.randomize_velocity(MIN_VELOCITY, MAX_VELOCITY);
+        return particle_component;
+	}
+
+	pub fn randomize_velocity(&mut self, min_velocity: f32, max_velocity: f32) {
+        let random_direction: [f32; 2] = UnitCircle.sample(&mut rand::thread_rng());
+        let random_magnitude: f32 = rand::thread_rng().gen_range(min_velocity .. max_velocity);
+        self.velocity = Vec3::new(random_direction[0], random_direction[1], 0.0) * random_magnitude;
+	}
+}
 
 fn particle_effect_startup(
     mut commands: Commands,
 
 	particle_mesh: Res<ParticleMesh>,
-    pool_count: ResMut<PoolCount>,
 	mut materials: ResMut<Assets<ColorMaterial>>,
 ) {
-    for _p in 0 .. pool_count.0 {
+    for _p in 0 .. POOL_COUNT {
         let color_mesh = ColorMesh2dBundle {
 			mesh: particle_mesh.square.clone(),
 			material: materials.add(ColorMaterial::from(Color::WHITE)),
-            // default to invisible
-            visibility: Visibility {is_visible: false},
 			..default()
 		};
 
         commands
             .spawn_bundle(color_mesh)
-            .insert(ParticleComponent);
+            .insert(ParticleComponent::new());
     }
+}
+
+fn particle_effect_system(
+	mut materials: ResMut<Assets<ColorMaterial>>,
+    mut query: Query<(&mut Transform, &mut ParticleComponent, &Handle<ColorMaterial>)>,
+    mut particle_effect: ResMut<ParticleEffectResource>,
+    time: Res<Time>,
+) {
+    let delta_seconds: f32 = f32::max(0.001, time.delta_seconds());
+	let delta_position: Vec3 = particle_effect.translation - particle_effect.prev_translation;
+	// let overall_velocity: Vec3 = delta_position / delta_seconds;
+	particle_effect.prev_translation = particle_effect.translation;
+
+	for (mut transform, mut particle_component, color_material) in query.iter_mut() {
+        // particle_component.velocity -= overall_velocity * VELOCITY_SCALE;
+        transform.translation += particle_component.velocity * delta_seconds + delta_position;
+
+		let squared_distance: f32 = transform.translation.distance_squared(particle_effect.translation);
+        if squared_distance > particle_effect.radius_squared {
+			transform.translation = particle_effect.translation;
+			particle_component.randomize_velocity(MIN_VELOCITY, MAX_VELOCITY);
+		}
+
+		if let Some(material) = materials.get_mut(color_material) {
+			material.color = particle_effect.color;
+			material.color.set_a((particle_effect.radius_squared - squared_distance) / particle_effect.radius_squared);
+		}
+	}
 }