no more overlapping balls!

src/main.rs

@@ -14,6 +14,7 @@ use rapier2d::{
 const WINDOW_WIDTH: u32 = 512;
 const WINDOW_HEIGHT: u32 = WINDOW_WIDTH;
 const PARTICLE_COUNT: u32 = 200;
+const PARTICLE_SIZE: f32 = 5.;
 
 struct Model {
     // Store the window ID so we can refer to this specific window later if needed.
@@ -22,17 +23,33 @@ struct Model {
     engine: PhysicsEngine,
 }
 
-fn fill_particles(_app: &App, colliders: &mut ColliderSet, bodies: &mut RigidBodySet) {
+fn random_vec(_app: &App) -> nalgebra::Vector2<f32> {
     let boundary = _app.window_rect();
+
+    let x = random_range(-100., 100.);
+    let y = random_range(-150., boundary.top());
+
+    vector![x, y]
+}
+
+fn fill_particles(app: &App, colliders: &mut ColliderSet, bodies: &mut RigidBodySet) {
+    let mut positions: Vec<nalgebra::Vector2<f32>> = Vec::new();
+
     for _ in 0..PARTICLE_COUNT {
-        let x = random_range(-100., 100.);
-        let y = random_range(-150., boundary.top());
+        let mut xy = random_vec(app);
+        while !positions
+            .iter()
+            .all(|pos| pos.metric_distance(&xy) > PARTICLE_SIZE * 2.)
+        {
+            xy = random_vec(app)
+        }
+        positions.push(xy);
 
         /* Create the bouncing ball. */
-        let rigid_body = RigidBodyBuilder::dynamic()
-            .translation(vector![x, y])
+        let rigid_body = RigidBodyBuilder::dynamic().translation(xy).build();
+        let collider = ColliderBuilder::ball(PARTICLE_SIZE)
+            .restitution(0.1)
             .build();
-        let collider = ColliderBuilder::ball(5.).restitution(0.1).build();
         let ball_body_handle = bodies.insert(rigid_body);
         colliders.insert_with_parent(collider, ball_body_handle, bodies);
     }