Added Simple Physics Simulation (Confetti)

A super simple 2D simulation where balls fall and bounce off each other.
Click to spawn new balls.

examples/confetti

@@ -0,0 +1,146 @@
+use std::u8;
+use macroquad::prelude::*;
+
+#[derive(Debug, Clone, Copy)]
+pub struct Ball {
+    id: usize,
+    x: f32,
+    y: f32,
+    x_vel: f32,
+    y_vel: f32,
+    color: Color,
+}
+
+// Customizable
+const FLOOR_LOSS: f32 = 0.98;
+const DRAG: f32 = 0.998;
+const GRAVITY: f32 = 1.0;
+
+const BALL_RADIUS: f32 = 6.0;
+
+// Please, don't change
+static mut BALL_ID : usize = 0;
+const BALL_RADIUS_SQR: f32= BALL_RADIUS * BALL_RADIUS;
+
+impl Ball {
+    fn new(x: f32, y:f32, seed:usize) -> Ball{   
+        let id;
+        unsafe {
+            id = BALL_ID;
+            BALL_ID += 1;
+        }
+
+        let seed = seed % (usize::MAX/64);
+        let random = (32_1239 * seed*seed*seed* 17 + id)% 1000 ;
+        let x_vel = random % 9;
+        let x_vel =  (x_vel as f32 - 4.0) / 2.0;
+
+        return Ball{id, x, y, x_vel, y_vel:0.0, color:Color::from_rgba((random as usize*47%255) as u8, (random as usize*29%255) as u8, (random as usize*101%255) as u8, u8::MAX)}
+    }
+
+    fn tick(&mut self){
+        self.x_vel *= DRAG;
+        self.y_vel *= DRAG;
+
+        self.x += self.x_vel;
+        self.y += self.y_vel;
+
+        if self.y > screen_height(){
+            // self.y = screen_height();
+            self.y_vel = -self.y_vel * FLOOR_LOSS;
+        }else{
+            self.y_vel += GRAVITY;
+        }
+
+        if self.x < 0.0 || self.x > screen_width(){
+            self.x_vel = -self.x_vel * FLOOR_LOSS;
+        }
+    }
+
+    fn draw(&self){
+        draw_circle(self.x, self.y-BALL_RADIUS, BALL_RADIUS, self.color);
+    }
+
+    fn collide(&mut self, balls: &[Ball]) {
+        for other in balls {
+            if other.id == self.id {
+                continue; 
+            }
+
+            let dx = self.x - other.x;
+            let dy = self.y - other.y;
+            let distance_sqr = dx * dx + dy * dy;
+
+            if distance_sqr > BALL_RADIUS_SQR {
+                continue; 
+            }
+
+            let distance = distance_sqr.sqrt();
+            if distance == 0.0 {
+                continue;
+            }
+            let nx = dx / distance; 
+            let ny = dy / distance; 
+
+            let relative_velocity_x = self.x_vel - other.x_vel;
+            let relative_velocity_y = self.y_vel - other.y_vel;
+            let relative_velocity_normal = relative_velocity_x * nx + relative_velocity_y * ny;
+
+            if relative_velocity_normal > 0.0 {
+                continue;
+            }
+
+            let impulse = (2.0 * relative_velocity_normal) / 2.0 * FLOOR_LOSS;
+
+            self.x_vel -= impulse * nx;
+            self.y_vel -= impulse * ny;
+        }
+    }
+
+}
+
+#[macroquad::main("AM - Confetti")]
+async fn main() {
+
+    let mut balls: Vec<Ball> = Vec::new();
+    let mut frame_count: usize = 0;
+    loop {
+        // Loop start
+        frame_count += 1;
+        clear_background(Color { r: 0.95, g: 0.9, b: 0.9, a: 1.0 });
+
+        // Handle Inputs
+        if is_mouse_button_down(MouseButton::Left) || is_mouse_button_pressed(MouseButton::Right) {
+            let (mouse_x,mouse_y) = mouse_position();
+            balls.push(Ball::new(mouse_x, mouse_y ,frame_count))
+        }
+
+        if is_key_pressed(KeyCode::Space) {
+            unsafe {
+                BALL_ID = 0;
+                balls.clear();
+            }
+        }
+
+        // Handle Tick
+        let balls_prev = balls.to_vec();        
+        for ball in &mut balls {
+            ball.collide(&balls_prev);
+            ball.tick();
+            ball.draw();
+        }   
+
+        unsafe {
+            if BALL_ID == 0 {
+                draw_text("Click anywhere to begin!", screen_width()/2.0 - 240.0, screen_height()/2.0, 48.0, RED);
+            }else{
+                draw_text(&format!("Balls{}: {}", if BALL_ID > 999 {" (Press Space to Reset)"} else {""}, BALL_ID), 15.0, 25.0, 32.0, BLACK);
+            }            
+        }
+
+        next_frame().await
+    }
+}
+
+// Andrew McCall <3
+// https://github.com/Andrew-McCall/MacroquadConfetti