1 files changed, 96 insertions, 0 deletions
diff --git a/random-attractors/js/main.js b/random-attractors/js/main.js
new file mode 100644
index 0000000..5355c6e
--- /dev/null
+++ b/random-attractors/js/main.js
@@ -0,0 +1,96 @@
+NUM_ATTRACTORS = 10;
+const canvas = document.getElementById("canvas");
+const ctx = canvas.getContext("2d");
+const { innerWidth, innerHeight } = window;
+const { random, floor, cos, sin } = Math;
+canvas.width = innerWidth;
+canvas.height = innerHeight;
+const w = innerWidth / 2;
+const h = innerHeight / 2;
+
+ctx.translate(w, h);
+ctx.globalCompositeOperation = "lighter";
+const range = n =>
+  Array(n)
+    .fill(0)
+    .map((_, i) => i);
+const randomInt = (s, e) => s + floor((e - s) * random());
+const drawParticle = ({ x, y, c }) => {
+  ctx.beginPath();
+  ctx.fillStyle = c;
+  ctx.fillRect(x, y, 0.5, 0.5);
+  ctx.closePath();
+};
+
+const attractors = range(NUM_ATTRACTORS).map(() => ({
+  x: randomInt(-w, w),
+  y: randomInt(-h, h),
+  g: randomInt(0, 30),
+  c: `rgba(${randomInt(0, 255)}, ${randomInt(0, 255)}, ${randomInt(
+    0,
+    255
+  )}, ${random()})`
+}));
+
+// https://codepen.io/ge1doot/pen/ooNvgx
+class Particle {
+  constructor() {
+    this.damp = 0.00006;
+    this.accel = 3200;
+    this.x = randomInt(-w, w);
+    this.y = randomInt(-h, h);
+    this.vx = this.accel * random();
+    this.vy = this.accel * random();
+    this.currentColor = "#fff";
+  }
+  draw() {
+    const { x, y, currentColor } = this;
+    drawParticle({ x, y, c: currentColor });
+  }
+  step() {
+    const { x, y } = this;
+
+    let color = 0;
+    let largestVal = 0;
+
+    attractors.map(a => {
+      const dx = a.x - x;
+      const dy = a.y - y;
+      const d2 = (dx * dx + dy * dy) / a.g;
+      if (d2 > 0.1) {
+        this.vx += this.accel * (dx / d2);
+        this.vy += this.accel * (dy / d2);
+      }
+      if (d2 > largestVal) {
+        largestVal = d2;
+        color = a.c;
+      }
+    });
+    this.x += this.vx;
+    this.y += this.vy;
+
+    this.vx *= this.damp;
+    this.vy *= this.damp;
+
+    this.currentColor = color;
+    this.draw();
+  }
+}
+
+const particles = range(8000).map(() => new Particle());
+const animate = () => {
+  particles.map(particle => {
+    particle.step();
+  });
+};
+
+let iter = 0;
+
+const update = () => {
+  animate();
+  iter += 1;
+  if (iter < 1500) {
+    requestAnimationFrame(update);
+  }
+};
+update();