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Wobbling Ball With Canvas

  1. // same as yesterday but with canvas instead of svg
  2. const canvas = document.createElement('canvas'),
  3.       c = canvas.getContext('2d');
  4. document.body.appendChild(canvas);
  5. document.body.style.margin = 0;
  6.  
  7. let w = window.innerWidth,
  8.     h = window.innerHeight,
  9.     x = w / 2,
  10.     y = h / 2,
  11.     vx = vy = dx = dy = 0,
  12.     damp = 0.99, div = 8, ticks = 0, 
  13.     wobbleChance = 0.03,
  14.     startTick = 50;
  15.  
  16. function loop() {
  17.  
  18.   w = window.innerWidth;
  19.   h = window.innerHeight;
  20.   radius = w * 0.05;
  21.   diam = radius * 2;
  22.   diam2x = diam * 2;
  23.  
  24.   if (x > w){
  25.     vx *= -1;
  26.     dx *= -1;
  27.     x = w;
  28.   } else if (x < 0){
  29.     vx *= -1;
  30.     dx *= -1;
  31.     x = 0;
  32.   }
  33.  
  34.   if (y > h) {
  35.     vy *= -1;
  36.     dy *= -1;
  37.     y = h;
  38.   } else if (y < 0) {
  39.     vy *= -1;
  40.     dy *= -1;
  41.     y = 0
  42.   } 
  43.  
  44.   if (
  45.     Math.random() < wobbleChance || 
  46.     ticks === startTick) {
  47.       dx += Math.random() * 10 - 5;
  48.       dy += Math.random() * 10 - 5;
  49.   }
  50.  
  51.   dx *= damp;
  52.   dy *= damp;
  53.  
  54.   vx += (dx - vx) / div;
  55.   vy += (dy - vy) / div;
  56.  
  57.   x += vx;
  58.   y += vy;
  59.  
  60.   // in most cases these days you
  61.   // just clear the whole canvas, but for
  62.   // this example we clear a rectangle around 
  63.   // the circle 
  64.   c.clearRect(
  65.     x - diam, 
  66.     y - diam, 
  67.     diam2x, 
  68.     diam2x
  69.   );
  70.  
  71.   // draw the path
  72.   c.fillStyle = 'red'
  73.   c.beginPath();
  74.   c.arc(x, y, radius, 0, Math.PI * 2, false);
  75.   c.fill();
  76.  
  77.   ticks++;
  78.   window.requestAnimationFrame(loop);
  79. }
  80. loop();
  81.  
  82. function resize() {
  83.   canvas.width = window.innerWidth;
  84.   canvas.height = window.innerHeight;
  85. }
  86. resize();
  87. window.addEventListener('resize', resize);

A wobbling ball with canvas.

snippet.zone ~ 2021-22 /// {s/z}