HTML Canvas Animation Spring with ball chain

Description

HTML Canvas Animation Spring with ball chain

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<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Chain</title>
  </head>//from ww  w  . j  ava2  s .  c o m
  <body>
    <canvas id="canvas" width="400" height="400"></canvas>
    <aside>Move mouse on canvas element.</aside>
    <script>
class Ball {
  constructor() {
    this.x = 0;
    this.y = 0;
    this.radius = 4;
    this.vx = 0;
    this.vy = 0;
    this.rotation = 0;
    this.scaleX = 1;
    this.scaleY = 1;
    this.color = 'blue';
    this.lineWidth = 1;
  }

  draw(context) {
    context.save();
    context.translate(this.x, this.y);
    context.rotate(this.rotation);
    context.scale(this.scaleX, this.scaleY);
    
    context.lineWidth = this.lineWidth;
    context.fillStyle = this.color;
    context.beginPath();
    //x, y, radius, start_angle, end_angle, anti-clockwise
    context.arc(0, 0, this.radius, 0, Math.PI * 2, true);
    context.closePath();
    context.fill();
    if (this.lineWidth > 0) {
      context.stroke();
    }
    context.restore();
  }

  getBounds() {
    return {
      x: this.x - this.radius,
      y: this.y - this.radius,
      width: this.radius * 2,
      height: this.radius * 2
    };
  }
}
captureMouse = function (element) {
  var mouse = {x: 0, y: 0, event: null},
      body_scrollLeft = document.body.scrollLeft,
      element_scrollLeft = document.documentElement.scrollLeft,
      body_scrollTop = document.body.scrollTop,
      element_scrollTop = document.documentElement.scrollTop,
      offsetLeft = element.offsetLeft,
      offsetTop = element.offsetTop;
  
  element.addEventListener('mousemove', function (event) {
    var x, y;
    
    if (event.pageX || event.pageY) {
      x = event.pageX;
      y = event.pageY;
    } else {
      x = event.clientX + body_scrollLeft + element_scrollLeft;
      y = event.clientY + body_scrollTop + element_scrollTop;
    }
    x -= offsetLeft;
    y -= offsetTop;
    
    mouse.x = x;
    mouse.y = y;
    mouse.event = event;
  }, false);
  
  return mouse;
};     
    window.onload = function () {
      var canvas = document.getElementById('canvas'),
          context = canvas.getContext('2d'),
          mouse = captureMouse(canvas),
          ball0 = new Ball(),
          ball1 = new Ball(),
          ball2 = new Ball(),
          spring = 0.03,
          friction = 0.9,
          gravity = 2;

      function move (ball, targetX, targetY) {
        ball.vx += (targetX - ball.x) * spring;
        ball.vy += (targetY - ball.y) * spring;
        ball.vy += gravity;
        ball.vx *= friction;
        ball.vy *= friction;
        ball.x += ball.vx;
        ball.y += ball.vy;
      }

      (function drawFrame () {
        window.requestAnimationFrame(drawFrame, canvas);
        context.clearRect(0, 0, canvas.width, canvas.height);

        move(ball0, mouse.x, mouse.y);
        move(ball1, ball0.x, ball0.y);
        move(ball2, ball1.x, ball1.y);

        //draw spring
        context.beginPath();
        context.moveTo(mouse.x, mouse.y);
        context.lineTo(ball0.x, ball0.y);
        context.lineTo(ball1.x, ball1.y);
        context.lineTo(ball2.x, ball2.y);
        context.stroke();

        //draw balls
        ball0.draw(context);
        ball1.draw(context);
        ball2.draw(context);
      }());
    };
    </script>
  </body>
</html>



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