canvas小球抛物线运动

2018-3-15 17:41| 作者: admin| 查看: 682| 评论: 0|来自: 蚂蚁部落

分享一段代码实例,它利用canvas实现了小球的抛射效果。

简单的抛物线效果,代码实例如下:

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<!DOCTYPE html>
<html>
<head>
<meta charset=" utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<title>蚂蚁部落</title>
<style>
html,body,canvas{
  width:100vw;
  height:100vh;
  background:#000000;
  overflow:hidden;
}
</style>
<script>
setTimeout(() => {
  let canvas = document.querySelector('canvas');
  let context = canvas.getContext('2d');
  canvas.width = canvas.offsetWidth;
  canvas.height = canvas.offsetHeight;

  let pointer = {
      x: 0,
      y: canvas.height / 2
  };

  let render =  () => {
    context.clearRect(0, 0, canvas.width, canvas.height);
    context.fillStyle = "green";
    context.beginPath();
    context.arc(pointer.x ,pointer.y, 100, 0, 2 * Math.PI, false);
    context.fill();
  };

  let vx = 7;
  let vy = -7;
  let run;
  ( run= () => {
    pointer.x += vx; // 位置恒定变化
    vy += 0.1; // 速度恒定变化
    pointer.y += vy;

    if (pointer.x > canvas.width 
       || pointer.y > canvas.height) {
      pointer.x = 0;
      pointer.y = canvas.height / 2;
      vy = -7;
    }
    render();
    requestAnimationFrame(run)
  })();
}, 500);
</script>
</head>
<body>
<canvas></canvas>
</body>
</html>



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