[js高手之路]html5 canvas动画教程 - 重力、摩擦力、加速、抛物线运动 - JavaScript

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上节，我们讲了匀速运动，本节分享的运动就更有意思了：

加速运动
重力加速度
抛物线运动
摩擦力

加速运动:

<head>
<meta charset='utf-8' />
<style>
#canvas {
border: 1px dashed #aaa;
}
</style>
<script src="./ball.js"></script>
<script>
window.onload = function () {
var oCanvas = document.querySelector("#canvas"),
oGc = oCanvas.getContext('2d'),
width = oCanvas.width, height = oCanvas.height,
ball = new Ball( 0, height / 2 ),
vx = 0,
ax = 0.1;
(function linear() {
oGc.clearRect(0, 0, width, height);
ball.fill( oGc );
ball.x += vx;
vx += ax;
requestAnimationFrame(linear);
})();
}
</script>
</head>
<body>
<canvas id="canvas" width="1200" height="600"></canvas>
</body>

加速度分解与合成

<head>
<meta charset='utf-8' />
<style>
#canvas {
border: 1px dashed #aaa;
}
</style>
<script src="./ball.js"></script>
<script>
window.onload = function () {
var oCanvas = document.querySelector("#canvas"),
oGc = oCanvas.getContext('2d'),
width = oCanvas.width, height = oCanvas.height,
ball = new Ball( 0, 0 ),
a = 0.3,
ax = a * Math.cos( 25 * Math.PI / 180 ),
ay = a * Math.sin( 25 * Math.PI / 180 ),
vx = 0,
vy = 0;
(function linear() {
oGc.clearRect(0, 0, width, height);
ball.fill( oGc );
ball.x += vx;
ball.y += vy;
vx += ax;
vy += ay;
requestAnimationFrame(linear);
})();
}
</script>
</head>
<body>
<canvas id="canvas" width="1200" height="600"></canvas>
</body>

抛物线运动：

<head>
<meta charset='utf-8' />
<style>
#canvas {
border: 1px dashed #aaa;
}
</style>
<script src="./ball.js"></script>
<script>
window.onload = function () {
var oCanvas = document.querySelector("#canvas"),
oGc = oCanvas.getContext('2d'),
width = oCanvas.width, height = oCanvas.height,
ball = new Ball( 0, height / 2 ),
vy = -10,
vx = 5,
gravity = 0.2;
(function linear() {
oGc.clearRect(0, 0, width, height);
ball.fill( oGc );
ball.y += vy;
ball.x += vx;
vy += gravity;
requestAnimationFrame(linear);
})();
}
</script>
</head>
<body>
<canvas id="canvas" width="1200" height="600"></canvas>
</body>

重力弹跳:

<head>
<meta charset='utf-8' />
<style>
#canvas {
border: 1px dashed #aaa;
}
</style>
<script src="./ball.js"></script>
<script>
window.onload = function () {
var oCanvas = document.querySelector("#canvas"),
oGc = oCanvas.getContext('2d'),
width = oCanvas.width, height = oCanvas.height,
ball = new Ball( width / 2, 20 ),
vy = 0,
gravity = 0.2,
bounce = -0.6;
(function linear() {
oGc.clearRect(0, 0, width, height);
ball.fill( oGc );
ball.y += vy;
if ( ball.y > canvas.height - ball.radius ) {
ball.y = canvas.height - ball.radius;
vy *= bounce;
}
vy += gravity;
requestAnimationFrame(linear);
})();
}
</script>
</head>
<body>
<canvas id="canvas" width="1200" height="600"></canvas>
</body>

抛物线与重力弹跳运动

<head>
<meta charset='utf-8' />
<style>
#canvas {
border: 1px dashed #aaa;
}
</style>
<script src="./ball.js"></script>
<script>
window.onload = function () {
var oCanvas = document.querySelector("#canvas"),
oGc = oCanvas.getContext('2d'),
width = oCanvas.width, height = oCanvas.height,
ball = new Ball( 0, height ),
vy = -10,
vx = 5,
gravity = 0.2,
bounce = -0.8;
(function linear() {
oGc.clearRect(0, 0, width, height);
ball.fill( oGc );
ball.y += vy;
ball.x += vx;
if ( ball.y > canvas.height - ball.radius ) {
ball.y = canvas.height - ball.radius;
vy *= bounce;
}
vy += gravity;
requestAnimationFrame(linear);
})();
}
</script>
</head>
<body>
<canvas id="canvas" width="1200" height="600"></canvas>
</body>

摩擦力运动

<head>
<meta charset='utf-8' />
<style>
#canvas {
border: 1px dashed #aaa;
}
</style>
<script src="./ball.js"></script>
<script>
window.onload = function () {
var oCanvas = document.querySelector("#canvas"),
oGc = oCanvas.getContext('2d'),
width = oCanvas.width, height = oCanvas.height,
ball = new Ball( 0, height - 20 ),
vx = 20,
friction = 0.98;
(function linear() {
oGc.clearRect(0, 0, width, height);
ball.fill( oGc );
ball.x += vx;
vx *= friction;
requestAnimationFrame(linear);
})();
}
</script>
</head>
<body>
<canvas id="canvas" width="1200" height="600"></canvas>
</body>