弧线运动 (Arc)
弧线运动
虽然对象是更逼真了，当它们遵循「缓入缓出」的时候它们很少沿直线运动——它们倾向于沿弧线运动。
我们有几种 CSS 的方式来实现弧线运动。一种是结合多个动画，比如在弹力球动画里，可以让球上下移动的同时让它右移，这时候球的显示效果就是沿弧线运动。
HTML
<h1>Principle 7: Arc (1)</h1>
<h2><a href="https://cssanimation.rocks/principles/" target="_parent">Animation Principles for the Web</h2>
<article class="principle sevena">
<div class="shape-container">
<div class="shape a"></div>
</div>
</article>
CSS
.sevena .shape-container {
animation: move-right 6s infinite cubic-bezier(.37,.55,.49,.67);
position: absolute;
left: calc(50% - 4em);
top: calc(50% - 4em);
}
.sevena .shape {
animation: bounce 6s infinite linear;
border-radius: 50%;
position: relative;
left: auto;
top: auto;
}
@keyframes move-right {
0% {
transform: translateX(-20em);
opacity: 1;
}
80% {
opacity: 1;
}
90%, 100% {
transform: translateX(20em);
opacity: 0;
}
}
@keyframes bounce {
0% {
transform: translateY(-8em);
animation-timing-function: cubic-bezier(.51,.01,.79,.02);
}
15% {
transform: translateY(8em);
animation-timing-function: cubic-bezier(.19,1,.7,1);
}
25% {
transform: translateY(-4em);
animation-timing-function: cubic-bezier(.51,.01,.79,.02);
}
32.5% {
transform: translateY(8em);
animation-timing-function: cubic-bezier(.19,1,.7,1);
}
40% {
transform: translateY(0em);
animation-timing-function: cubic-bezier(.51,.01,.79,.02);
}
45% {
transform: translateY(8em);
animation-timing-function: cubic-bezier(.19,1,.7,1);
}
50% {
transform: translateY(3em);
animation-timing-function: cubic-bezier(.51,.01,.79,.02);
}
56% {
transform: translateY(8em);
animation-timing-function: cubic-bezier(.19,1,.7,1);
}
60% {
transform: translateY(6em);
animation-timing-function: cubic-bezier(.51,.01,.79,.02);
}
64% {
transform: translateY(8em);
animation-timing-function: cubic-bezier(.19,1,.7,1);
}
66% {
transform: translateY(7.5em);
animation-timing-function: cubic-bezier(.51,.01,.79,.02);
}
70%, 100% {
transform: translateY(8em);
animation-timing-function: cubic-bezier(.19,1,.7,1);
}
}
/* General styling */
body {
margin: 0;
background: #e9b59f;
font-family: HelveticaNeue, Arial, Sans-serif;
color: #fff;
}
h1 {
position: absolute;
top: 0;
left: 0;
right: 0;
text-align: center;
font-weight: 300;
}
h2 {
font-size: 0.75em;
position: absolute;
bottom: 0;
left: 0;
right: 0;
text-align: center;
}
a {
text-decoration: none;
color: #333;
}
.principle {
width: 100%;
height: 100vh;
position: relative;
}
.shape {
background: #2d97db;
border: 1em solid #fff;
width: 4em;
height: 4em;
position: absolute;
top: calc(50% - 2em);
left: calc(50% - 2em);
}
另一种弧线运动
旋件运动
另外一种是旋转元件，我们可以设置一个在对象之外的原点来作为它的旋转中心。当我们旋转这个对象，它看上去就是沿着弧线运动。
HTML
<h1>Principle 7: Arc (2)</h1>
<h2><a href="https://cssanimation.rocks/principles/" target="_parent">Animation Principles for the Web</h2>
<article class="principle sevenb">
<div class="shape a"></div>
<div class="shape b"></div>
</article>
CSS
.sevenb .shape.a {
animation: sevenb 3s infinite linear;
top: calc(50% - 2em);
left: calc(50% - 9em);
transform-origin: 10em 50%;
}
.sevenb .shape.b {
animation: sevenb 6s infinite linear reverse;
background-color: yellow;
width: 2em;
height: 2em;
left: calc(50% - 1em);
top: calc(50% - 1em);
}
@keyframes sevenb {
100% {
transform: rotateZ(360deg);
}
}
/* General styling */
body {
margin: 0;
background: #e9b59f;
font-family: HelveticaNeue, Arial, Sans-serif;
color: #fff;
}
h1 {
position: absolute;
top: 0;
left: 0;
right: 0;
text-align: center;
font-weight: 300;
}
h2 {
font-size: 0.75em;
position: absolute;
bottom: 0;
left: 0;
right: 0;
text-align: center;
}
a {
text-decoration: none;
color: #333;
}
.principle {
width: 100%;
height: 100vh;
position: relative;
}
.shape {
background: #2d97db;
border: 1em solid #fff;
width: 4em;
height: 4em;
position: absolute;
top: calc(50% - 2em);
left: calc(50% - 2em);
}
—— END ——
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