90 lines
3.6 KiB
Markdown
90 lines
3.6 KiB
Markdown
|
---
|
|||
|
id: 587d78a9367417b2b2512ae8
|
|||
|
title: Learn How Bezier Curves Work
|
|||
|
challengeType: 0
|
|||
|
videoUrl: ''
|
|||
|
localeTitle: 了解Bezier曲线的工作原理
|
|||
|
---
|
|||
|
|
|||
|
## Description
|
|||
|
<section id="description">最后一项挑战引入了<code>animation-timing-function</code>属性和一些在其持续时间内改变动画速度的关键字。 CSS提供了除关键字之外的选项,通过使用贝塞尔曲线,可以更好地控制动画的播放方式。在CSS动画中,贝塞尔曲线与<code>cubic-bezier</code>函数一起使用。曲线的形状表示动画的播放方式。曲线位于1乘1坐标系上。此坐标系的X轴是动画的持续时间(将其视为时间刻度),Y轴是动画中的变化。 <code>cubic-bezier</code>函数由四个主要点组成,这些点位于1 x 1网格上: <code>p0</code> , <code>p1</code> , <code>p2</code>和<code>p3</code> 。为您设置<code>p0</code>和<code>p3</code> - 它们是始终分别位于原点(0,0)和(1,1)的起点和终点。您可以为其他两个点设置x和y值,并将它们放置在网格中的位置决定了要遵循的动画曲线的形状。这是在CSS中通过以下形式声明<code>p1</code>和<code>p2</code> “锚”点的x和y值来完成的: <code>(x1, y1, x2, y2)</code> 。将它们全部拉到一起,这里是CSS代码中Bezier曲线的一个例子: <code>animation-timing-function: cubic-bezier(0.25, 0.25, 0.75, 0.75);</code>在上面的示例中,x和y值对于每个点都是等效的(x1 = 0.25 = y1和x2 = 0.75 = y2),如果您记得几何类,则会产生从原点延伸到点的线(1 ,1)。此动画是动画长度期间元素的线性变化,与使用<code>linear</code>关键字相同。换句话说,它以恒定的速度变化。 </section>
|
|||
|
|
|||
|
## Instructions
|
|||
|
<section id="instructions">对于id为<code>ball1</code>的元素,将<code>animation-timing-function</code>属性的值从<code>linear</code>更改为其等效的<code>cubic-bezier</code>函数值。使用上面示例中给出的点值。 </section>
|
|||
|
|
|||
|
## Tests
|
|||
|
<section id='tests'>
|
|||
|
|
|||
|
```yml
|
|||
|
tests:
|
|||
|
- text: 具有id <code>ball1</code>的元素的<code>animation-timing-function</code>属性的值应该是线性等效的cubic-bezier函数。
|
|||
|
testString: 'assert($("#ball1").css("animation-timing-function") == "cubic-bezier(0.25, 0.25, 0.75, 0.75)", "The value of the <code>animation-timing-function</code> property for the element with the id <code>ball1</code> should be the linear-equivalent cubic-bezier function.");'
|
|||
|
- text: 具有id <code>ball2</code>的元素的<code>animation-timing-function</code>属性的<code>ball2</code>不应更改。
|
|||
|
testString: 'assert($("#ball2").css("animation-timing-function") == "ease-out", "The value of the <code>animation-timing-function</code> property for the element with the id <code>ball2</code> should not change.");'
|
|||
|
|
|||
|
```
|
|||
|
|
|||
|
</section>
|
|||
|
|
|||
|
## Challenge Seed
|
|||
|
<section id='challengeSeed'>
|
|||
|
|
|||
|
<div id='html-seed'>
|
|||
|
|
|||
|
```html
|
|||
|
<style>
|
|||
|
|
|||
|
.balls{
|
|||
|
border-radius: 50%;
|
|||
|
background: linear-gradient(
|
|||
|
35deg,
|
|||
|
#ccffff,
|
|||
|
#ffcccc
|
|||
|
);
|
|||
|
position: fixed;
|
|||
|
width: 50px;
|
|||
|
height: 50px;
|
|||
|
margin-top: 50px;
|
|||
|
animation-name: bounce;
|
|||
|
animation-duration: 2s;
|
|||
|
animation-iteration-count: infinite;
|
|||
|
}
|
|||
|
#ball1 {
|
|||
|
left: 27%;
|
|||
|
animation-timing-function: linear;
|
|||
|
}
|
|||
|
#ball2 {
|
|||
|
left: 56%;
|
|||
|
animation-timing-function: ease-out;
|
|||
|
}
|
|||
|
|
|||
|
@keyframes bounce {
|
|||
|
0% {
|
|||
|
top: 0px;
|
|||
|
}
|
|||
|
100% {
|
|||
|
top: 249px;
|
|||
|
}
|
|||
|
}
|
|||
|
|
|||
|
</style>
|
|||
|
|
|||
|
<div class="balls" id="ball1"></div>
|
|||
|
<div class="balls" id="ball2"></div>
|
|||
|
|
|||
|
```
|
|||
|
|
|||
|
</div>
|
|||
|
|
|||
|
|
|||
|
|
|||
|
</section>
|
|||
|
|
|||
|
## Solution
|
|||
|
<section id='solution'>
|
|||
|
|
|||
|
```js
|
|||
|
// solution required
|
|||
|
```
|
|||
|
</section>
|