个人CSS技能查漏补缺系列

关键在于使用关键帧(keyframs)时让两个动画重叠，并让其中一个动画延迟

直接上代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #wrapper {
            --ballCount: 2; /* 小球数量 */
            --ballAnimTime: 1s; /* 动画单轮总时间 */
            --ballAnimDeley: calc(var(--ballAnimTime) / 4); /* 为了实现椭圆轨迹而计算的延迟时间，为单轮总时间除以4 */
            --ballUnitAnimTime: calc(var(--ballAnimTime) / var(--ballCount)); /* 小球延迟，为单轮总时间除以小球数量 */

            position: relative;
            width: 60vw;
            height: 30vw;
            border: 1px solid black;
            overflow: hidden;
            resize: auto;
        }

        #wrapper > .ball {
            position: absolute;
            transform: translate(-50%, -50%);
            width: 2vw;
            height: 2vw;
            border-radius: 50%;
            background-color: blue;
        }

        /* Y轴移动动画 */
        @keyframes moveY {
            from {
                top: 0;
            }
            to {
                top: 100%;
            }
        }
        /* X轴移动动画 */
        @keyframes moveX {
            from {
                left: 0;
            }
            to {
                left: 100%;
            }
        }

        #wrapper > .ball1 {
            /* moveY需要比moveX延迟一段时间，才能显示出椭圆轨迹，这个时间为--ballAnimDeley*/
            /* animation: name duration timing-function delay iteration-count direction fill-mode; */
            animation: 
            moveY calc(var(--ballAnimTime) / 2) cubic-bezier(0.6, 0.3, 0.3, 0.6) calc(-1 * (var(--ballAnimDeley) + 0 * var(--ballUnitAnimTime))) infinite alternate,
            moveX calc(var(--ballAnimTime) / 2) cubic-bezier(0.6, 0.3, 0.3, 0.6) calc(-1 * 0 * var(--ballUnitAnimTime)) infinite alternate;
        }

        #wrapper > .ball2 {
            animation: 
            moveY calc(var(--ballAnimTime) / 2) cubic-bezier(0.6, 0.3, 0.3, 0.6) calc(-1 * (var(--ballAnimDeley) + 1 * var(--ballUnitAnimTime))) infinite alternate,
            moveX calc(var(--ballAnimTime) / 2) cubic-bezier(0.6, 0.3, 0.3, 0.6) calc(-1 * 1 * var(--ballUnitAnimTime)) infinite alternate;
        }
    </style>
</head>
<body>
    <p>线框右下角可以拖拽改变大小</p>
    <div id="wrapper">
        <div class="ball ball1"></div>
        <div class="ball ball2"></div>
    </div>
</body>
</html>

<!-- more -->

参考https://www.cnblogs.com/lin494910940/p/14051631.html

用Javascript实现

后来发现css实现的效果不好，小球运动到盒子四边时会有明显的碰撞感，所以这里用js实现一下

目录结构

EllipsisGenerator.js
index.html

// EllipsisGenerator.js

/**
 * 椭圆轨道坐标生成器类
 */
class EllipsisGenerator {
    x;
    y;
    a;
    b;
    angle;
    angleStep;

    /**
     * 构造一个椭圆轨道
     * @param {Number} x 圆心x坐标
     * @param {Number} y 圆心y坐标
     * @param {Number} a x轴半径长度
     * @param {Number} b y轴半径长度
     * @param {Number} angle 起始角度 单位deg
     * @param {Number} angleStep 角度自增值 单位deg
     */
    constructor(x, y, a, b, angle = 0, angleStep = 1) {
        this.x = x;
        this.y = y;
        this.a = a;
        this.b = b;
        this.angle = angle;
        this.angleStep = angleStep;
    }

    /**
     * *generate方法返回一个迭代器，每次调用迭代器的next方法就会使角度(this.angle)自增(this.angleStep)，
     * 然后返回角度射线与椭圆轨道的交点坐标(x,y)，即椭圆轨道坐标
     */
    *generate() {
        while (true) {
            let radians = this.angle * Math.PI / 180
                , tx = this.a * Math.cos(radians)
                , ty = this.b * Math.sin(radians);

            yield {
                x: this.x + tx,
                y: this.y + ty
            }

            if (this.angle >= 360) {
                this.angle = 1;
            } else {
                this.angle += this.angleStep;
            }
        }
    }
}

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta http-equiv="X-UA-Compatible" content="IE=edge" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Document</title>
    </head>
    <body>
        <canvas id="container" style="border: 1px solid"></canvas>
        <script src="./EllipsisGenerator.js"></script>
        <script>
            const bubbleCount = 100; // 球球数量
            const bubbleRadius = 10; // 球球半径
            const frameRate = 40; // 渲染帧数；每秒40帧
            const bubbleColor = 'yellowgreen';
            const bubbles = [];
            class Bubble {
                x;
                y;
                r;
                alpha;
                constructor(x = 0, y = 0, r = 1, alpha = 1) {
                    this.x = x;
                    this.y = y;
                    this.r = r;
                    this.alpha = alpha;
                }
            }

            const $star = document.getElementById('container');
            const width = 600;
            const height = 400;
            $star.width = width;
            $star.height = height;

            const elliptic = new EllipsisGenerator(
                width / 2,
                height / 2,
                width / 2 - bubbleRadius,
                height / 2 - bubbleRadius,
                0,
                -1
            );
            const generate = elliptic.generate();

            const ctx = $star.getContext('2d');

            const run = () => {
                ctx.clearRect(0, 0, width, height);
                let { x, y } = generate.next().value;

                if (bubbles.length >= bubbleCount) {
                    bubbles.shift();
                }

                let bubble = new Bubble(x, y, 2);
                bubbles.push(bubble);

                //渲染bubble数组
                for (let i = 0; i < bubbles.length; i++) {
                    let bubble = bubbles[i];
                    bubble.alpha = (i + 1) * (1 / bubbleCount);
                    bubble.r = bubble.r * (i + 1) * (1 / bubbleCount);

                    ctx.save();
                    ctx.beginPath();
                    ctx.globalAlpha = bubble.alpha * 0.5;
                    ctx.fillStyle = bubbleColor;
                    ctx.arc(
                        bubble.x,
                        bubble.y,
                        bubble.r * 4,
                        0,
                        2 * Math.PI,
                        false
                    );
                    ctx.fill();
                    ctx.restore();
                }

                setTimeout(() => {
                    requestAnimationFrame(run);
                }, 1000 / frameRate);
            };

            run();
        </script>
    </body>
</html>

用CSS做一个椭圆轨道小球运动动画

用Javascript实现