Canvas绘制粒子连线特效背景
var canvas = document.getElementById("cas"); var ctx = canvas.getContext("2d"); resize(); window.onresize = resize;
//定义画布大小的函数 function resize() { canvas.width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth; canvas.height = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight; }
//定时设置 浏览器下次重绘之前继续更新下一帧动画 var RAF = (function() { return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(callback) { window.setTimeout(callback, 1000 / 60); }; })(); // 鼠标活动时，获取鼠标坐标 var warea = {x: null, y: null, max: 20000}; window.onmousemove = function(e) { e = e || window.event; warea.x = e.clientX; warea.y = e.clientY; }; window.onmouseout = function(e) { warea.x = null; warea.y = null; }; // 添加粒子 // x，y为粒子坐标，xa, ya为粒子xy轴加速度，max为连线的最大距离 var dots = []; for (var i = 0; i < 300; i++) { var x = Math.random() * canvas.width; var y = Math.random() * canvas.height; var xa = Math.random() * 2 - 1; var ya = Math.random() * 2 - 1; dots.push({ x: x, y: y, xa: xa, ya: ya, max: 6000 }) } // 延迟100秒开始执行动画，如果立即执行有时位置计算会出错 setTimeout(function() { animate(); }, 100); // 每一帧循环的逻辑 function animate() { ctx.clearRect(0, 0, canvas.width, canvas.height); // 将鼠标坐标添加进去，产生一个用于比对距离的点数组 var ndots = [warea].concat(dots); dots.forEach(function(dot) { // 粒子位移 dot.x += dot.xa; dot.y += dot.ya; // 遇到边界将加速度反向 dot.xa *= (dot.x > canvas.width || dot.x < 0) ? -1 : 1; dot.ya *= (dot.y > canvas.height || dot.y < 0) ? -1 : 1; // 绘制点 ctx.fillRect(dot.x - 0.5, dot.y - 0.5, 1, 1); // 循环比对粒子间的距离 for (var i = 0; i < ndots.length; i++) { var d2 = ndots[i]; if (dot === d2 || d2.x === null || d2.y === null) continue; var xc = dot.x - d2.x; var yc = dot.y - d2.y; // 两个粒子之间的距离 var dis = xc * xc + yc * yc; // 距离比 var ratio; // 如果两个粒子之间的距离小于粒子对象的max值，则在两个粒子间画线 if (dis < d2.max) { // 如果是鼠标，则让粒子向鼠标的位置移动 if (d2 === warea && dis > (d2.max / 2)) { dot.x -= xc * 0.03; dot.y -= yc * 0.03; } // 计算距离比 ratio = (d2.max - dis) / d2.max; // 画线 ctx.beginPath(); ctx.lineWidth = ratio / 2; //线条颜色 ctx.strokeStyle = 'rgba(0,0,0,' + (ratio + 0.2) + ')'; ctx.moveTo(dot.x, dot.y); ctx.lineTo(d2.x, d2.y); ctx.stroke(); } } // 将已经计算过的粒子从数组中删除 ndots.splice(ndots.indexOf(dot), 1); }); RAF(animate); }
页面代码
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width,initial-scale=1.0,maximum-scale=1.0,minimum-scale=1.0,user-scalable=no"> <title></title> </head> <body> <!-- 页面背景 --> <canvas id="cas"></canvas> </body> <script src="https://ajax.aspnetcdn.com/ajax/jquery/jquery-3.5.1.min.js"></script> <script src="./js/canvas.js"></script> </html>
