酷炫的粒子背景效果

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        酷炫粒子背景
        我们一起进步

// min and max radius, radius threshold and percentage of filled circles
var radMin = 5,
    radMax = 125,
    filledCircle = 60, //percentage of filled circles
    concentricCircle = 30, //percentage of concentric circles
    radThreshold = 25; //IFF special, over this radius concentric, otherwise filled

//min and max speed to move
var speedMin = 0.3,
    speedMax = 2.5;

//max reachable opacity for every circle and blur effect
var maxOpacity = 0.6;

//default palette choice
var colors = ['52,168,83', '117,95,147', '199,108,23', '194,62,55', '0,172,212', '120,120,120'],
    bgColors = ['52,168,83', '117,95,147', '199,108,23', '194,62,55', '0,172,212', '120,120,120'],
    circleBorder = 10,
    backgroundLine = bgColors[0];
var backgroundMlt = 0.85;

//min distance for links
var linkDist = Math.min(canvas.width, canvas.height) / 2.4,
    lineBorder = 2.5;

//most importantly: number of overall circles and arrays containing them
var maxCircles = 12,
    points = [],
    pointsBack = [];

//populating the screen
for (var i = 0; i < maxCircles * 2; i++) points.push(new Circle());
for (var i = 0; i < maxCircles; i++) pointsBack.push(new Circle(true));

//experimental vars
var circleExp = 1,
    circleExpMax = 1.003,
    circleExpMin = 0.997,
    circleExpSp = 0.00004,
    circlePulse = false;

//circle class
function Circle(background) {
    //if background, it has different rules
    this.background = (background || false);
    this.x = randRange(-canvas.width / 2, canvas.width / 2);
    this.y = randRange(-canvas.height / 2, canvas.height / 2);
    this.radius = background ? hyperRange(radMin, radMax) * backgroundMlt : hyperRange(radMin, radMax);
    this.filled = this.radius < radThreshold ? (randint(0, 100) > filledCircle ? false : 'full') : (randint(0, 100) > concentricCircle ? false : 'concentric');
    this.color = background ? bgColors[randint(0, bgColors.length - 1)] : colors[randint(0, colors.length - 1)];
    this.borderColor = background ? bgColors[randint(0, bgColors.length - 1)] : colors[randint(0, colors.length - 1)];
    this.opacity = 0.05;
    this.speed = (background ? randRange(speedMin, speedMax) / backgroundMlt : randRange(speedMin, speedMax)); // * (radMin / this.radius);
    this.speedAngle = Math.random() * 2 * Math.PI;
    this.speedx = Math.cos(this.speedAngle) * this.speed;
    this.speedy = Math.sin(this.speedAngle) * this.speed;
    var spacex = Math.abs((this.x - (this.speedx < 0 ? -1 : 1) * (canvas.width / 2 + this.radius)) / this.speedx),
        spacey = Math.abs((this.y - (this.speedy < 0 ? -1 : 1) * (canvas.height / 2 + this.radius)) / this.speedy);
    this.ttl = Math.min(spacex, spacey);
};

Circle.prototype.init = function() {
    Circle.call(this, this.background);
}

//support functions
//generate random int a<=x<=b
function randint(a, b) {
    return Math.floor(Math.random() * (b - a + 1) + a);
}
//generate random float
function randRange(a, b) {
    return Math.random() * (b - a) + a;
}
//generate random float more likely to be close to a
function hyperRange(a, b) {
    return Math.random() * Math.random() * Math.random() * (b - a) + a;
}

//rendering function
function drawCircle(ctx, circle) {
    //circle.radius *= circleExp;
    var radius = circle.background ? circle.radius *= circleExp : circle.radius /= circleExp;
    ctx.beginPath();
    ctx.arc(circle.x, circle.y, radius * circleExp, 0, 2 * Math.PI, false);
    ctx.lineWidth = Math.max(1, circleBorder * (radMin - circle.radius) / (radMin - radMax));
    ctx.strokeStyle = ['rgba(', circle.borderColor, ',', circle.opacity, ')'].join('');
    if (circle.filled == 'full') {
        ctx.fillStyle = ['rgba(', circle.borderColor, ',', circle.background ? circle.opacity * 0.8 : circle.opacity, ')'].join('');
        ctx.fill();
        ctx.lineWidth = 0;
        ctx.strokeStyle = ['rgba(', circle.borderColor, ',', 0, ')'].join('');
    }
    ctx.stroke();
    if (circle.filled == 'concentric') {
        ctx.beginPath();
        ctx.arc(circle.x, circle.y, radius / 2, 0, 2 * Math.PI, false);
        ctx.lineWidth = Math.max(1, circleBorder * (radMin - circle.radius) / (radMin - radMax));
        ctx.strokeStyle = ['rgba(', circle.color, ',', circle.opacity, ')'].join('');
        ctx.stroke();
    }
    circle.x += circle.speedx;
    circle.y += circle.speedy;
    if (circle.opacity < (circle.background ? maxOpacity : 1)) circle.opacity += 0.01;
    circle.ttl--;
}

//initializing function
function init() {
    window.requestAnimationFrame(draw);
}

//rendering function
function draw() {

if (circlePulse) {
        if (circleExp < circleExpMin || circleExp > circleExpMax) circleExpSp *= -1;
        circleExp += circleExpSp;
    }
    var ctxfr = document.getElementById('canvas').getContext('2d');
    var ctxbg = document.getElementById('canvasbg').getContext('2d');

ctxfr.globalCompositeOperation = 'destination-over';
    ctxfr.clearRect(0, 0, canvas.width, canvas.height); // clear canvas
    ctxbg.globalCompositeOperation = 'destination-over';
    ctxbg.clearRect(0, 0, canvas.width, canvas.height); // clear canvas

ctxfr.save();
    ctxfr.translate(canvas.width / 2, canvas.height / 2);
    ctxbg.save();
    ctxbg.translate(canvas.width / 2, canvas.height / 2);

//function to render each single circle, its connections and to manage its out of boundaries replacement
    function renderPoints(ctx, arr) {
        for (var i = 0; i < arr.length; i++) {
            var circle = arr[i];
            //checking if out of boundaries
            if (circle.ttl < 0) {}
            var xEscape = canvas.width / 2 + circle.radius,
                yEscape = canvas.height / 2 + circle.radius;
            if (circle.ttl < -20) arr[i].init(arr[i].background);
            //if (Math.abs(circle.y) > yEscape || Math.abs(circle.x) > xEscape) arr[i].init(arr[i].background);
            drawCircle(ctx, circle);
        }
        for (var i = 0; i < arr.length - 1; i++) {
            for (var j = i + 1; j < arr.length; j++) {
                var deltax = arr[i].x - arr[j].x;
                var deltay = arr[i].y - arr[j].y;
                var dist = Math.pow(Math.pow(deltax, 2) + Math.pow(deltay, 2), 0.5);
                //if the circles are overlapping, no laser connecting them
                if (dist <= arr[i].radius + arr[j].radius) continue;
                //otherwise we connect them only if the dist is < linkDist
                if (dist < linkDist) {
                    var xi = (arr[i].x < arr[j].x ? 1 : -1) * Math.abs(arr[i].radius * deltax / dist);
                    var yi = (arr[i].y < arr[j].y ? 1 : -1) * Math.abs(arr[i].radius * deltay / dist);
                    var xj = (arr[i].x < arr[j].x ? -1 : 1) * Math.abs(arr[j].radius * deltax / dist);
                    var yj = (arr[i].y < arr[j].y ? -1 : 1) * Math.abs(arr[j].radius * deltay / dist);
                    ctx.beginPath();
                    ctx.moveTo(arr[i].x + xi, arr[i].y + yi);
                    ctx.lineTo(arr[j].x + xj, arr[j].y + yj);
                    var samecolor = arr[i].color == arr[j].color;
                    ctx.strokeStyle = ["rgba(", arr[i].borderColor, ",", Math.min(arr[i].opacity, arr[j].opacity) * ((linkDist - dist) / linkDist), ")"].join("");
                    ctx.lineWidth = (arr[i].background ? lineBorder * backgroundMlt : lineBorder) * ((linkDist - dist) / linkDist); //*((linkDist-dist)/linkDist);
                    ctx.stroke();
                }
            }
        }
    }

var startTime = Date.now();
    renderPoints(ctxfr, points);
    renderPoints(ctxbg, pointsBack);
    deltaT = Date.now() - startTime;

ctxfr.restore();
    ctxbg.restore();

window.requestAnimationFrame(draw);
}

init();

↑上面代码改变，会自动显示代码结果

jQuery调用版本：2.1.4

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代码描述：canvas画的一款动态登陆背景，粒子背景。

动态的登陆页面背景。超酷炫。

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