随机自然运动jquery

编辑: Raphael 显然更适合于此,因为它支持IE。jquery的问题是,由于CSS约束,圆角在IE中很难做到…在拉斐尔,交叉浏览的圈子里没有汗水。

jsFiddle with Raphael - all browsers :

(尽管看起来可能更好) speeded up in IE )

(function() {
    var paper, circs, i, nowX, nowY, timer, props = {}, toggler = 0, elie, dx, dy, rad, cur, opa;
    // Returns a random integer between min and max  
    // Using Math.round() will give you a non-uniform distribution!  
    function ran(min, max)  
    {  
        return Math.floor(Math.random() * (max - min + 1)) + min;  
    } 

    function moveIt()
    {
        for(i = 0; i < circs.length; ++i)
        {            
              // Reset when time is at zero
            if (! circs[i].time) 
            {
                circs[i].time  = ran(30, 100);
                circs[i].deg   = ran(-179, 180);
                circs[i].vel   = ran(1, 5);  
                circs[i].curve = ran(0, 1);
                circs[i].fade  = ran(0, 1);
                circs[i].grow  = ran(-2, 2); 
            }                
                // Get position
            nowX = circs[i].attr("cx");
            nowY = circs[i].attr("cy");   
               // Calc movement
            dx = circs[i].vel * Math.cos(circs[i].deg * Math.PI/180);
            dy = circs[i].vel * Math.sin(circs[i].deg * Math.PI/180);
                // Calc new position
            nowX += dx;
            nowY += dy;
                // Calc wrap around
            if (nowX < 0) nowX = 490 + nowX;
            else          nowX = nowX % 490;            
            if (nowY < 0) nowY = 490 + nowY;
            else          nowY = nowY % 490;

                // Render moved particle
            circs[i].attr({cx: nowX, cy: nowY});

                // Calc growth
            rad = circs[i].attr("r");
            if (circs[i].grow > 0) circs[i].attr("r", Math.min(30, rad +  .1));
            else                   circs[i].attr("r", Math.max(10,  rad -  .1));

                // Calc curve
            if (circs[i].curve > 0) circs[i].deg = circs[i].deg + 2;
            else                    circs[i].deg = circs[i].deg - 2;

                // Calc opacity
            opa = circs[i].attr("fill-opacity");
            if (circs[i].fade > 0) {
                circs[i].attr("fill-opacity", Math.max(.3, opa -  .01));
                circs[i].attr("stroke-opacity", Math.max(.3, opa -  .01)); }
            else {
                circs[i].attr("fill-opacity", Math.min(1, opa +  .01));
                circs[i].attr("stroke-opacity", Math.min(1, opa +  .01)); }

            // Progress timer for particle
            circs[i].time = circs[i].time - 1;

                // Calc damping
            if (circs[i].vel < 1) circs[i].time = 0;
            else circs[i].vel = circs[i].vel - .05;              

        } 
        timer = setTimeout(moveIt, 60);
    }

    window.onload = function () {
        paper = Raphael("canvas", 500, 500);
        circs = paper.set();
        for (i = 0; i < 30; ++i)
        {
            opa = ran(3,10)/10;
            circs.push(paper.circle(ran(0,500), ran(0,500), ran(10,30)).attr({"fill-opacity": opa,
                                                                           "stroke-opacity": opa}));
        }
        circs.attr({fill: "#00DDAA", stroke: "#00DDAA"});
        moveIt();
        elie = document.getElementById("toggle");
        elie.onclick = function() {
            (toggler++ % 2) ? (function(){
                    moveIt();
                    elie.value = " Stop ";
                }()) : (function(){
                    clearTimeout(timer);
                    elie.value = " Start ";
                }());
        }
    };
}());​

第一次尝试jquery解决方案如下:

这个jquery尝试在IE中失败很多,在FF中速度很慢。Chrome和Safari做得很好:

jsFiddle example for all browsers (IE is not that good)

(我没有执行淡入式IE,而且IE没有圆角…另外,JS速度较慢,因此总体上看起来相当糟糕)

jsFiddle example for Chrome and Safari only (4x more particles)

(function() {
    var x, y, $elie, pos, nowX, nowY, i, $that, vel, deg, fade, curve, ko, mo, oo, grow, len;

    // Returns a random integer between min and max  
    // Using Math.round() will give you a non-uniform distribution!  
    function ran(min, max)  
    {  
        return Math.floor(Math.random() * (max - min + 1)) + min;  
    } 

    function moveIt()
    {
        $("div.spec").each(function(i, v) {
            $elie = $(v);
            if (! $elie.data("time"))
            {
                $elie.data("time", ran(30, 100));
                $elie.data("deg", ran(-179, 180));
                $elie.data("vel", ran(3, 10));  
                $elie.data("curve", ran(0, 1));
                $elie.data("fade", ran(0, 1));
                $elie.data("grow", ran(-2, 2));                
            }

            vel = $elie.data("vel");
            deg = $elie.data("deg");
            fade = $elie.data("fade");            
            curve = $elie.data("curve");
            grow = $elie.data("grow");

            len = $elie.width();
            if (grow > 0)
                len = Math.min(len + grow, 50);
            else
                len = Math.max(len + grow, 20);

            $elie.css("-moz-border-radius", len/2);
            $elie.css("border-radius", len/2);

            $elie.css("width", len);
            $elie.css("height", len);

            pos = $elie.position();            

            $elie.data("time", $elie.data("time") - 1);

            if (curve)
                $elie.data("deg", (deg + 5) % 180);
            else
                $elie.data("deg", (deg - 5) % 180);

            ko = $elie.css("-khtml-opacity");
            mo = $elie.css("-moz-opacity");
            oo = $elie.css("opacity");
            if (fade)
            {
                $elie.css("-khtml-opacity", Math.max(ko - .1, .5));
                $elie.css("-moz-opacity", Math.max(mo - .1, .5));
                $elie.css("opacity", Math.max(oo - .1, .5));
            } else
            {
                $elie.css("-khtml-opacity", Math.min(ko - -.1, 1));
                $elie.css("-moz-opacity", Math.min(mo - -.1, 1));
                $elie.css("opacity", Math.min(oo - -.1, 1));                
            }

            if (vel < 3)
                $elie.data("time", 0);
            else
                $elie.data("vel", vel - .2);            


            nowX = pos.left;
            nowY = pos.top;

            x = vel * Math.cos(deg * Math.PI/180);
            y = vel * Math.sin(deg * Math.PI/180);

            nowX = nowX + x;            
            nowY = nowY + y;

            if (nowX < 0)
                nowX = 490 + nowX;
            else
                nowX = nowX % 490;

            if (nowY < 0)
                nowY = 490 + nowY;
            else
                nowY = nowY % 490;            
            $elie.css("left", nowX);
            $elie.css("top",  nowY);
        });
    }
    $(function() {
        $(document.createElement('div')).appendTo('body').attr('id', 'box');
        $elie = $("<div/>").attr("class","spec");
        // Note that math random is inclussive for 0 and exclussive for Max
        for (i = 0; i < 100; ++i)
        {
            $that = $elie.clone();  
            $that.css("top", ran(0, 495));
            $that.css("left", ran(0, 495));            
            $("#box").append($that);            
        }          
        timer = setInterval(moveIt, 60);
        $("input").toggle(function() {
            clearInterval(timer);
            this.value = " Start ";
        }, function() {
            timer = setInterval(moveIt, 60);        
            this.value = " Stop ";            
        });        
    });
}());
​

[部分答案,仅针对物理。]

[我刚才看到了前面的答案,我的答案有点类似。]

你可以试着模拟一些布朗运动,即 来自随机力和粘性阻尼的组合。Pseudocode:

initialize:
    x = random_position();
    v_x = random_velocity();  // v_x = velocity along x
    // and same for y
for (each time step) {
    x += v_x;
    v_x += random_force() - time_step / damping_time * v_x;
    // and same for y
}

保持阻尼时间长(~1秒),随机力振幅小。否则,运动可能会过于剧烈。

为了实现一个简单的高斯随机数生成器,请在维基百科中查找Box Muller。

根据数学原理,你给每个物体一个起始位置和速度。“随机行走”是通过计算受一定数量限制的随机角度来实现的(实验)。然后用这个角度改变速度矢量的角度。你也可以计算一个随机的速度增量,然后改变这个数量的向量的大小。因为你使用的是速度,所以运动会比较平稳。一种更先进的直接利用加速度计算速度和位置的方法。

对于随机转向值,二项分布优于均匀分布。二项分布集中在0附近,而不是均匀分布。您只需执行random()-random()(psuedocode)

矢量数学有广泛的文档记录,但如果遇到障碍,请留下评论。

我这边的回答很晚,但我想我可能会给出一个方法…

我个人会使用SVG矢量图像。 创建一个jquery插件,它接受不透明度和大小。使它们随机移动。 然后在创建一组这些粒子时执行javascript循环(不透明度和大小是随机的,加上起始位置是随机的) 然后让jquery插件在卸载粒子时启动自身的新实例。

(如果你看这部小电影,你会发现它们向一个方向移动,然后淡出,然后另一部淡入。)

不透明度效果将提供深度透视。

不确定我的回答是否有帮助,但我会朝那个方向走。