JavaScript实现扯网动画效果的示例代码

更新时间：2022年06月23日 08:38:35 作者：肥学

这篇文章主要为大家详细介绍了如何利用JavaScript语言实现扯网动画效果，文中的示例代码讲解详细，对我们学习JS有一定的帮助，需要的可以参考一下

演示

技术栈

JavaScript prototype（原型对象）：所有的 JavaScript 对象都会从一个 prototype（原型对象）中继承属性和方法。Date 对象从 Date.prototype 继承。 Array 对象从 Array.prototype 继承。 Person 对象从 Person.prototype 继承。所有 JavaScript 中的对象都是位于原型链顶端的 Object 的实例。

JavaScript 对象有一个指向一个原型对象的链。当试图访问一个对象的属性时，它不仅仅在该对象上搜寻，还会搜寻该对象的原型，以及该对象的原型的原型，依次层层向上搜索，直到找到一个名字匹配的属性或到达原型链的末尾。

Date 对象, Array 对象, 以及 Person 对象从 Object.prototype 继承。

添加属性和方法有的时候我们想要在所有已经存在的对象添加新的属性或方法。

另外，有时候我们想要在对象的构造函数中添加属性或方法。例如：

function Person(first, last, age, eyecolor) {
  this.firstName = first;
  this.lastName = last;
  this.age = age;
  this.eyeColor = eyecolor;
}
 
Person.prototype.nationality = "English";

也可以这样：

function Person(first, last, age, eyecolor) {
  this.firstName = first;
  this.lastName = last;
  this.age = age;
  this.eyeColor = eyecolor;
}
 
Person.prototype.name = function() {
  return this.firstName + " " + this.lastName;
};

源码

css控制

* {
    margin: 0;
    overflow: hidden;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    -o-user-select: none;
    user-select: none;
}
body {
    background: #F2F2F2;
}
#c {
    display: block;
    margin: 20px auto 0;
}
#info {
    position: absolute;
    left: -1px;
    top: -1px;
    width: auto;
    max-width: 420px;
    height: auto;
    background: #f2f2f2;
    border-bottom-right-radius: 10px;
    border:1px solid #333;
}
#top {
    background: #fff;
    width: 100%;
    height: auto;
    position: relative;
    border-bottom: 1px solid #eee;
}
p {
    font-family: Arial, sans-serif;
    color: #666;
    text-align: justify;
    font-size: 16px;
    margin: 10px 16px;
}
#github {
  color:#3377ee;
  font-family: Helvetica, Arial, sans-serif;
  font-size: 19px;
  display: block;
  margin: 0 auto;
  text-align: center;
  text-decoration:none;
}
#net {
  text-align:center;
  white-space:nowrap;
  font-size:19px;
  background:rgba(0,0,0,0.1);
  padding:8px 12px;
  border-radius:8px;
  display:block;
  color:#888;
}
#net > span {
  color:#3377ee;
  font-family: Helvetica, Arial, sans-serif;
  font-size: 14px;
  display: block;
  margin: 0 auto;
  text-align: center;
  text-decoration:none;
}
a {
    font-family: sans-serif;
    color: #444;
    text-decoration: none;
    font-size: 20px;
}
#site {
    float: left;
    margin: 10px;
    color: #ff9900;
  border-bottom: 1px dashed #ccc;
  padding-bottom:3px
}
#site:hover {
    color: #ffaa11;
}
#close {
    float: right;
    margin: 10px;
}
#p {
    font-family: Verdana, sans-serif;
    position: absolute;
    right: 10px;
    bottom: 10px;
    color: #4099ff;
    border: 1px dashed #4099ff;
    padding: 4px 8px;
}

#irc {
  display: block;
   text-align: center;
  margin-top:4px;
    color: #333;
}

#irc a {
  color: #3377ee;
  font-size: 17px
}

#irc-info {
  display: block;
  text-align: center;
  font-size: 14px;
  margin-top: -10px;
  color: #828282;
  margin-bottom:4px
}

#new {
  width: 100%;
  text-align: center;
  font-size: 18px;
  font-family: Helvetica;
}

#new a {
  font-size: 18px;
  color: #4099ff;
}

js部分

document.getElementById('close').onmousedown = function(e) {
  e.preventDefault();
  document.getElementById('info').style.display = 'none';
  return false;
};

// settings

var physics_accuracy  = 3,
    mouse_influence   = 20,
    mouse_cut         = 5,
    gravity           = 1200,
    cloth_height      = 30,
    cloth_width       = 50,
    start_y           = 20,
    spacing           = 7,
    tear_distance     = 60;


window.requestAnimFrame =
    window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    function (callback) {
        window.setTimeout(callback, 1000 / 60);
};

var canvas,
    ctx,
    cloth,
    boundsx,
    boundsy,
    mouse = {
        down: false,
        button: 1,
        x: 0,
        y: 0,
        px: 0,
        py: 0
    };

var Point = function (x, y) {

    this.x      = x;
    this.y      = y;
    this.px     = x;
    this.py     = y;
    this.vx     = 0;
    this.vy     = 0;
    this.pin_x  = null;
    this.pin_y  = null;
    
    this.constraints = [];
};

Point.prototype.update = function (delta) {

    if (mouse.down) {

        var diff_x = this.x - mouse.x,
            diff_y = this.y - mouse.y,
            dist = Math.sqrt(diff_x * diff_x + diff_y * diff_y);

        if (mouse.button == 1) {

            if (dist < mouse_influence) {
                this.px = this.x - (mouse.x - mouse.px) * 1.8;
                this.py = this.y - (mouse.y - mouse.py) * 1.8;
            }

        } else if (dist < mouse_cut) this.constraints = [];
    }

    this.add_force(0, gravity);

    delta *= delta;
    nx = this.x + ((this.x - this.px) * .99) + ((this.vx / 2) * delta);
    ny = this.y + ((this.y - this.py) * .99) + ((this.vy / 2) * delta);

    this.px = this.x;
    this.py = this.y;

    this.x = nx;
    this.y = ny;

    this.vy = this.vx = 0
};

Point.prototype.draw = function () {

    if (!this.constraints.length) return;

    var i = this.constraints.length;
    while (i--) this.constraints[i].draw();
};

Point.prototype.resolve_constraints = function () {

    if (this.pin_x != null && this.pin_y != null) {

        this.x = this.pin_x;
        this.y = this.pin_y;
        return;
    }

    var i = this.constraints.length;
    while (i--) this.constraints[i].resolve();

    this.x > boundsx ? this.x = 2 * boundsx - this.x : 1 > this.x && (this.x = 2 - this.x);
    this.y < 1 ? this.y = 2 - this.y : this.y > boundsy && (this.y = 2 * boundsy - this.y);
};

Point.prototype.attach = function (point) {

    this.constraints.push(
        new Constraint(this, point)
    );
};

Point.prototype.remove_constraint = function (constraint) {

    this.constraints.splice(this.constraints.indexOf(constraint), 1);
};

Point.prototype.add_force = function (x, y) {

    this.vx += x;
    this.vy += y;
};

Point.prototype.pin = function (pinx, piny) {
    this.pin_x = pinx;
    this.pin_y = piny;
};

var Constraint = function (p1, p2) {

    this.p1     = p1;
    this.p2     = p2;
    this.length = spacing;
};

Constraint.prototype.resolve = function () {

    var diff_x  = this.p1.x - this.p2.x,
        diff_y  = this.p1.y - this.p2.y,
        dist    = Math.sqrt(diff_x * diff_x + diff_y * diff_y),
        diff    = (this.length - dist) / dist;

    if (dist > tear_distance) this.p1.remove_constraint(this);

    var px = diff_x * diff * 0.5;
    var py = diff_y * diff * 0.5;

    this.p1.x += px;
    this.p1.y += py;
    this.p2.x -= px;
    this.p2.y -= py;
};

Constraint.prototype.draw = function () {

    ctx.moveTo(this.p1.x, this.p1.y);
    ctx.lineTo(this.p2.x, this.p2.y);
};

var Cloth = function () {

    this.points = [];

    var start_x = canvas.width / 2 - cloth_width * spacing / 2;

    for (var y = 0; y <= cloth_height; y++) {

        for (var x = 0; x <= cloth_width; x++) {

            var p = new Point(start_x + x * spacing, start_y + y * spacing);

            x != 0 && p.attach(this.points[this.points.length - 1]);
            y == 0 && p.pin(p.x, p.y);
            y != 0 && p.attach(this.points[x + (y - 1) * (cloth_width + 1)])

            this.points.push(p);
        }
    }
};

Cloth.prototype.update = function () {

    var i = physics_accuracy;

    while (i--) {
        var p = this.points.length;
        while (p--) this.points[p].resolve_constraints();
    }

    i = this.points.length;
    while (i--) this.points[i].update(.016);
};

Cloth.prototype.draw = function () {

    ctx.beginPath();

    var i = cloth.points.length;
    while (i--) cloth.points[i].draw();

    ctx.stroke();
};

function update() {

    ctx.clearRect(0, 0, canvas.width, canvas.height);

    cloth.update();
    cloth.draw();

    requestAnimFrame(update);
}

function start() {

    canvas.onmousedown = function (e) {
        mouse.button  = e.which;
        mouse.px      = mouse.x;
        mouse.py      = mouse.y;
        var rect      = canvas.getBoundingClientRect();
        mouse.x       = e.clientX - rect.left,
        mouse.y       = e.clientY - rect.top,
        mouse.down    = true;
        e.preventDefault();
    };

    canvas.onmouseup = function (e) {
        mouse.down = false;
        e.preventDefault();
    };

    canvas.onmousemove = function (e) {
        mouse.px  = mouse.x;
        mouse.py  = mouse.y;
        var rect  = canvas.getBoundingClientRect();
        mouse.x   = e.clientX - rect.left,
        mouse.y   = e.clientY - rect.top,
        e.preventDefault();
    };

    canvas.oncontextmenu = function (e) {
        e.preventDefault();
    };

    boundsx = canvas.width - 1;
    boundsy = canvas.height - 1;

    ctx.strokeStyle = '#888';
  
    cloth = new Cloth();
  
    update();
}

window.onload = function () {

    canvas  = document.getElementById('c');
    ctx     = canvas.getContext('2d');

    canvas.width  = 560;
    canvas.height = 350;

    start();
};

到此这篇关于JavaScript实现扯网动画效果的示例代码的文章就介绍到这了,更多相关JavaScript扯网动画效果内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！

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