Разрываемая ткань — различия между версиями

/*
 Copyright (c) 2013 Suffick at Codepen (http://codepen.io/suffick), GitHub (https://github.com/suffick) and lonely-pixel.com

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */

// Настройки

var physics_accuracy  = 3,          // точность расчетов
    mouse_influence   = 20,         // радиус захвата ткани курсором
    mouse_cut         = 5,          // радиус обрезания ткани курсором (по правой кнопке мыши)
    gravity           = 1200,       // гравитация
    cloth_height      = 30,         // ширина ткани
    cloth_width       = 50,         // высота ткани
    start_y           = 20,         // высота закрепления ткани
    spacing           = 7,          // расстояние между узлами ткани
    tear_distance     = 60;         // прочность ткани


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);               // эта функция через некоторое время снова вызовет update(), так реализуется анимация
}

// Инициализация и запуск программы
function start() {

    // функция выполняется при нажатии кнопки мыши
    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();
    };

    // функция выполняется при отпускании клавиши мыши
    window.onmouseup = function (e) {       // на элементе window, чтобы не происходило залипания клавиши мыши
        mouse.down = false;
        e.preventDefault();
    };

    // функция выполняется при движении мыши
    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();
    };

    // функция предотвращает появление контекстного меню
    canvas.oncontextmenu = function (e) {
        e.preventDefault();
    };

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

    ctx.strokeStyle = '#888';               // цвет ткани

    cloth = new Cloth();

    update();                               // начало расчетов/рисования
}

window.onload = function () {               // эта функция выполняется при загрузке страницы

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

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

    start();
};

<canvas id="c"></canvas>
<script src="Tearable_Cloth.js"></script>