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+/*
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+Copyright (c) 2013 Suffick at Codepen (http://codepen.io/suffick) and GitHub (https://github.com/suffick)
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+Permission is hereby granted, free of charge, to any person obtaining a copy
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+of this software and associated documentation files (the "Software"), to deal
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+in the Software without restriction, including without limitation the rights
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+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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+copies of the Software, and to permit persons to whom the Software is
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+furnished to do so, subject to the following conditions:
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+The above copyright notice and this permission notice shall be included in
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+all copies or substantial portions of the Software.
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+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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+THE SOFTWARE.
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+*/
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+
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+// settings
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+
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+var physics_accuracy = 3,
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+ mouse_influence = 20,
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+ mouse_cut = 5,
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+ gravity = 1200,
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+ cloth_height = 40,
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+ cloth_width = 76,
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+ start_y = 10,
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+ spacing = 7,
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+ tear_distance = 600;
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+
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+
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+window.requestAnimFrame =
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+ window.requestAnimationFrame ||
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+ window.webkitRequestAnimationFrame ||
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+ window.mozRequestAnimationFrame ||
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+ window.oRequestAnimationFrame ||
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+ window.msRequestAnimationFrame ||
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+ function (callback) {
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+ window.setTimeout(callback, 1000 / 60);
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+};
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+
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+var canvas,
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+ ctx,
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+ cloth,
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+ boundsx,
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+ boundsy,
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+ mouse = {
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+ down: false,
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+ button: 1,
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+ x: 0,
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+ y: 0,
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+ px: 0,
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+ py: 0
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+ };
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+
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+var Point = function (x, y) {
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+
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+ this.x = x;
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+ this.y = y;
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+ this.px = x;
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+ this.py = y;
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+ this.vx = 0;
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+ this.vy = 0;
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+ this.pin_x = null;
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+ this.pin_y = null;
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+
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+ this.constraints = [];
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+};
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+
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+Point.prototype.update = function (delta) {
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+
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+ if (mouse.down) {
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+
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+ var diff_x = this.x - mouse.x,
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+ diff_y = this.y - mouse.y,
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+ dist = Math.sqrt(diff_x * diff_x + diff_y * diff_y);
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+
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+ if (mouse.button == 1) {
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+
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+ if (dist < mouse_influence) {
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+ this.px = this.x - (mouse.x - mouse.px) * 1.8;
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+ this.py = this.y - (mouse.y - mouse.py) * 1.8;
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+ }
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+
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+ } else if (dist < mouse_cut) this.constraints = [];
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+ }
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+
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+ this.add_force(0, gravity);
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+
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+ delta *= delta;
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+ nx = this.x + ((this.x - this.px) * .99) + ((this.vx / 2) * delta);
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+ ny = this.y + ((this.y - this.py) * .99) + ((this.vy / 2) * delta);
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+
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+ this.px = this.x;
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+ this.py = this.y;
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+
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+ this.x = nx;
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+ this.y = ny;
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+
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+ this.vy = this.vx = 0
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+};
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+
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+Point.prototype.draw = function () {
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+
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+ if (this.constraints.length <= 0) return;
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+
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+ var i = this.constraints.length;
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+ while (i--) this.constraints[i].draw();
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+};
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+
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+Point.prototype.resolve_constraints = function () {
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+
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+ if (this.pin_x != null && this.pin_y != null) {
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+
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+ this.x = this.pin_x;
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+ this.y = this.pin_y;
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+ return;
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+ }
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+
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+ var i = this.constraints.length;
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+ while (i--) this.constraints[i].resolve();
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+
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+ if (this.x > boundsx) {
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+
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+ this.x = 2 * boundsx - this.x;
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+
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+ } else if (this.x < 1) {
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+
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+ this.x = 2 - this.x;
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+ }
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+
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+ if (this.y > boundsy) {
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+
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+ this.y = 2 * boundsy - this.y;
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+
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+ } else if (this.y < 1) {
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+
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+ this.y = 2 - this.y;
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+ }
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+};
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+
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+Point.prototype.attach = function (point) {
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+
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+ this.constraints.push(
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+ new Constraint(this, point)
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+ );
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+};
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+
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+Point.prototype.remove_constraint = function (lnk) {
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+
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+ var i = this.constraints.length;
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+ while (i--)
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+ if (this.constraints[i] == lnk) this.constraints.splice(i, 1);
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+};
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+
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+Point.prototype.add_force = function (x, y) {
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+
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+ this.vx += x;
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+ this.vy += y;
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+};
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+
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+Point.prototype.pin = function (pinx, piny) {
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+ this.pin_x = pinx;
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+ this.pin_y = piny;
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+};
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+
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+var Constraint = function (p1, p2) {
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+
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+ this.p1 = p1;
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+ this.p2 = p2;
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+ this.length = spacing;
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+};
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+
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+Constraint.prototype.resolve = function () {
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+
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+ var diff_x = this.p1.x - this.p2.x,
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+ diff_y = this.p1.y - this.p2.y,
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+ dist = Math.sqrt(diff_x * diff_x + diff_y * diff_y),
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+ diff = (this.length - dist) / dist;
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+
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+ if (dist > tear_distance) this.p1.remove_constraint(this);
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+
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+ var px = diff_x * diff * 0.5;
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+ var py = diff_y * diff * 0.5;
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+
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+ this.p1.x += px;
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+ this.p1.y += py;
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+ this.p2.x -= px;
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+ this.p2.y -= py;
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+};
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+
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+Constraint.prototype.draw = function () {
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+
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+ ctx.moveTo(this.p1.x, this.p1.y);
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+ ctx.lineTo(this.p2.x, this.p2.y);
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+};
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+
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+var Cloth = function () {
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+
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+ this.points = [];
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+
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+ var start_x = canvas.width / 2 - cloth_width * spacing / 2;
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+
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+ for (var y = 0; y <= cloth_height; y++) {
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+
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+ for (var x = 0; x <= cloth_width; x++) {
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+
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+ var p = new Point(start_x + x * spacing, start_y + y * spacing);
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+
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+ x != 0 && p.attach(this.points[this.points.length - 1]);
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+ y == 0 && p.pin(p.x, p.y);
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+ y != 0 && p.attach(this.points[x + (y - 1) * (cloth_width + 1)])
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+
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+ this.points.push(p);
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+ }
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+ }
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+};
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+
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+Cloth.prototype.update = function () {
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+
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+ var i = physics_accuracy;
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+
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+ while (i--) {
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+ var p = this.points.length;
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+ while (p--) this.points[p].resolve_constraints();
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+ }
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+
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+ i = this.points.length;
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+ while (i--) this.points[i].update(.016);
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+};
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+
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+Cloth.prototype.draw = function () {
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+
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+ ctx.beginPath();
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+
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+ var i = cloth.points.length;
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+ while (i--) cloth.points[i].draw();
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+
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+ ctx.stroke();
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+};
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+
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+function update() {
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+
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+ ctx.clearRect(0, 0, canvas.width, canvas.height);
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+
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+ cloth.update();
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+ cloth.draw();
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+
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+ requestAnimFrame(update);
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+}
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+
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+function start() {
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+
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+ canvas.onmousedown = function (e) {
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+ mouse.button = e.which;
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+ mouse.px = mouse.x;
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+ mouse.py = mouse.y;
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+ var rect = canvas.getBoundingClientRect();
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+ mouse.x = e.clientX - rect.left,
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+ mouse.y = e.clientY - rect.top,
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+ mouse.down = true;
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+ e.preventDefault();
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+ };
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+
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+ canvas.onmouseup = function (e) {
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+ mouse.down = false;
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+ e.preventDefault();
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+ };
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+
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+ canvas.onmousemove = function (e) {
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+ mouse.px = mouse.x;
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+ mouse.py = mouse.y;
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+ var rect = canvas.getBoundingClientRect();
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+ mouse.x = e.clientX - rect.left,
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+ mouse.y = e.clientY - rect.top,
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+ e.preventDefault();
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+ };
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+
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+ canvas.oncontextmenu = function (e) {
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+ e.preventDefault();
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+ };
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+
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+ boundsx = canvas.width - 1;
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+ boundsy = canvas.height - 1;
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+
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+ ctx.strokeStyle = '#888';
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+ cloth = new Cloth();
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+ update();
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+}
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+
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+window.onload = function () {
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+
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+ canvas = document.getElementById('canvas');
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+ ctx = canvas.getContext('2d');
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+
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+ canvas.width = 560;
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+ canvas.height = 350;
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+
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+ start();
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+};
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