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File: src/geometry/Axes.js

                                /**
                                * The `Matter.Axes` module contains methods for creating and manipulating sets of axes.
                                *
                                * @class Axes
                                */
                                
                                var Axes = {};
                                
                                module.exports = Axes;
                                
                                var Vector = require('../geometry/Vector');
                                var Common = require('../core/Common');
                                
                                (function() {
                                
                                    /**
                                     * Creates a new set of axes from the given vertices.
                                     * @method fromVertices
                                     * @param {vertices} vertices
                                     * @return {axes} A new axes from the given vertices
                                     */
                                    Axes.fromVertices = function(vertices) {
                                        var axes = {};
                                
                                        // find the unique axes, using edge normal gradients
                                        for (var i = 0; i < vertices.length; i++) {
                                            var j = (i + 1) % vertices.length, 
                                                normal = Vector.normalise({ 
                                                    x: vertices[j].y - vertices[i].y, 
                                                    y: vertices[i].x - vertices[j].x
                                                }),
                                                gradient = (normal.y === 0) ? Infinity : (normal.x / normal.y);
                                            
                                            // limit precision
                                            gradient = gradient.toFixed(3).toString();
                                            axes[gradient] = normal;
                                        }
                                
                                        return Common.values(axes);
                                    };
                                
                                    /**
                                     * Rotates a set of axes by the given angle.
                                     * @method rotate
                                     * @param {axes} axes
                                     * @param {number} angle
                                     */
                                    Axes.rotate = function(axes, angle) {
                                        if (angle === 0)
                                            return;
                                        
                                        var cos = Math.cos(angle),
                                            sin = Math.sin(angle);
                                
                                        for (var i = 0; i < axes.length; i++) {
                                            var axis = axes[i],
                                                xx;
                                            xx = axis.x * cos - axis.y * sin;
                                            axis.y = axis.x * sin + axis.y * cos;
                                            axis.x = xx;
                                        }
                                    };
                                
                                })();
                                
                                    
0.18.0