@flatten-js/core

<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width,initial-scale=1"> <title>classes/face.js - Documentation</title> <script src="scripts/prettify/prettify.js"></script> <script src="scripts/prettify/lang-css.js"></script>  <link type="text/css" rel="stylesheet" href="https://code.ionicframework.com/ionicons/2.0.1/css/ionicons.min.css"> <link type="text/css" rel="stylesheet" href="styles/prettify-tomorrow.css"> <link type="text/css" rel="stylesheet" href="styles/jsdoc-default.css"> </head> <body> <input type="checkbox" id="nav-trigger" class="nav-trigger" /> <label for="nav-trigger" class="navicon-button x"> <div class="navicon"></div> </label> <label for="nav-trigger" class="overlay"></label> <nav> <li class="nav-link nav-home-link"><a href="index.html">Home</a></li><li class="nav-heading">Classes</li><li class="nav-heading">C<a href="Arc.html">Arc</a></li><li class="nav-item">F<a href="Arc.html#clone">clone</a></li><li 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linenums"><code>/** * Created by Alex Bol on 3/17/2017. */ "use strict"; import Flatten from '../flatten'; import CircularLinkedList from '../data_structures/circular_linked_list'; /** * Class representing a face (closed loop) in a [polygon]{@link Flatten.Polygon} object. * Face is a circular bidirectional linked list of [edges]{@link Flatten.Edge}. * Face object cannot be instantiated with a constructor. * Instead, use [polygon.addFace()]{@link Flatten.Polygon#addFace} method. * * Note, that face only set entry point to the linked list of edges but does not contain edges by itself. * Container of edges is a property of the polygon object. * * @example * // Face implements "next" iterator which enables to iterate edges in for loop: * for (let edge of face) { * console.log(edge.shape.length) // do something * } * * // Instead, it is possible to iterate edges as linked list, starting from face.first: * let edge = face.first; * do { * console.log(edge.shape.length); // do something * edge = edge.next; * } while (edge != face.first) */ export class Face extends CircularLinkedList { constructor(polygon, ...args) { super(); // construct empty list of edges /** * Reference to the first edge in face */ // this.first; /** * Reference to the last edge in face */ // this.last; this._box = undefined; // new Box(); this._orientation = undefined; if (args.length == 0) { return; } /* If passed an array it supposed to be: 1) array of shapes that performs close loop or 2) array of points that performs set of vertices */ if (args.length == 1) { if (args[0] instanceof Array) { // let argsArray = args[0]; let shapes = args[0]; // argsArray[0]; if (shapes.length == 0) return; /* array of Flatten.Points */ if (shapes.every((shape) => {return shape instanceof Flatten.Point})) { let segments = Face.points2segments(shapes); this.shapes2face(polygon.edges, segments); } /* array of points as pairs of numbers */ else if (shapes.every((shape) => {return shape instanceof Array && shape.length === 2})) { let points = shapes.map((shape) => new Flatten.Point(shape[0],shape[1])); let segments = Face.points2segments(points); this.shapes2face(polygon.edges, segments); } /* array of segments ot arcs */ else if (shapes.every((shape) => { return (shape instanceof Flatten.Segment || shape instanceof Flatten.Arc) })) { this.shapes2face(polygon.edges, shapes); } // this is from JSON.parse object else if (shapes.every((shape) => { return (shape.name === "segment" || shape.name === "arc") })) { let flattenShapes = []; for (let shape of shapes) { let flattenShape; if (shape.name === "segment") { flattenShape = new Flatten.Segment(shape); } else { flattenShape = new Flatten.Arc(shape); } flattenShapes.push(flattenShape); } this.shapes2face(polygon.edges, flattenShapes); } } /* Create new face and copy edges into polygon.edges set */ else if (args[0] instanceof Face) { let face = args[0]; this.first = face.first; this.last = face.last; for (let edge of face) { polygon.edges.add(edge); } } /* Instantiate face from a circle in CCW orientation */ else if (args[0] instanceof Flatten.Circle) { this.shapes2face(polygon.edges, [args[0].toArc(Flatten.CCW)]); } /* Instantiate face from a box in CCW orientation */ else if (args[0] instanceof Flatten.Box) { let box = args[0]; this.shapes2face(polygon.edges, [ new Flatten.Segment(new Flatten.Point(box.xmin, box.ymin), new Flatten.Point(box.xmax, box.ymin)), new Flatten.Segment(new Flatten.Point(box.xmax, box.ymin), new Flatten.Point(box.xmax, box.ymax)), new Flatten.Segment(new Flatten.Point(box.xmax, box.ymax), new Flatten.Point(box.xmin, box.ymax)), new Flatten.Segment(new Flatten.Point(box.xmin, box.ymax), new Flatten.Point(box.xmin, box.ymin)) ]); } } /* If passed two edges, consider them as start and end of the face loop */ /* THIS METHOD WILL BE USED BY BOOLEAN OPERATIONS */ /* Assume that edges already copied to polygon.edges set in the clip algorithm !!! */ if (args.length == 2 && args[0] instanceof Flatten.Edge && args[1] instanceof Flatten.Edge) { this.first = args[0]; // first edge in face or undefined this.last = args[1]; // last edge in face or undefined this.last.next = this.first; this.first.prev = this.last; // set arc length this.setArcLength(); // this.box = this.getBox(); // this.orientation = this.getOrientation(); // face direction cw or ccw } } /** * Return array of edges from first to last * @returns {Array} */ get edges() { return this.toArray(); } /** * Return array of shapes which comprise face * @returns {Array} */ get shapes() { return this.edges.map(edge => edge.shape.clone()); } /** * Return bounding box of the face * @returns {Box} */ get box() { if (this._box === undefined) { let box = new Flatten.Box(); for (let edge of this) { box = box.merge(edge.box); } this._box = box; } return this._box; } static points2segments(points) { let segments = []; for (let i = 0; i < points.length; i++) { // skip zero length segment if (points[i].equalTo(points[(i + 1) % points.length])) continue; segments.push(new Flatten.Segment(points[i], points[(i + 1) % points.length])); } return segments; } shapes2face(edges, shapes) { for (let shape of shapes) { let edge = new Flatten.Edge(shape); this.append(edge); // this.box = this.box.merge(shape.box); edges.add(edge); } // this.orientation = this.getOrientation(); // face direction cw or ccw } /** * Append edge after the last edge of the face (and before the first edge). * @param {Edge} edge - Edge to be appended to the linked list * @returns {Face} */ append(edge) { super.append(edge); // set arc length this.setOneEdgeArcLength(edge); edge.face = this; // edges.add(edge); // Add new edges into edges container return this; } /** * Insert edge newEdge into the linked list after the edge edgeBefore * @param {Edge} newEdge - Edge to be inserted into linked list * @param {Edge} edgeBefore - Edge to insert newEdge after it * @returns {Face} */ insert(newEdge, edgeBefore) { super.insert(newEdge, edgeBefore); // set arc length this.setOneEdgeArcLength(newEdge); newEdge.face = this; return this; } /** * Remove the given edge from the linked list of the face * @param {Edge} edge - Edge to be removed * @returns {Face} */ remove(edge) { super.remove(edge); // Recalculate arc length this.setArcLength(); return this; } /** * Reverse orientation of the face: first edge become last and vice a verse, * all edges starts and ends swapped, direction of arcs inverted. If face was oriented * clockwise, it becomes counter clockwise and vice versa */ reverse() { // collect edges in revert order with reverted shapes let edges = []; let edge_tmp = this.last; do { // reverse shape edge_tmp.shape = edge_tmp.shape.reverse(); edges.push(edge_tmp); edge_tmp = edge_tmp.prev; } while (edge_tmp !== this.last); // restore linked list this.first = undefined; this.last = undefined; for (let edge of edges) { if (this.first === undefined) { edge.prev = edge; edge.next = edge; this.first = edge; this.last = edge; } else { // append to end edge.prev = this.last; this.last.next = edge; // update edge to be last this.last = edge; // restore circular links this.last.next = this.first; this.first.prev = this.last; } // set arc length this.setOneEdgeArcLength(edge); } // Recalculate orientation, if set if (this._orientation !== undefined) { this._orientation = undefined; this._orientation = this.orientation(); } } /** * Set arc_length property for each of the edges in the face. * Arc_length of the edge it the arc length from the first edge of the face */ setArcLength() { for (let edge of this) { this.setOneEdgeArcLength(edge); edge.face = this; } } setOneEdgeArcLength(edge) { if (edge === this.first) { edge.arc_length = 0.0; } else { edge.arc_length = edge.prev.arc_length + edge.prev.length; } } /** * Returns the absolute value of the area of the face * @returns {number} */ area() { return Math.abs(this.signedArea()); } /** * Returns signed area of the simple face. * Face is simple if it has no self intersections that change its orientation. * Then the area will be positive if the orientation of the face is clockwise, * and negative if orientation is counterclockwise. * It may be zero if polygon is degenerated. * @returns {number} */ signedArea() { let sArea = 0; let ymin = this.box.ymin; for (let edge of this) { sArea += edge.shape.definiteIntegral(ymin); } return sArea; } /** * Return face orientation: one of Flatten.ORIENTATION.CCW, Flatten.ORIENTATION.CW, Flatten.ORIENTATION.NOT_ORIENTABLE * According to Green theorem the area of a closed curve may be calculated as double integral, * and the sign of the integral will be defined by the direction of the curve. * When the integral ("signed area") will be negative, direction is counter clockwise, * when positive - clockwise and when it is zero, polygon is not orientable. * See {@link https://mathinsight.org/greens_theorem_find_area} * @returns {number} */ orientation() { if (this._orientation === undefined) { let area = this.signedArea(); if (Flatten.Utils.EQ_0(area)) { this._orientation = Flatten.ORIENTATION.NOT_ORIENTABLE; } else if (Flatten.Utils.LT(area, 0)) { this._orientation = Flatten.ORIENTATION.CCW; } else { this._orientation = Flatten.ORIENTATION.CW; } } return this._orientation; } /** * Returns true if face of the polygon is simple (no self-intersection points found) * NOTE: this method is incomplete because it does not exclude touching points. * Self intersection test should check if polygon change orientation in the test point. * @param {Edges} edges - reference to polygon.edges to provide search index * @returns {boolean} */ isSimple(edges) { let ip = Face.getSelfIntersections(this, edges, true); return ip.length == 0; } static getSelfIntersections(face, edges, exitOnFirst = false) { let int_points = []; // calculate intersections for (let edge1 of face) { // request edges of polygon in the box of edge1 let resp = edges.search(edge1.box); // for each edge2 in response for (let edge2 of resp) { // Skip itself if (edge1 === edge2) continue; // Skip is edge2 belongs to another face if (edge2.face !== face) continue; // Skip next and previous edge if both are segment (if one of them arc - calc intersection) if (edge1.shape instanceof Flatten.Segment && edge2.shape instanceof Flatten.Segment && (edge1.next === edge2 || edge1.prev === edge2)) continue; // calculate intersections