@flatten-js/core
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Javascript library for 2d geometry
498 lines (443 loc) • 17.3 kB
JavaScript
/**
* Created by Alex Bol on 3/17/2017.
*/
"use strict";
import Flatten from '../flatten';
import CircularLinkedList from '../data_structures/circular_linked_list';
import {CCW, ORIENTATION} from '../utils/constants';
/**
* Class representing a face (closed loop) in a [polygon]{@link Flatten.Polygon} object.
* Face is a circular bidirectionally linked list of [edges]{@link Flatten.Edge}.
* Face object cannot be instantiated with a constructor.
* Instead, use [polygon.addFace()]{@link Flatten.Polygon#addFace} method.
* <br/>
* 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. <br/>
*
* @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(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;
}
/**
* Get all edges length
* @returns {number}
*/
get perimeter() {
return this.last.arc_length + this.last.length
}
/**
* Get point on face boundary at given length
* @param {number} length - The length along the face boundary
* @returns {Point}
*/
pointAtLength(length) {
if (length > this.perimeter || length < 0) return null;
let point = null;
for (let edge of this) {
if (length >= edge.arc_length &&
(edge === this.last || length < edge.next.arc_length)) {
point = edge.pointAtLength(length - edge.arc_length);
break;
}
}
return point;
}
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). <br/>
* @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 <br/>
* @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 <br/>
* @param {Edge} edge - Edge to be removed
* @returns {Face}
*/
remove(edge) {
super.remove(edge);
// Recalculate arc length
this.setArcLength();
return this;
}
/**
* Merge current edge with the next edge. Given edge will be extended,
* next edge after it will be removed. The distortion of the polygon
* is on the responsibility of the user of this method
* @param {Edge} edge - edge to be extended
* @returns {Face}
*/
merge_with_next_edge(edge) {
edge.shape.end.x = edge.next.shape.end.x
edge.shape.end.y = edge.next.shape.end.y
this.remove(edge.next)
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 counterclockwise 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 <br/>
* 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 counterclockwise,
* 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 = ORIENTATION.NOT_ORIENTABLE;
} else if (Flatten.Utils.LT(area, 0)) {
this._orientation = ORIENTATION.CCW;
} else {
this._orientation = 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 {PlanarSet} 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 between edge1 and edge2
let ip = edge1.shape.intersect(edge2.shape);
// for each intersection point
for (let pt of ip) {
// skip start-end connections
if (pt.equalTo(edge1.start) && pt.equalTo(edge2.end) && edge2 === edge1.prev)
continue;
if (pt.equalTo(edge1.end) && pt.equalTo(edge2.start) && edge2 === edge1.next)
continue;
int_points.push(pt);
if (exitOnFirst)
break;
}
if (int_points.length > 0 && exitOnFirst)
break;
}
if (int_points.length > 0 && exitOnFirst)
break;
}
return int_points;
}
/**
* Returns edge which contains given point
* @param {Point} pt - test point
* @returns {Edge}
*/
findEdgeByPoint(pt) {
let edgeFound;
for (let edge of this) {
if (pt.equalTo(edge.shape.start)) continue
if (pt.equalTo(edge.shape.end) || edge.shape.contains(pt)) {
edgeFound = edge;
break;
}
}
return edgeFound;
}
/**
* Returns new polygon created from one face
* @returns {Polygon}
*/
toPolygon() {
return new Flatten.Polygon(this.shapes);
}
toJSON() {
return this.edges.map(edge => edge.toJSON());
}
/**
* Returns string to be assigned to "d" attribute inside defined "path"
* @returns {string}
*/
svg() {
let svgStr = `M${this.first.start.x},${this.first.start.y}`;
for (let edge of this) {
svgStr += edge.svg();
}
svgStr += ` z`;
return svgStr;
}
}
Flatten.Face = Face;