@zenghawtin/graph2d
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Javascript library for 2d geometry
234 lines (200 loc) • 6.82 kB
JavaScript
"use strict";
import Flatten from '../flatten';
import * as Intersection from "../algorithms/intersection";
import {Shape} from "./shape";
import {Errors} from "../utils/errors";
import {vector} from './vector'
/**
* Class representing a ray (a half-infinite line).
* @type {Ray}
*/
export class Ray extends Shape {
/**
* Ray may be constructed by setting an <b>origin</b> point and a <b>normal</b> vector, so that any point <b>x</b>
* on a ray fit an equation: <br />
* (<b>x</b> - <b>origin</b>) * <b>vector</b> = 0 <br />
* Ray defined by constructor is a right semi-infinite line with respect to the normal vector <br/>
* If normal vector is omitted ray is considered horizontal (normal vector is (0,1)). <br/>
* Don't be confused: direction of the normal vector is orthogonal to the ray <br/>
* @param {Point} pt - start point
* @param {Vector} norm - normal vector
*/
constructor(...args) {
super()
this.pt = new Flatten.Point();
this.norm = new Flatten.Vector(0,1);
if (args.length === 0) {
return;
}
if (args.length >= 1 && args[0] instanceof Flatten.Point) {
this.pt = args[0].clone();
}
if (args.length === 1) {
return;
}
if (args.length === 2 && args[1] instanceof Flatten.Vector) {
this.norm = args[1].clone();
return;
}
throw Errors.ILLEGAL_PARAMETERS;
}
/**
* Return new cloned instance of ray
* @returns {Ray}
*/
clone() {
return new Ray(this.pt, this.norm);
}
/**
* Slope of the ray - angle in radians between ray and axe x from 0 to 2PI
* @returns {number} - slope of the line
*/
get slope() {
let vec = new Flatten.Vector(this.norm.y, -this.norm.x);
return vec.slope;
}
/**
* Returns half-infinite bounding box of the ray
* @returns {Box} - bounding box
*/
get box() {
let slope = this.slope;
return new Flatten.Box(
slope > Math.PI/2 && slope < 3*Math.PI/2 ? Number.NEGATIVE_INFINITY : this.pt.x,
slope >= 0 && slope <= Math.PI ? this.pt.y : Number.NEGATIVE_INFINITY,
slope >= Math.PI/2 && slope <= 3*Math.PI/2 ? this.pt.x : Number.POSITIVE_INFINITY,
slope >= Math.PI && slope <= 2*Math.PI || slope === 0 ? this.pt.y : Number.POSITIVE_INFINITY
)
}
/**
* Return ray start point
* @returns {Point} - ray start point
*/
get start() {
return this.pt;
}
/**
* Ray has no end point?
* @returns {undefined}
*/
get end() {return undefined;}
/**
* Return positive infinity number as length
* @returns {number}
*/
get length() {return Number.POSITIVE_INFINITY;}
/**
* Returns true if point belongs to ray
* @param {Point} pt Query point
* @returns {boolean}
*/
contains(pt) {
if (this.pt.equalTo(pt)) {
return true;
}
/* Ray contains point if vector to point is orthogonal to the ray normal vector
and cross product from vector to point is positive */
let vec = new Flatten.Vector(this.pt, pt);
return Flatten.Utils.EQ_0(this.norm.dot(vec)) && Flatten.Utils.GE(vec.cross(this.norm),0);
}
/**
* Return coordinate of the point that lies on the ray in the transformed
* coordinate system where center is the projection of the point(0,0) to
* the line containing this ray and axe y is collinear to the normal vector. <br/>
* This method assumes that point lies on the ray
* @param {Point} pt - point on a ray
* @returns {number}
*/
coord(pt) {
return vector(pt.x, pt.y).cross(this.norm);
}
/**
* Split ray with point and return array of segment and new ray
* @param {Point} pt
* @returns [Segment,Ray]
*/
split(pt) {
if (!this.contains(pt))
return [];
if (this.pt.equalTo(pt)) {
return [this]
}
return [
new Flatten.Segment(this.pt, pt),
new Flatten.Ray(pt, this.norm)
]
}
/**
* Returns array of intersection points between ray and another shape
* @param {Shape} shape - Shape to intersect with ray
* @returns {Point[]} array of intersection points
*/
intersect(shape) {
if (shape instanceof Flatten.Point) {
return this.contains(shape) ? [shape] : [];
}
if (shape instanceof Flatten.Segment) {
return Intersection.intersectRay2Segment(this, shape);
}
if (shape instanceof Flatten.Arc) {
return Intersection.intersectRay2Arc(this, shape);
}
if (shape instanceof Flatten.Line) {
return Intersection.intersectRay2Line(this, shape);
}
if (shape instanceof Flatten.Ray) {
return Intersection.intersectRay2Ray(this, shape)
}
if (shape instanceof Flatten.Circle) {
return Intersection.intersectRay2Circle(this, shape);
}
if (shape instanceof Flatten.Box) {
return Intersection.intersectRay2Box(this, shape);
}
if (shape instanceof Flatten.Polygon) {
return Intersection.intersectRay2Polygon(this, shape);
}
}
/**
* Return new line rotated by angle
* @param {number} angle - angle in radians
* @param {Point} center - center of rotation
*/
rotate(angle, center = new Flatten.Point()) {
return new Flatten.Ray(
this.pt.rotate(angle, center),
this.norm.rotate(angle)
)
}
/**
* Return new ray transformed by affine transformation matrix
* @param {Matrix} m - affine transformation matrix (a,b,c,d,tx,ty)
* @returns {Ray}
*/
transform(m) {
return new Flatten.Ray(
this.pt.transform(m),
this.norm.clone()
)
}
get name() {
return "ray"
}
/**
* Return string to draw svg segment representing ray inside given box
* @param {Box} box Box representing drawing area
* @param {Object} attrs - an object with attributes of svg segment element
*/
svg(box, attrs = {}) {
let line = new Flatten.Line(this.pt, this.norm);
let ip = Intersection.intersectLine2Box(line, box);
ip = ip.filter( pt => this.contains(pt) );
if (ip.length === 0 || ip.length === 2)
return "";
let segment = new Flatten.Segment(this.pt, ip[0]);
return segment.svg(attrs);
}
}
Flatten.Ray = Ray;
export const ray = (...args) => new Flatten.Ray(...args);
Flatten.ray = ray;