flatten-js
Version:
Javascript library for 2d geometry
270 lines (226 loc) • 9.4 kB
JavaScript
/**
* Created by Alex Bol on 3/6/2017.
*/
"use strict";
module.exports = function(Flatten) {
let {Arc,vector} = Flatten;
/**
* Class representing a circle
* @type {Circle}
*/
Flatten.Circle = class Circle {
/**
*
* @param {Point} pc - circle center point
* @param {number} r - circle radius
*/
constructor(...args) {
/**
* Circle center
* @type {Point}
*/
this.pc = new Flatten.Point();
/**
* Circle radius
* @type {number}
*/
this.r = 1;
if (args.length == 1 && args[0] instanceof Object && args[0].name === "circle") {
let {pc, r} = args[0];
this.pc = new Flatten.Point(pc);
this.r = r;
return;
}
else {
let [pc, r] = [...args];
if (pc && pc instanceof Flatten.Point) this.pc = pc.clone();
if (r !== undefined) this.r = r;
return;
}
throw Flatten.Errors.ILLEGAL_PARAMETERS;
}
/**
* Method clone returns new instance of a Circle
* @returns {Circle}
*/
clone() {
return new Flatten.Circle(this.pc.clone(), this.r);
}
/**
* Circle center
* @returns {Point}
*/
get center() {
return this.pc;
}
/**
* Circle bounding box
* @returns {Box}
*/
get box() {
return new Flatten.Box(
this.pc.x - this.r,
this.pc.y - this.r,
this.pc.x + this.r,
this.pc.y + this.r
);
}
/**
* Return true if circle contains point
* @param {Point} pt - test point
* @returns {boolean}
*/
contains(pt) {
return Flatten.Utils.LE(pt.distanceTo(this.center)[0], this.r);
}
/**
* Transform circle to closed arc
* @param {boolean} counterclockwise
* @returns {Arc}
*/
toArc(counterclockwise=true) {
return new Flatten.Arc(this.center, this.r, Math.PI, -Math.PI, counterclockwise);
}
/**
* Returns array of intersection points between circle and other shape
* @param {Shape} shape Shape of the one of supported types
* @returns {Point[]}
*/
intersect(shape) {
if (shape instanceof Flatten.Point) {
return this.contains(shape) ? [shape] : [];
}
if (shape instanceof Flatten.Line) {
return shape.intersect(this);
}
if (shape instanceof Flatten.Segment) {
return shape.intersect(this);
}
if (shape instanceof Flatten.Circle) {
return Circle.intersectCirle2Circle(this, shape);
}
if (shape instanceof Flatten.Arc) {
return shape.intersect(this);
}
if (shape instanceof Flatten.Polygon) {
return Flatten.Polygon.intersectShape2Polygon(this, shape);
}
}
/**
* Calculate distance and shortest segment from circle to shape and return array [distance, shortest segment]
* @param {Shape} shape Shape of the one of supported types Point, Line, Circle, Segment, Arc, Polygon or Planar Set
* @returns {number} distance from circle to shape
* @returns {Segment} shortest segment between circle and shape (started at circle, ended at shape)
*/
distanceTo(shape) {
let {Distance} = Flatten;
let {point2circle, circle2circle, circle2line, segment2circle, arc2circle} = Distance;
if (shape instanceof Flatten.Point) {
let [distance, shortest_segment] = point2circle(shape, this);
shortest_segment = shortest_segment.reverse();
return [distance, shortest_segment];
}
if (shape instanceof Flatten.Circle) {
let [distance, shortest_segment] = circle2circle(this, shape);
return [distance, shortest_segment];
}
if (shape instanceof Flatten.Line) {
let [distance, shortest_segment] = circle2line(this, shape);
return [distance, shortest_segment];
}
if (shape instanceof Flatten.Segment) {
let [distance, shortest_segment] = segment2circle(shape, this);
shortest_segment = shortest_segment.reverse();
return [distance, shortest_segment];
}
if (shape instanceof Flatten.Arc) {
let [distance, shortest_segment] = arc2circle(shape, this);
shortest_segment = shortest_segment.reverse();
return [distance, shortest_segment];
}
if (shape instanceof Flatten.Polygon) {
let [distance, shortest_segment] = Distance.shape2polygon(this, shape);
return [distance, shortest_segment];
}
if (shape instanceof Flatten.PlanarSet) {
let [dist, shortest_segment] = Distance.shape2planarSet(this, shape);
return [dist, shortest_segment];
}
}
static intersectCirle2Circle(circle1, circle2) {
let ip = [];
if (circle1.box.not_intersect(circle2.box)) {
return ip;
}
let vec = new Flatten.Vector(circle1.pc, circle2.pc);
let r1 = circle1.r;
let r2 = circle2.r;
// Degenerated circle
if (Flatten.Utils.EQ_0(r1) || Flatten.Utils.EQ_0(r2))
return ip;
// In case of equal circles return one leftmost point
if (Flatten.Utils.EQ_0(vec.x) && Flatten.Utils.EQ_0(vec.y) && Flatten.Utils.EQ(r1, r2)) {
ip.push(circle1.pc.translate(-r1, 0));
return ip;
}
let dist = circle1.pc.distanceTo(circle2.pc)[0];
if (Flatten.Utils.GT(dist, r1 + r2)) // circles too far, no intersections
return ip;
if (Flatten.Utils.LT(dist, Math.abs(r1 - r2))) // one circle is contained within another, no intersections
return ip;
// Normalize vector.
vec.x /= dist;
vec.y /= dist;
let pt;
// Case of touching from outside or from inside - single intersection point
// TODO: check this specifically not sure if correct
if (Flatten.Utils.EQ(dist, r1 + r2) || Flatten.Utils.EQ(dist, Math.abs(r1 - r2))) {
pt = circle1.pc.translate(r1*vec.x, r1*vec.y);
ip.push(pt);
return ip;
}
// Case of two intersection points
// Distance from first center to center of common chord:
// a = (r1^2 - r2^2 + d^2) / 2d
// Separate for better accuracy
let a = (r1*r1)/(2*dist) - (r2*r2)/(2*dist) + dist/2;
let mid_pt = circle1.pc.translate(a*vec.x, a*vec.y);
let h = Math.sqrt(r1*r1 - a*a);
// let norm;
// norm = vec.rotate90CCW().multiply(h);
pt = mid_pt.translate(vec.rotate90CCW().multiply(h));
ip.push(pt);
// norm = vec.rotate90CW();
pt = mid_pt.translate(vec.rotate90CW().multiply(h));
ip.push(pt);
return ip;
}
/**
* Return string to draw circle in svg
* @param {Object} attrs - an object with attributes of svg circle element,
* like "stroke", "strokeWidth", "fill" <br/>
* Defaults are stroke:"black", strokeWidth:"1", fill:"none"
* @returns {string}
*/
svg(attrs = {}) {
let {stroke, strokeWidth, fill, fillOpacity, id, className} = attrs;
// let rest_str = Object.keys(rest).reduce( (acc, key) => acc += ` ${key}="${rest[key]}"`, "");
let id_str = (id && id.length > 0) ? `id="${id}"` : "";
let class_str = (className && className.length > 0) ? `class="${className}"` : "";
return `\n<circle cx="${this.pc.x}" cy="${this.pc.y}" r="${this.r}" stroke="${stroke || "black"}" stroke-width="${strokeWidth || 1}" fill="${fill || "none"}" fill-opacity="${fillOpacity || 1.0}" ${id_str} ${class_str} />`;
}
/**
* This method returns an object that defines how data will be
* serialized when called JSON.stringify() method
* @returns {Object}
*/
toJSON() {
return Object.assign({},this,{name:"circle"});
}
};
/**
* Shortcut to create new circle
* @param args
*/
Flatten.circle = (...args) => new Flatten.Circle(...args);
};