@jakebeamish/penplotting/source/Quadtree.js

A JavaScript framework for making SVG files for penplotters.

import { AABB } from "./AABB.js";

/**
 * Class representing a quadtree.
 *
 * This implementation is adapted from CodingTrain/QuadTree, which is
 * licensed under an MIT License.
 *
 * @see https://github.com/CodingTrain/QuadTree
 */
export class Quadtree {
  /**
   * Create a quadtree.
   * @param {AABB} boundary - The bounding box of the quadtree.
   * @param {number} capacity - The number of points that can be
   *                            inserted into Quadtree without subdividing.
   */
  constructor(boundary, capacity) {
    this.boundary = boundary;
    this.capacity = capacity;
    this.points = [];
    this.divided = false;
  }

  /**
   * Check for points in a given range and return them in an array.
   * @param {AABB} range - The bounding box of the query.
   * @returns {Vector[]}
   */
  query(range, found = []) {
    if (!this.boundary.intersects(range)) {
      return found;
    } else {
      for (let p of this.points) {
        if (range.contains(p)) {
          found.push(p);
        }
      }

      if (this.divided) {
        this.topLeft.query(range, found);
        this.topRight.query(range, found);
        this.bottomLeft.query(range, found);
        this.bottomRight.query(range, found);
      }
    }

    return found;
  }

  /**
   * Add a point into this quadtree.
   * @param {Vector} point
   */
  insert(point) {
    if (!this.boundary.contains(point)) {
      return;
    }

    if (this.points.length < this.capacity) {
      this.points.push(point);
    } else {
      if (!this.divided) {
        this.subdivide();
        this.divided = true;
      }

      this.topLeft.insert(point);
      this.topRight.insert(point);
      this.bottomLeft.insert(point);
      this.bottomRight.insert(point);
    }
  }

  subdivide() {
    let topLeftBoundary = new AABB(
      this.boundary.x - this.boundary.width / 2,
      this.boundary.y - this.boundary.height / 2,
      this.boundary.width / 2,
      this.boundary.height / 2,
    );
    this.topLeft = new Quadtree(topLeftBoundary, this.capacity);

    let topRightBoundary = new AABB(
      this.boundary.x + this.boundary.width / 2,
      this.boundary.y - this.boundary.height / 2,
      this.boundary.width / 2,
      this.boundary.height / 2,
    );

    this.topRight = new Quadtree(topRightBoundary, this.capacity);

    let bottomLeftBoundary = new AABB(
      this.boundary.x - this.boundary.width / 2,
      this.boundary.y + this.boundary.height / 2,
      this.boundary.width / 2,
      this.boundary.height / 2,
    );
    this.bottomLeft = new Quadtree(bottomLeftBoundary, this.capacity);

    let bottomRightBoundary = new AABB(
      this.boundary.x + this.boundary.width / 2,
      this.boundary.y + this.boundary.height / 2,
      this.boundary.width / 2,
      this.boundary.height / 2,
    );
    this.bottomRight = new Quadtree(bottomRightBoundary, this.capacity);
  }

  /**
   * For each boundary of this quadtree and all it's children,
   * create [Lines]{@link Line} from those rectangles and add them to a {@link Plot}.
   * @param {Plot} plot
   */
  show(plot) {
    plot.add(this.boundary.lines());

    if (this.divided) {
      this.topLeft.show(plot);
      this.topRight.show(plot);
      this.bottomLeft.show(plot);
      this.bottomRight.show(plot);
    }
  }
}