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'use strict';
class AABB {
constructor(x, y, width, height) {
this.x = x; this.y = y;
this.width = width; this.height = height;
}
contains(point) {
if (point.x >= this.x && point.y >= this.y
&& point.x < this.x + this.width
&& point.y < this.y + this.height)
return true;
return false;
}
intersects(aabb) {
const overlap = (ax, arange, bx, brange) => {
const range = ax < bx ? arange : brange;
if (Math.abs(bx - ax) < range)
return true;
return false;
};
if (overlap(this.x, this.width, aabb.x, aabb.width) &&
overlap(this.y, this.height, aabb.y, aabb.height))
return true;
return false;
}
}
/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* QUADTREE
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
class QTNodeType {
constructor(name) { this.name = name; }
toString() { return `QTNode.${this.name}`; }
}
class QTNode {
static Empty = new QTNodeType('Empty');
static Leaf = new QTNodeType('Leaf');
static Branch = new QTNodeType('Branch');
constructor(x, y, width, height) {
this.aabb = new AABB(x, y, width, height);
this.type = QTNode.Empty;
}
insert(point) {
if (this.aabb.contains(point)) {
if (this.type == QTNode.Empty) {
this.type = QTNode.Leaf;
this.point = point;
return true;
}
else if (this.type == QTNode.Leaf) {
this.type = QTNode.Branch;
this.subdivide();
let result = this.insert(this.point);
if (!result) return false;
this.point = undefined;
return this.insert(point);
}
else {
// Branch
if (this.subnode[0].insert(point)) return true;
if (this.subnode[1].insert(point)) return true;
if (this.subnode[2].insert(point)) return true;
if (this.subnode[3].insert(point)) return true;
return false; // something strange has happened!!
}
}
return false;
}
subdivide() {
const x = this.aabb.x; const y = this.aabb.y;
const w = this.aabb.width/2; const h = this.aabb.height/2;
this.subnode = [
new QTNode(x, y, w, h),
new QTNode(x+w, y, w, h),
new QTNode(x, y+h, w, h),
new QTNode(x+w, y+h, w, h),
];
}
getPointsInRegion(aabb) {
if (this.type == QTNode.Empty) return [];
if (!this.aabb.intersects(aabb)) return [];
if (this.type == QTNode.Leaf) return [this.point];
return [
...this.subnode[0].getPointsInRegion(aabb),
...this.subnode[1].getPointsInRegion(aabb),
...this.subnode[2].getPointsInRegion(aabb),
...this.subnode[3].getPointsInRegion(aabb),
];
}
}
class QuadTree {
constructor(width, height) {
this.root = new QTNode(0, 0, width, height);
}
insert(point) {
return this.root.insert(point);
}
closest(point) {
const getLeaf = (point, node) => {
if (!node.aabb.contains(point)) return null;
if (node.type == QTNode.Empty ||
node.type == QTNode.Leaf) return node;
for (let subnode of node.subnode) {
const leaf = getLeaf(point, subnode);
if (leaf !== null) return leaf;
}
return null;
}
const leaf = getLeaf(point, this.root);
if (leaf === null) return leaf;
const dim = 2*Math.max(leaf.aabb.width, leaf.aabb.height);
const region = new AABB(point.x - dim, point.y - dim, 2*dim, 2*dim);
const points = this.root.getPointsInRegion(region);
let closest = null;
let min_dist = 100 * this.root.aabb.width * this.root.aabb.height;
const dist = (a, b) => (a.x - b.x)**2 + (a.y - b.y)**2;
for (let pt of points) {
const d = dist(point, pt);
if (d < min_dist) {
closest = pt;
min_dist = d;
}
}
return closest;
}
}
export { AABB, QTNode, QuadTree };
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