use quadtree to speed up curve intersection checks
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Skyler Lehmkuhl
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e0c5e13f57
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7ba51940ae
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class Quadtree {
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constructor(boundary, capacity) {
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// Boundary is the bounding box of the area this quadtree node covers
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// Capacity is the maximum number of curves a node can hold before subdividing
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this.boundary = boundary; // {x: {min: <value>, max: <value>}, y: {min: <value>, max: <value>}}
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this.capacity = capacity;
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this.curveIndexes = [];
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this.curves = [];
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this.divided = false;
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this.nw = null; // Northwest quadrant
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this.ne = null; // Northeast quadrant
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this.sw = null; // Southwest quadrant
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this.se = null; // Southeast quadrant
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}
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// Check if a bounding box intersects with the boundary of this quadtree node
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intersects(bbox) {
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return !(bbox.x.max < this.boundary.x.min || bbox.x.min > this.boundary.x.max ||
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bbox.y.max < this.boundary.y.min || bbox.y.min > this.boundary.y.max);
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}
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// Subdivide this quadtree node into 4 quadrants
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subdivide() {
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const xMid = (this.boundary.x.min + this.boundary.x.max) / 2;
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const yMid = (this.boundary.y.min + this.boundary.y.max) / 2;
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const nwBoundary = { x: { min: this.boundary.x.min, max: xMid }, y: { min: this.boundary.y.min, max: yMid }};
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const neBoundary = { x: { min: xMid, max: this.boundary.x.max }, y: { min: this.boundary.y.min, max: yMid }};
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const swBoundary = { x: { min: this.boundary.x.min, max: xMid }, y: { min: yMid, max: this.boundary.y.max }};
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const seBoundary = { x: { min: xMid, max: this.boundary.x.max }, y: { min: yMid, max: this.boundary.y.max }};
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this.nw = new Quadtree(nwBoundary, this.capacity);
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this.ne = new Quadtree(neBoundary, this.capacity);
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this.sw = new Quadtree(swBoundary, this.capacity);
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this.se = new Quadtree(seBoundary, this.capacity);
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this.divided = true;
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}
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insert (curve, curveIdx) {
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const bbox = curve.bbox()
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if (!this.intersects(curve.bbox())) {
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let newNode = new Quadtree(this.boundary, this.capacity)
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newNode.curveIndexes = this.curveIndexes;
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newNode.curves = this.curves;
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newNode.divided = this.divided;
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newNode.nw = this.nw;
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newNode.ne = this.ne;
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newNode.sw = this.sw;
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newNode.se = this.se;
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this.curveIndexes = [];
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this.curves = [];
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this.subdivide()
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if (bbox.x.max < this.boundary.x.max) {
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if (bbox.y.max < this.boundary.y.max) {
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this.boundary.x.min -= this.boundary.x.max - this.boundary.x.min
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this.boundary.y.min -= this.boundary.y.max - this.boundary.y.min
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this.nw = newNode
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} else {
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this.boundary.x.min -= this.boundary.x.max - this.boundary.x.min
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this.boundary.y.max += this.boundary.y.max - this.boundary.y.min
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this.sw = newNode
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}
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} else {
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if (bbox.y.max < this.boundary.y.max) {
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this.boundary.x.max += this.boundary.x.max - this.boundary.x.min
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this.boundary.y.min -= this.boundary.y.max - this.boundary.y.min
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this.ne = newNode
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} else {
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this.boundary.x.max += this.boundary.x.max - this.boundary.x.min
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this.boundary.y.max += this.boundary.y.max - this.boundary.y.min
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this.se = newNode
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}
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}
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return this.insert(curve, curveIdx)
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} else {
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return this._insert(curve, curveIdx)
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}
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}
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// Insert a curve into the quadtree, subdividing if necessary
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_insert(curve, curveIdx) {
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// If the curve's bounding box doesn't intersect this node's boundary, do nothing
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if (!this.intersects(curve.bbox())) {
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return false;
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}
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// If the node has space, insert the curve here
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if (this.curves.length < this.capacity) {
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this.curves.push(curve);
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this.curveIndexes.push(curveIdx)
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return true;
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}
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// Otherwise, subdivide and insert the curve into the appropriate quadrant
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if (!this.divided) {
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this.subdivide();
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}
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return (
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this.nw._insert(curve, curveIdx) ||
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this.ne._insert(curve, curveIdx) ||
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this.sw._insert(curve, curveIdx) ||
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this.se._insert(curve, curveIdx)
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);
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}
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// Query all curves that intersect with a given bounding box
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query(range, found = []) {
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// If the range doesn't intersect with this node's boundary, return
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if (!this.intersects(range)) {
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return found;
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}
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// Check the curves in this node
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for (let i = 0; i < this.curves.length; i++) {
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if (this.bboxIntersect(this.curves[i].bbox(), range)) {
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found.push(this.curveIndexes[i]); // Return the curve index instead of the curve
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}
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}
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// If the node is subdivided, check the child quadrants
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if (this.divided) {
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this.nw.query(range, found);
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this.ne.query(range, found);
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this.sw.query(range, found);
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this.se.query(range, found);
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}
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return found;
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}
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// Helper method to check if two bounding boxes intersect
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bboxIntersect(bbox1, bbox2) {
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return !(bbox1.x.max < bbox2.x.min || bbox1.x.min > bbox2.x.max ||
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bbox1.y.max < bbox2.y.min || bbox1.y.min > bbox2.y.max);
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}
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clear() {
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this.curveIndexes = [];
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this.curves = [];
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this.divided = false;
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this.nw = null; // Northwest quadrant
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this.ne = null; // Northeast quadrant
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this.sw = null; // Southwest quadrant
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this.se = null; // Southeast quadrant
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}
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draw(ctx) {
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// Debug visualization
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ctx.save()
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ctx.strokeStyle = "red"
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ctx.lineWidth = 1
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ctx.beginPath()
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ctx.rect(
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this.boundary.x.min,
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this.boundary.y.min,
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this.boundary.x.max-this.boundary.x.min,
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this.boundary.y.max-this.boundary.y.min
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)
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ctx.stroke()
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if (this.divided) {
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this.nw.draw(ctx)
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this.ne.draw(ctx)
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this.sw.draw(ctx)
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this.se.draw(ctx)
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}
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ctx.restore()
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}
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}
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export { Quadtree };
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