71 lines
1.7 KiB
JavaScript
71 lines
1.7 KiB
JavaScript
import Quad from "./quad.js";
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export default function(x, y, radius) {
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var data,
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x0 = this._x0,
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y0 = this._y0,
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x1,
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y1,
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x2,
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y2,
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x3 = this._x1,
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y3 = this._y1,
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quads = [],
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node = this._root,
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q,
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i;
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if (node) quads.push(new Quad(node, x0, y0, x3, y3));
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if (radius == null) radius = Infinity;
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else {
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x0 = x - radius, y0 = y - radius;
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x3 = x + radius, y3 = y + radius;
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radius *= radius;
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}
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while (q = quads.pop()) {
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// Stop searching if this quadrant can’t contain a closer node.
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if (!(node = q.node)
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|| (x1 = q.x0) > x3
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|| (y1 = q.y0) > y3
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|| (x2 = q.x1) < x0
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|| (y2 = q.y1) < y0) continue;
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// Bisect the current quadrant.
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if (node.length) {
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var xm = (x1 + x2) / 2,
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ym = (y1 + y2) / 2;
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quads.push(
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new Quad(node[3], xm, ym, x2, y2),
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new Quad(node[2], x1, ym, xm, y2),
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new Quad(node[1], xm, y1, x2, ym),
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new Quad(node[0], x1, y1, xm, ym)
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);
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// Visit the closest quadrant first.
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if (i = (y >= ym) << 1 | (x >= xm)) {
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q = quads[quads.length - 1];
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quads[quads.length - 1] = quads[quads.length - 1 - i];
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quads[quads.length - 1 - i] = q;
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}
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}
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// Visit this point. (Visiting coincident points isn’t necessary!)
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else {
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var dx = x - +this._x.call(null, node.data),
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dy = y - +this._y.call(null, node.data),
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d2 = dx * dx + dy * dy;
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if (d2 < radius) {
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var d = Math.sqrt(radius = d2);
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x0 = x - d, y0 = y - d;
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x3 = x + d, y3 = y + d;
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data = node.data;
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}
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}
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}
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return data;
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}
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