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robust intercept #139

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merged 4 commits into from
Mar 7, 2023
Merged

robust intercept #139

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e06078c
intercept
Fil Mar 5, 2023
b2466b1
robust intercept
Fil Mar 5, 2023
fa1b634
_intercept is not needed; we can use c0 and c1 to order; more tests
Fil Mar 7, 2023
87f41ad
strict equality, prettier
mbostock Mar 7, 2023
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14 changes: 8 additions & 6 deletions src/voronoi.js
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Expand Up @@ -152,17 +152,16 @@ export default class Voronoi {
return this.delaunay._step(i, x, y) === i;
}
*neighbors(i) {
const epsilon = 1e-12;
const ci = this._clip(i);
if (ci) for (const j of this.delaunay.neighbors(i)) {
const cj = this._clip(j);
// find the common edge
if (cj) loop: for (let ai = 0, li = ci.length; ai < li; ai += 2) {
for (let aj = 0, lj = cj.length; aj < lj; aj += 2) {
if (Math.abs(ci[ai] - cj[aj]) < epsilon
&& Math.abs(ci[ai + 1] - cj[aj + 1]) < epsilon
&& Math.abs(ci[(ai + 2) % li] - cj[(aj + lj - 2) % lj]) < epsilon
&& Math.abs(ci[(ai + 3) % li] - cj[(aj + lj - 1) % lj]) < epsilon) {
if (ci[ai] === cj[aj]
&& ci[ai + 1] === cj[aj + 1]
&& ci[(ai + 2) % li] === cj[(aj + lj - 2) % lj]
&& ci[(ai + 3) % li] === cj[(aj + lj - 1) % lj]) {
yield j;
break loop;
}
Expand Down Expand Up @@ -239,8 +238,11 @@ export default class Voronoi {
return P;
}
_clipSegment(x0, y0, x1, y1, c0, c1) {
// for more robustness, always consider the segment in the same order
const flip = c0 < c1;
if (flip) [x0, y0, x1, y1, c0, c1] = [x1, y1, x0, y0, c1, c0];
while (true) {
if (c0 === 0 && c1 === 0) return [x0, y0, x1, y1];
if (c0 === 0 && c1 === 0) return flip ? [x1, y1, x0, y0] : [x0, y0, x1, y1];
if (c0 & c1) return null;
let x, y, c = c0 || c1;
if (c & 0b1000) x = x0 + (x1 - x0) * (this.ymax - y0) / (y1 - y0), y = this.ymax;
Expand Down
18 changes: 18 additions & 0 deletions test/voronoi-test.js
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Expand Up @@ -88,3 +88,21 @@ it("voronoi.neighbors returns the correct neighbors", () => {
const voronoi = Delaunay.from(points).voronoi([0, 0, 100, 90]);
assert.deepStrictEqual([0, 1, 2, 3].map(i => [...voronoi.neighbors(i)].sort()), [[1], [0, 2, 3], [1, 3], [1, 2]]);
});

it("voronoi.neighbors returns the correct neighbors, flipped vertically", () => {
const points = [[10, -10], [36, -27], [90, -19], [50, -75]];
const voronoi = Delaunay.from(points).voronoi([0, -90, 100, 0]);
assert.deepStrictEqual([0, 1, 2, 3].map(i => [...voronoi.neighbors(i)].sort()), [[1], [0, 2, 3], [1, 3], [1, 2]]);
});

it("voronoi.neighbors returns the correct neighbors, flipped horizontally", () => {
const points = [[-10, 10], [-36, 27], [-90, 19], [-50, 75]];
const voronoi = Delaunay.from(points).voronoi([-100, 0, 0, 90]);
assert.deepStrictEqual([0, 1, 2, 3].map(i => [...voronoi.neighbors(i)].sort()), [[1], [0, 2, 3], [1, 3], [1, 2]]);
});

it("voronoi.neighbors returns the correct neighbors, rotated", () => {
const points = [[-10, -10], [-36, -27], [-90, -19], [-50, -75]];
const voronoi = Delaunay.from(points).voronoi([-100, -90, 0, 0]);
assert.deepStrictEqual([0, 1, 2, 3].map(i => [...voronoi.neighbors(i)].sort()), [[1], [0, 2, 3], [1, 3], [1, 2]]);
});