fix precision error on voronoi.neighbors (#138)

Co-authored-by: Mike Bostock <mbostock@gmail.com>
d3 · Mar 4, 2023 · 9caef5c · 9caef5c
1 parent 2196b80
commit 9caef5c
Show file tree

Hide file tree

Showing 2 changed files with 12 additions and 11 deletions.
diff --git a/src/voronoi.js b/src/voronoi.js
@@ -152,17 +152,17 @@ 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 (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]
-          ) {
+          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) {
             yield j;
             break loop;
           }

diff --git a/test/voronoi-test.js b/test/voronoi-test.js
@@ -53,12 +53,7 @@ it("zero-length edges are removed", () => {
 
 it("voronoi neighbors are clipped", () => {
    const voronoi = Delaunay.from([[300, 10], [200, 100], [300, 100], [10, 10], [350, 200], [350, 400]]).voronoi([0, 0, 500, 150]);
-   assert.deepStrictEqual([...voronoi.neighbors(0)].sort(), [1, 2]);
-   assert.deepStrictEqual([...voronoi.neighbors(1)].sort(), [0, 2]);
-   assert.deepStrictEqual([...voronoi.neighbors(2)].sort(), [0, 1, 4]);
-   assert.deepStrictEqual([...voronoi.neighbors(3)].sort(), []);
-   assert.deepStrictEqual([...voronoi.neighbors(4)].sort(), [2]);
-   assert.deepStrictEqual([...voronoi.neighbors(5)].sort(), []);
+   assert.deepStrictEqual([0, 1, 2, 3, 4, 5].map(i => [...voronoi.neighbors(i)].sort()), [ [1, 2], [0, 2, 3], [0, 1, 4], [1], [2], []]);
 });
 
 it("unnecessary points on the corners are avoided (#88)", () => {
@@ -87,3 +82,9 @@ it("cellPolygons filter out empty cells and have the cell index as a property",
     Object.assign([[0, 1], [1, 0], [2, 0], [2, 2], [0, 2], [0, 1]], { index: 2 })
   ]);
 });
+
+it("voronoi.neighbors returns the correct neighbors", () => {
+  const points = [[10, 10], [36, 27], [90, 19], [50, 75]];
+  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]]);
+});