Broken voronoi #119
Comments
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The problem comes from https://github.com/d3/d3-delaunay/blob/master/src/voronoi.js#L43 ; if we don't add the 1e8 factor here everything is solved. It breaks a few tests though, which I'll have to inspect more closely, in particular https://github.com/d3/d3-delaunay/blob/master/test/voronoi-test.js#L75 is problmatic since the voronoi that we test for is patently wrong (note: the strange point is a double point where only the last digit of a coordinate changes). Reference commit for that test: 4cf3466 |
…te triangles created by points of the hull that are almost exactly aligned. The "circumcenter" of such a triangle is a point at the infinite, in the direction orthogonal to the hull. It must also be "away from the center". But we can't rely on the sign of *ab*, since it's itself a difference of two products and can be of the wrong sign, leading to a ray that sometimes goes in the opposite direction. To overcome this problem, we use the first point of the first triangle as a guide to tell us which way is "away from the center".
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I came across what I believe is the same bug: https://observablehq.com/@plmrry/voronoi-bug My hacky fix is to add |
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Yes, thanks for the example. I've checked and branch #120 fixes it too. We just need a bit of time to publish it because it's a major version change. |
* upgrade to testing branch delaunator v5 * The issue #119 comes from the circumcenters we assign to the degenerate triangles created by points of the hull that are almost exactly aligned. The "circumcenter" of such a triangle is a point at the infinite, in the direction orthogonal to the hull. It must also be "away from the center". But we can't rely on the sign of *ab*, since it's itself a difference of two products and can be of the wrong sign, leading to a ray that sometimes goes in the opposite direction. To overcome this problem, we use the first point of the first triangle as a guide to tell us which way is "away from the center". * delaunator v5 * Minor change: Only compute bl and cl when needed. #125 * Subtle out of bounds checking need documenting * Minor: _ClipFinit() Prevent the propagation of undefined. * Adopt type=module follow changes in d3-format: * type=module * add exports * remove zip * update dependencies * readme: type=module * Update README.md Co-authored-by: Mike Bostock <mbostock@gmail.com> * update README: legacy env. * remove esm devDependency * strictEqual, deepStrictEqual (@aulonm) * Update src/voronoi.js Co-authored-by: Mike Bostock <mbostock@gmail.com> * delaunay.renderPoints(r) closes #130 * simpler check, more tests * more tests * space * Update src/delaunay.js Co-authored-by: Mike Bostock <mbostock@gmail.com> * test renderPoints(context, null) gives r=2 * remove Sublime project * update dependencies * stricter eslint * cleaner imports * fix copyright Co-authored-by: Martin <martinfrances107@hotmail.com> Co-authored-by: Mike Bostock <mbostock@gmail.com>
Test case at mapbox/delaunator#68
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