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intersectPoints fails to find intersections #342

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dpthurst opened this issue Aug 27, 2019 · 3 comments
Open

intersectPoints fails to find intersections #342

dpthurst opened this issue Aug 27, 2019 · 3 comments
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@dpthurst
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I have an examples where 'intersectPoints' unaccountably fails to find an intersection point that must exist by the Jordan Curve Theorem. I've attached an example with two explicit paths.
bug.zip

Geometrically, this is a circle around a certain point and a horizontal path leading from the center to a point outside the circle. Apologies for the explicit coordinates, this is extracted from a hyperbolic geometry drawing. The issue seems to be sensitive to the size of the circle.

@byorgey
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byorgey commented Aug 30, 2019

Thanks for the report. I wonder if this is a similar issue to #142 .

@byorgey byorgey added the bug label Aug 30, 2019
@dpthurst
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dpthurst commented Sep 1, 2019

That does sound like a very similar issue, that was my guess as to what was happening. The intersection point algorithm needs to account for the line being continuous.

@georgefst
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I've hit this a few times myself, though mine perhaps looks less like an example of #142.

A runnable example, plus SVG output, can be found in this gist.

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