Line-line intersection edge cases #3396
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There's still an issue with coincident lines which don't share a start or end point. |
Tests/misc/bezierTools_test.py
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| pt = lineLineIntersections(*seg1, *seg2)[0][0] | ||
| assert pt == (250.0, 1000.0) | ||
| seg3 = [(250, 810), (250, 500)] | ||
| assert lineLineIntersections(*seg1, *seg3) == [] |
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Don't seg1 and seg3 intersect at (250, 810)?
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oh sorry I see now (was typing from mobile), the segments actually are coincident, sitting on top of one another. In theory they intersect in all the points where they overlap, but since we need to return some finite results it's ok to return [] in this edge case
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wait I'm still confused... I think you swapped the two cases.
all the three segments above seg1, seg2 and seg3 are parallel to one another and the Y axis, have the same x coordinate 250; seg1 and and seg2 are the ones that overlap one another, they also share the starting point but coincide for the entire length of seg1 (which is a subset of seg2). So I'd expect we would return [] in this case. Whereas you are returning (250.0, 1000.0) which is their starting point.
On the other hand, seg1 and seg2, while being parallel (x coordinates are all 250), they only touch where seg1 ends and seg3 starts, i.e. (250, 810) -- so I would expect the latter to be returned as their intersection, not []
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Literally edge cases, this deals with intersections on coincident lines.