Handle line segments intersecting at their endpoints. The algorithm I - #378
Handle line segments intersecting at their endpoints. The algorithm I#378dabreegster wants to merge 1 commit into
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ported ages ago doesn't handle this, and somehow I didn't notice until b2519e3.
michaelkirk
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michaelkirk
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- /// Undefined if the two lines have more than one intersection point Is there a clear behavior for collinear lines now?
It seems like in the case that their endpoints overlap we have clear behavior, but what if their overlap is more than a point?
| if self.pt1() == other.pt2() { | ||
| return Some(self.pt1()); | ||
| } | ||
| if self.pt2() == other.pt1() { |
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equality is reflexive, so this one check is redundant ( the subsequent p2 == p2 check should stay though)
Oh, hmm... you mean the lines (0.0, 0.0) -> (1.0, 1.0) and (2.0, 2.0) -> (1.0, 1.0)? Those indeed are collinear. Does their code not work with collinear lines or something? |
It returns collinear in this case, but I'd expect just the endpoint (1, 1). Maybe it depends if the line segment endpoints are open or closed; the docs use
I'll add some more tests and figure out how to implement. I would expect |
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I mentioned this in Slack, but depending on how urgent this is I'm hoping the |
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I might hold off on this, then -- thanks! No rush; not planning to work on intersection geometry anytime soon again |
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ported ages ago doesn't handle this, and somehow I didn't notice until
b2519e3.
@michaelkirk, any thoughts on this incremental improvement? I wanted to take this opportunity to rely on a better tested library for line segment intersection, but all I found was https://crates.io/crates/line_intersection. I gave it a shot at https://github.com/dabreegster/abstreet/blob/21eb14ba52afd549f0d6d0732ec3fe405a19869e/geom/src/line.rs#L75, but it said the line segments in the unit test were co-linear, which doesn't seem correct to me.
I'll keep looking around for ways to reduce the core code in
geom. Ideally it'd mostly just wrap other crates that're better tested.