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Fix point-linestring intersection #500

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merged 2 commits into from
Aug 21, 2020
Merged

Fix point-linestring intersection #500

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a8a95e5
Harmonize point-line intersection algorithms
urschrei Aug 21, 2020
b130f59
Fix point-linestring containment algorithm
urschrei Aug 21, 2020
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39 changes: 30 additions & 9 deletions geo-types/src/private_utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -143,15 +143,36 @@ where
return true;
}
for line in line_string.lines() {
if ((line.start.y == line.end.y)
&& (line.start.y == point.y())
&& (point.x() > line.start.x.min(line.end.x))
&& (point.x() < line.start.x.max(line.end.x)))
|| ((line.start.x == line.end.x)
&& (line.start.x == point.x())
&& (point.y() > line.start.y.min(line.end.y))
&& (point.y() < line.start.y.max(line.end.y)))
{
// This is a duplicate of the line-contains-point logic in the "intersects" module
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ah yes, great shame be on us all.

These algorithms exist in geo-types so we can have a nice rstar integration, right?

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Yep, although as we have now discovered they can easily get out of whack and cause problems, so I'd love to find some better way of providing the functionality, although the reason it's done like this is to avoid circular dependencies 😩

let tx = if line.dx() == T::zero() {
None
} else {
Some((point.x() - line.start.x) / line.dx())
};
let ty = if line.dy() == T::zero() {
None
} else {
Some((point.y() - line.start.y) / line.dy())
};
let contains = match (tx, ty) {
(None, None) => {
// Degenerate line
point.0 == line.start
}
(Some(t), None) => {
// Horizontal line
point.y() == line.start.y && T::zero() <= t && t <= T::one()
}
(None, Some(t)) => {
// Vertical line
point.x() == line.start.x && T::zero() <= t && t <= T::one()
}
(Some(t_x), Some(t_y)) => {
// All other lines
(t_x - t_y).abs() <= T::epsilon() && T::zero() <= t_x && t_x <= T::one()
}
};
if contains {
return true;
}
}
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11 changes: 10 additions & 1 deletion geo/src/algorithm/contains.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -141,7 +141,7 @@ where
T: Float,
{
fn contains(&self, p: &Point<T>) -> bool {
::geo_types::private_utils::line_string_contains_point(self, *p)
self.lines().any(|line| line.contains(p))
}
}

Expand Down Expand Up @@ -439,6 +439,15 @@ mod test {
use crate::algorithm::contains::Contains;
use crate::line_string;
use crate::{Coordinate, Line, LineString, MultiPolygon, Point, Polygon, Rect, Triangle};


#[test]
// see https://github.com/georust/geo/issues/452
fn linestring_contains_point() {
let line_string = LineString::from(vec![(0., 0.), (3., 3.)]);
let point_on_line = Point::new(1., 1.);
assert!(line_string.contains(&point_on_line));
}
#[test]
// V doesn't contain rect because two of its edges intersect with V's exterior boundary
fn polygon_does_not_contain_polygon() {
Expand Down