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use super::{point_in_rect, Intersects};
use crate::kernels::*;
use crate::*;
impl<T> Intersects<Coord<T>> for Line<T>
where
T: GeoNum,
{
fn intersects(&self, rhs: &Coord<T>) -> bool {
// First we check if the point is collinear with the line.
T::Ker::orient2d(self.start, self.end, *rhs) == Orientation::Collinear
// In addition, the point must have _both_ coordinates
// within the start and end bounds.
&& point_in_rect(*rhs, self.start, self.end)
}
}
symmetric_intersects_impl!(Coord<T>, Line<T>);
symmetric_intersects_impl!(Line<T>, Point<T>);
impl<T> Intersects<Line<T>> for Line<T>
where
T: GeoNum,
{
fn intersects(&self, line: &Line<T>) -> bool {
// Special case: self is equiv. to a point.
if self.start == self.end {
return line.intersects(&self.start);
}
// Precondition: start and end are distinct.
// Check if orientation of rhs.{start,end} are different
// with respect to self.{start,end}.
let check_1_1 = T::Ker::orient2d(self.start, self.end, line.start);
let check_1_2 = T::Ker::orient2d(self.start, self.end, line.end);
if check_1_1 != check_1_2 {
// Since the checks are different,
// rhs.{start,end} are distinct, and rhs is not
// collinear with self. Thus, there is exactly
// one point on the infinite extensions of rhs,
// that is collinear with self.
// By continuity, this point is not on the
// exterior of rhs. Now, check the same with
// self, rhs swapped.
let check_2_1 = T::Ker::orient2d(line.start, line.end, self.start);
let check_2_2 = T::Ker::orient2d(line.start, line.end, self.end);
// By similar argument, there is (exactly) one
// point on self, collinear with rhs. Thus,
// those two have to be same, and lies (interior
// or boundary, but not exterior) on both lines.
check_2_1 != check_2_2
} else if check_1_1 == Orientation::Collinear {
// Special case: collinear line segments.
// Equivalent to 4 point-line intersection
// checks, but removes the calls to the kernel
// predicates.
point_in_rect(line.start, self.start, self.end)
|| point_in_rect(line.end, self.start, self.end)
|| point_in_rect(self.end, line.start, line.end)
|| point_in_rect(self.end, line.start, line.end)
} else {
false
}
}
}