After watching Philipp Kindermann's excellent sweep-line videos I think I finally understand how this algorithm works.
This is my humble take on an implementation of the segment line intersection sweep-line algorithm.
The library crate also contains a line intersection function.
This crate is educational, not ready for any production purpose. It has been adopted as a cgmath library here.
Interactive step-by-step example:
fish
cargo run --example fltk_gui --features console_trace
Intersection function API example: ```rust use intersect2d::{intersect, Intersection};
let line1 = geo::Line::
let rv = intersect(&line1, &line2); match rv { Some(Intersection::Intersection(_a)) => panic!("expected an overlap"), Some(Intersection::OverLap(a)) => println!("{:?}", a), None => panic!("expected an overlap"), } // you can also get a single intersection point from the Intersection enum. // Albeit geometrically incorrect, it makes things easy println!("{:?}", rv.unwrap().single()); ```
Sweep-line API example:
rust
let lines = vec![
geo::Line::<f64>::from([(200.0,200.),(350.0,300.)]),
geo::Line::<f64>::from([(400.0,200.),(250.0,300.)]),
];
let results = intersect2d::algorithm::AlgorithmData::<f64>::default()
.with_ignore_end_point_intersections(false)?
.with_lines(lines.into_iter())?
.compute()?;
for (point, line) in results {
println!("Intersection @{:?} Involved lines:{:?}", point, line);
}
Detection of self-intersecting geo::LineString:
```rust
let coordinates = vec![(200., 200.), (300., 300.), (400., 200.), (200., 300.)];
let line_string = geo::LineString::
// Obviously this example only makes sense for LinesStrings with many points.
// A simple brute force O(n²) intersection test will be faster than this O(nlog(n)+k)
// sweep-line algorithm if n is small enough.
let result = intersect2d::algorithm::AlgorithmData::
or using the `SelfIntersectingExclusive` trait:
rust
// SelfIntersectingExclusive does not report endpoint intersections
use intersect2d::SelfIntersectingExclusive;
let coordinates = vec![(200., 200.), (300., 300.), (400., 200.), (200., 300.)]; let line_string = geo::LineString::from(coordinates);
if linestring.isself_intersecting()? { println!("Intersection detected"); }
for intersections in linestring.selfintersections()? { println!("Intersection: {:?}", intersections); } ```
You can also check a bunch of geo::Line for self intersections using the SelfIntersectingInclusive trait:
rust
// SelfIntersectingInclusive reports endpoint intersections
use intersect2d::SelfIntersectingInclusive;
let lines = vec![
geo::Line::<f64>::from([(200.0,200.),(350.0,300.)]),
geo::Line::<f64>::from([(400.0,200.),(250.0,300.)]),
];
if lines.is_self_intersecting_inclusive()? {
println!("Intersection detected");
}
for intersections in lines.self_intersections_inclusive()? {
println!("Intersection: {:?}", intersections);
}