Function point_in_poly2d

pub fn point_in_poly2d(pt: &Point2<f32>, poly: &[Point2<f32>]) -> bool

Tests if the given point is inside an arbitrary closed polygon with arbitrary orientation, using a winding number algorithm.

This function works with both convex and concave polygons, and even self-intersecting polygons. It uses a winding number algorithm to determine if a point is inside.

The polygon is assumed to be closed, i.e., first and last point of the polygon are implicitly assumed to be connected by an edge.

This handles concave polygons. For a faster function dedicated to convex polygons, see point_in_convex_poly2d.

Arguments

• pt - The point to test
• poly - A slice of points defining the polygon vertices in order (clockwise or counter-clockwise)

Returns

true if the point is inside the polygon, false otherwise.

Examples

Convex Polygon (Square)

use parry2d::utils::point_in_poly2d;
use parry2d::na::Point2;

let square = vec![
    Point2::origin(),
    Point2::new(2.0, 0.0),
    Point2::new(2.0, 2.0),
    Point2::new(0.0, 2.0),
];

let inside = Point2::new(1.0, 1.0);
let outside = Point2::new(3.0, 1.0);

assert!(point_in_poly2d(&inside, &square));
assert!(!point_in_poly2d(&outside, &square));

Concave Polygon (L-Shape)

use parry2d::utils::point_in_poly2d;
use parry2d::na::Point2;

// L-shaped polygon (concave)
let l_shape = vec![
    Point2::origin(),
    Point2::new(2.0, 0.0),
    Point2::new(2.0, 1.0),
    Point2::new(1.0, 1.0),
    Point2::new(1.0, 2.0),
    Point2::new(0.0, 2.0),
];

let inside_corner = Point2::new(0.5, 0.5);
let outside_corner = Point2::new(1.5, 1.5);

assert!(point_in_poly2d(&inside_corner, &l_shape));
assert!(!point_in_poly2d(&outside_corner, &l_shape));

Complex Polygon with Holes

use parry2d::utils::point_in_poly2d;
use parry2d::na::Point2;

// A star shape (self-intersecting creates a complex winding pattern)
let star = vec![
    Point2::new(0.0, 1.0),
    Point2::new(0.5, 0.5),
    Point2::new(1.0, 1.0),
    Point2::new(0.7, 0.3),
    Point2::new(1.0, -0.5),
    Point2::origin(),
    Point2::new(-1.0, -0.5),
    Point2::new(-0.7, 0.3),
    Point2::new(-1.0, 1.0),
    Point2::new(-0.5, 0.5),
];

let center = Point2::new(0.0, 0.5);
assert!(point_in_poly2d(&center, &star));

Empty Polygon

use parry2d::utils::point_in_poly2d;
use parry2d::na::Point2;

let empty: Vec<Point2<f32>> = vec![];
let point = Point2::new(1.0, 1.0);

// An empty polygon contains no points
assert!(!point_in_poly2d(&point, &empty));