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//! Contains functions and structures to help with operations on polygons.
pub mod polygon_graph;
pub mod triangulate;
pub use polygon_graph::*;
pub use triangulate::*;
use super::Vec2;
use nalgebra::{ClosedDiv, ClosedMul, ClosedSub, RealField, Scalar};
use num_traits::Zero;
use std::ops::Neg;
#[derive(Debug)]
// TODO: Support polygons with holes
pub struct Polygon<T: Scalar + Copy> {
pub corners: Vec<Vec2<T>>,
}
impl<T: Scalar + Copy> Polygon<T> {
pub fn new(corners: Vec<Vec2<T>>) -> Self {
Self { corners }
}
/// Check whether a point is inside a polygon or not. If a point lies on an edge, it also
/// counts as inside the polygon.
pub fn contains_point(&self, p: Vec2<T>) -> bool
where
T: Zero + ClosedSub + ClosedMul + ClosedDiv + Neg<Output = T> + PartialOrd,
{
let n = self.corners.len();
let a = self.corners[n - 1];
let mut b = self.corners[n - 2];
let mut ax;
let mut ay = a.y - p.y;
let mut bx = b.x - p.x;
let mut by = b.y - p.y;
let mut lup = by > ay;
for i in 0..n {
// ax = bx;
ay = by;
b = self.corners[i];
bx = b.x - p.x;
by = b.y - p.y;
if ay == by {
continue;
}
lup = by > ay;
}
let mut depth = 0;
for i in 0..n {
ax = bx;
ay = by;
let b = &self.corners[i];
bx = b.x - p.x;
by = b.y - p.y;
if ay < T::zero() && by < T::zero() {
// both "up" or both "down"
continue;
}
if ay > T::zero() && by > T::zero() {
// both "up" or both "down"
continue;
}
if ax < T::zero() && bx < T::zero() {
// both points on the left
continue;
}
if ay == by && (if ax < bx { ax } else { bx }) <= T::zero() {
return true;
}
if ay == by {
continue;
}
let lx = ax + (((bx - ax) * -ay) / (by - ay));
if lx == T::zero() {
// point on edge
return true;
}
if lx > T::zero() {
depth += 1;
}
if ay == T::zero() && lup && by > ay {
// hit vertex, both up
depth -= 1;
}
if ay == T::zero() && !lup && by < ay {
// hit vertex, both down
depth -= 1;
}
lup = by > ay;
}
(depth & 1) == 1
}
/// Join this polygon with another, ensuring the area of the two stays the same, but the
/// overlap is not doubled, but instead joined into one.
/// Returns the Polygons themselves, if there is no overlap
pub fn unite(self, other: Polygon<T>) -> Vec<Polygon<T>>
where
T: RealField,
{
let mut graph = PolygonGraph::from_polygon(&self);
graph.add_all(&other);
// TODO: Make bounding box support multiple polygons
vec![graph.bounding_polygon()]
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn polygon_contains() {
let polygon = Polygon::new(vec![
Vec2::new(0., 0.),
Vec2::new(-1., 1.),
Vec2::new(0., 2.),
Vec2::new(1., 3.),
Vec2::new(3., 1.5),
Vec2::new(2., 0.),
Vec2::new(1., 1.),
]);
assert!(!polygon.contains_point(Vec2::new(1., -2.)));
assert!(!polygon.contains_point(Vec2::new(-1., 0.5)));
assert!(polygon.contains_point(Vec2::new(0., 0.5)));
assert!(polygon.contains_point(Vec2::new(0.5, 1.)));
assert!(polygon.contains_point(Vec2::new(0.5, 1.5)));
assert!(!polygon.contains_point(Vec2::new(-2., 1.9)));
assert!(!polygon.contains_point(Vec2::new(0., 3.)));
assert!(polygon.contains_point(Vec2::new(1., 3.)));
}
#[test]
fn polygon_union() {
let first = Polygon::new(vec![
Vec2::new(-2., 1.),
Vec2::new(-0.5, 2.5),
Vec2::new(2., 2.),
Vec2::new(0.5, 1.5),
Vec2::new(1., 0.),
Vec2::new(-0.5, 1.),
]);
let second = Polygon::new(vec![
Vec2::new(0., 0.),
Vec2::new(-2., 2.),
Vec2::new(3., 2.),
Vec2::new(1.5, 0.),
]);
let union = first.unite(second);
assert_eq!(union.len(), 1);
let union = &union[0];
println!("Union of the two polygons: {:?}", union);
assert_eq!(union.corners.len(), 11);
assert!(union
.corners
.iter()
.find(|&p| p.x == 0. && p.y == 0.)
.is_some());
}
}
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