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use crate::{coord, CoordFloat, CoordsIter, Polygon, Triangle};
/// Triangulate polygons using an [ear-cutting algorithm](https://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf).
pub trait TriangulateEarcut<T: CoordFloat> {
/// # Examples
///
/// ```
/// use geo::{coord, polygon, Triangle, TriangulateEarcut};
///
/// let square_polygon = polygon![
/// (x: 0., y: 0.), // SW
/// (x: 10., y: 0.), // SE
/// (x: 10., y: 10.), // NE
/// (x: 0., y: 10.), // NW
/// (x: 0., y: 0.), // SW
/// ];
///
/// let triangles = square_polygon.earcut_triangles();
///
/// assert_eq!(
/// vec![
/// Triangle(
/// coord! { x: 0., y: 10. }, // NW
/// coord! { x: 10., y: 10. }, // NE
/// coord! { x: 10., y: 0. }, // SE
/// ),
/// Triangle(
/// coord! { x: 10., y: 0. }, // SE
/// coord! { x: 0., y: 0. }, // SW
/// coord! { x: 0., y: 10. }, // NW
/// ),
/// ],
/// triangles,
/// );
/// ```
fn earcut_triangles(&self) -> Vec<Triangle<T>> {
self.earcut_triangles_iter().collect()
}
/// # Examples
///
/// ```
/// use geo::{coord, polygon, Triangle, TriangulateEarcut};
///
/// let square_polygon = polygon![
/// (x: 0., y: 0.), // SW
/// (x: 10., y: 0.), // SE
/// (x: 10., y: 10.), // NE
/// (x: 0., y: 10.), // NW
/// (x: 0., y: 0.), // SW
/// ];
///
/// let mut triangles_iter = square_polygon.earcut_triangles_iter();
///
/// assert_eq!(
/// Some(Triangle(
/// coord! { x: 0., y: 10. }, // NW
/// coord! { x: 10., y: 10. }, // NE
/// coord! { x: 10., y: 0. }, // SE
/// )),
/// triangles_iter.next(),
/// );
///
/// assert_eq!(
/// Some(Triangle(
/// coord! { x: 10., y: 0. }, // SE
/// coord! { x: 0., y: 0. }, // SW
/// coord! { x: 0., y: 10. }, // NW
/// )),
/// triangles_iter.next(),
/// );
///
/// assert!(triangles_iter.next().is_none());
/// ```
fn earcut_triangles_iter(&self) -> Iter<T> {
Iter(self.earcut_triangles_raw())
}
/// Return the raw result from the `earcutr` library: a one-dimensional vector of polygon
/// vertices (in XY order), and the indices of the triangles within the vertices vector. This
/// method is less ergonomic than the `earcut_triangles` and `earcut_triangles_iter`
/// methods, but can be helpful when working in graphics contexts that expect flat vectors of
/// data.
///
/// # Examples
///
/// ```
/// use geo::{coord, polygon, Triangle, TriangulateEarcut};
/// use geo::triangulate_earcut::RawTriangulation;
///
/// let square_polygon = polygon![
/// (x: 0., y: 0.), // SW
/// (x: 10., y: 0.), // SE
/// (x: 10., y: 10.), // NE
/// (x: 0., y: 10.), // NW
/// (x: 0., y: 0.), // SW
/// ];
///
/// let mut triangles_raw = square_polygon.earcut_triangles_raw();
///
/// assert_eq!(
/// RawTriangulation {
/// vertices: vec![
/// 0., 0., // SW
/// 10., 0., // SE
/// 10., 10., // NE
/// 0., 10., // NW
/// 0., 0., // SW
/// ],
/// triangle_indices: vec![
/// 3, 0, 1, // NW-SW-SE
/// 1, 2, 3, // SE-NE-NW
/// ],
/// },
/// triangles_raw,
/// );
/// ```
fn earcut_triangles_raw(&self) -> RawTriangulation<T>;
}
impl<T: CoordFloat> TriangulateEarcut<T> for Polygon<T> {
fn earcut_triangles_raw(&self) -> RawTriangulation<T> {
let input = polygon_to_earcutr_input(self);
let triangle_indices =
earcutr::earcut(&input.vertices, &input.interior_indexes, 2).unwrap();
RawTriangulation {
vertices: input.vertices,
triangle_indices,
}
}
}
/// The raw result of triangulating a polygon from `earcutr`.
#[derive(Debug, PartialEq, Clone)]
pub struct RawTriangulation<T: CoordFloat> {
/// Flattened one-dimensional vector of polygon vertices (in XY order).
pub vertices: Vec<T>,
/// Indices of the triangles within the vertices vector.
pub triangle_indices: Vec<usize>,
}
#[derive(Debug)]
pub struct Iter<T: CoordFloat>(RawTriangulation<T>);
impl<T: CoordFloat> Iterator for Iter<T> {
type Item = Triangle<T>;
fn next(&mut self) -> Option<Self::Item> {
let triangle_index_1 = self.0.triangle_indices.pop()?;
let triangle_index_2 = self.0.triangle_indices.pop()?;
let triangle_index_3 = self.0.triangle_indices.pop()?;
Some(Triangle(
self.triangle_index_to_coord(triangle_index_1),
self.triangle_index_to_coord(triangle_index_2),
self.triangle_index_to_coord(triangle_index_3),
))
}
}
impl<T: CoordFloat> Iter<T> {
fn triangle_index_to_coord(&self, triangle_index: usize) -> crate::Coord<T> {
coord! {
x: self.0.vertices[triangle_index * 2],
y: self.0.vertices[triangle_index * 2 + 1],
}
}
}
struct EarcutrInput<T: CoordFloat> {
pub vertices: Vec<T>,
pub interior_indexes: Vec<usize>,
}
fn polygon_to_earcutr_input<T: CoordFloat>(polygon: &crate::Polygon<T>) -> EarcutrInput<T> {
let mut vertices = Vec::with_capacity(polygon.coords_count() * 2);
let mut interior_indexes = Vec::with_capacity(polygon.interiors().len());
debug_assert!(polygon.exterior().0.len() >= 4);
flat_line_string_coords_2(polygon.exterior(), &mut vertices);
for interior in polygon.interiors() {
debug_assert!(interior.0.len() >= 4);
interior_indexes.push(vertices.len() / 2);
flat_line_string_coords_2(interior, &mut vertices);
}
EarcutrInput {
vertices,
interior_indexes,
}
}
fn flat_line_string_coords_2<T: CoordFloat>(
line_string: &crate::LineString<T>,
vertices: &mut Vec<T>,
) {
for coord in &line_string.0 {
vertices.push(coord.x);
vertices.push(coord.y);
}
}
#[cfg(test)]
mod test {
use super::TriangulateEarcut;
use crate::{coord, polygon, Triangle};
#[test]
fn test_triangle() {
let triangle_polygon = polygon![
(x: 0., y: 0.),
(x: 10., y: 0.),
(x: 10., y: 10.),
(x: 0., y: 0.),
];
let triangles = triangle_polygon.earcut_triangles();
assert_eq!(
&[Triangle(
coord! { x: 10.0, y: 0.0 },
coord! { x: 0.0, y: 0.0 },
coord! { x: 10.0, y: 10.0 },
),][..],
triangles,
);
}
#[test]
fn test_square() {
let square_polygon = polygon![
(x: 0., y: 0.),
(x: 10., y: 0.),
(x: 10., y: 10.),
(x: 0., y: 10.),
(x: 0., y: 0.),
];
let mut triangles = square_polygon.earcut_triangles();
triangles.sort_by(|t1, t2| t1.1.x.partial_cmp(&t2.2.x).unwrap());
assert_eq!(
&[
Triangle(
coord! { x: 10.0, y: 0.0 },
coord! { x: 0.0, y: 0.0 },
coord! { x: 0.0, y: 10.0 },
),
Triangle(
coord! { x: 0.0, y: 10.0 },
coord! { x: 10.0, y: 10.0 },
coord! { x: 10.0, y: 0.0 },
),
][..],
triangles,
);
}
}