2017-09-19 00:00:34 -04:00
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// pathfinder/path-utils/src/line.rs
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//
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// Copyright © 2017 The Pathfinder Project Developers.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Geometry utilities for straight line segments.
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2017-09-25 22:15:36 -04:00
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use euclid::approxeq::ApproxEq;
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2017-10-04 14:06:41 -04:00
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use euclid::{Point2D, Vector2D, Vector3D};
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2017-09-20 19:18:55 -04:00
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2017-09-25 18:58:00 -04:00
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use intersection::Intersect;
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2017-09-19 00:00:34 -04:00
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2017-09-25 18:58:00 -04:00
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#[derive(Clone, Copy, PartialEq, Debug)]
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2017-09-19 00:00:34 -04:00
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pub struct Line {
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pub endpoints: [Point2D<f32>; 2],
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}
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impl Line {
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#[inline]
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pub fn new(endpoint_0: &Point2D<f32>, endpoint_1: &Point2D<f32>) -> Line {
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Line {
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endpoints: [*endpoint_0, *endpoint_1],
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}
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}
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#[inline]
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pub fn sample(&self, t: f32) -> Point2D<f32> {
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self.endpoints[0].lerp(self.endpoints[1], t)
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}
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2017-09-20 19:18:55 -04:00
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2017-09-25 22:15:36 -04:00
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#[inline]
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pub fn solve_t_for_x(&self, x: f32) -> f32 {
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let x_span = self.endpoints[1].x - self.endpoints[0].x;
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if x_span != 0.0 {
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(x - self.endpoints[0].x) / x_span
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} else {
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0.0
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}
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}
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#[inline]
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pub fn solve_y_for_x(&self, x: f32) -> f32 {
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self.sample(self.solve_t_for_x(x)).y
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}
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#[inline]
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pub fn subdivide(&self, t: f32) -> (Line, Line) {
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let midpoint = self.sample(t);
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(Line::new(&self.endpoints[0], &midpoint), Line::new(&midpoint, &self.endpoints[1]))
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}
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pub fn subdivide_at_x(&self, x: f32) -> (Line, Line) {
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let (prev_part, next_part) = self.subdivide(self.solve_t_for_x(x));
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if self.endpoints[0].x <= self.endpoints[1].x {
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(prev_part, next_part)
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} else {
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(next_part, prev_part)
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}
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}
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2017-09-21 21:57:48 -04:00
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#[inline]
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pub fn side(&self, point: &Point2D<f32>) -> f32 {
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self.to_vector().cross(*point - self.endpoints[0])
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}
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2017-09-20 19:18:55 -04:00
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#[inline]
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pub(crate) fn to_vector(&self) -> Vector2D<f32> {
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self.endpoints[1] - self.endpoints[0]
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}
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#[inline]
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pub fn intersect<T>(&self, other: &T) -> Option<Point2D<f32>> where T: Intersect {
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<Line as Intersect>::intersect(self, other)
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}
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2017-09-25 22:15:36 -04:00
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/// A faster version of `intersect` for the special case of two lines.
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///
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/// https://stackoverflow.com/a/565282
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pub fn intersect_with_line(&self, other: &Line) -> Option<Point2D<f32>> {
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let (p, r) = (self.endpoints[0], self.to_vector());
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let (q, s) = (self.endpoints[1], other.to_vector());
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let rs = r.cross(s);
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if rs.approx_eq(&0.0) {
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return None
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}
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let t = (q - p).cross(s) / rs;
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if t < f32::approx_epsilon() || t > 1.0f32 - f32::approx_epsilon() {
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return None
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}
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let u = (q - p).cross(r) / rs;
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if u < f32::approx_epsilon() || u > 1.0f32 - f32::approx_epsilon() {
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return None
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}
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Some(p + r * t)
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}
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2017-10-04 14:06:41 -04:00
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/// A version of `intersect` that accounts for intersection points at infinity.
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///
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/// See Sederberg § 7.2.1.
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pub fn intersect_at_infinity(&self, other: &Line) -> Option<Point2D<f32>> {
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let this_vector_0 = Vector3D::new(self.endpoints[0].x, self.endpoints[0].y, 1.0);
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let this_vector_1 = Vector3D::new(self.endpoints[1].x, self.endpoints[1].y, 1.0);
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let other_vector_0 = Vector3D::new(other.endpoints[0].x, other.endpoints[0].y, 1.0);
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let other_vector_1 = Vector3D::new(other.endpoints[1].x, other.endpoints[1].y, 1.0);
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let this_vector = this_vector_0.cross(this_vector_1);
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let other_vector = other_vector_0.cross(other_vector_1);
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let intersection = this_vector.cross(other_vector);
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if intersection.z.approx_eq(&0.0) {
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None
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} else {
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Some(Point2D::new(intersection.x / intersection.z, intersection.y / intersection.z))
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}
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}
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// Translates this line in the perpendicular counterclockwise direction by the given length.
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pub(crate) fn offset(&self, length: f32) -> Line {
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let vector = self.to_vector();
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let normal = Vector2D::new(-vector.y, vector.x).normalize() * length;
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Line::new(&(self.endpoints[0] + normal), &(self.endpoints[1] + normal))
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}
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2017-09-19 00:00:34 -04:00
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}
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