1// pathfinder/geometry/src/unit_vector.rs
2//
3// Copyright © 2019 The Pathfinder Project Developers.
4//
5// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8// option. This file may not be copied, modified, or distributed
9// except according to those terms.
10
11//! A utility module that allows unit vectors to be treated like angles.
12
13use crate::vector::Vector2F;
14use pathfinder_simd::default::F32x2;
15
16#[derive(Clone, Copy, Debug)]
17pub struct UnitVector(pub Vector2F);
18
19impl UnitVector {
20 #[inline]
21 pub fn from_angle(theta: f32) -> UnitVector {
22 UnitVector(Vector2F::new(theta.cos(), theta.sin()))
23 }
24
25 /// Angle addition formula.
26 #[inline]
27 pub fn rotate_by(&self, other: UnitVector) -> UnitVector {
28 let products = (self.0).0.to_f32x4().xyyx() * (other.0).0.to_f32x4().xyxy();
29 UnitVector(Vector2F::new(products[0] - products[1], products[2] + products[3]))
30 }
31
32 /// Angle subtraction formula.
33 #[inline]
34 pub fn rev_rotate_by(&self, other: UnitVector) -> UnitVector {
35 let products = (self.0).0.to_f32x4().xyyx() * (other.0).0.to_f32x4().xyxy();
36 UnitVector(Vector2F::new(products[0] + products[1], products[2] - products[3]))
37 }
38
39 /// Half angle formula.
40 #[inline]
41 pub fn halve_angle(&self) -> UnitVector {
42 let x = self.0.x();
43 let term = F32x2::new(x, -x);
44 UnitVector(Vector2F((F32x2::splat(0.5) * (F32x2::splat(1.0) + term)).max(F32x2::default())
45 .sqrt()))
46 }
47}
48