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 
13 use crate::vector::Vector2F;
14 use pathfinder_simd::default::F32x2;
15 
16 #[derive(Clone, Copy, Debug)]
17 pub struct UnitVector(pub Vector2F);
18 
19 impl UnitVector {
20     #[inline]
from_angle(theta: f32) -> UnitVector21     pub fn from_angle(theta: f32) -> UnitVector {
22         UnitVector(Vector2F::new(theta.cos(), theta.sin()))
23     }
24 
25     /// Angle addition formula.
26     #[inline]
rotate_by(&self, other: UnitVector) -> UnitVector27     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]
rev_rotate_by(&self, other: UnitVector) -> UnitVector34     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]
halve_angle(&self) -> UnitVector41     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