Vectors, quaternions, and matrices for general purposes, and computer graphics.

Vector, matrix, and quaternion data structures and operations. Uses f32 or f64 based types.

Example use cases:

• Computer graphics
• Biomechanics
• Robotics and unmanned aerial vehicles.
• Structural chemistry and biochemistry
• Cosmology modeling
• Various scientific and engineering applications
• Aircraft attitude systems and autopilots

Vector and Quaternion types are copy.

For Compatibility with no_std targets, e.g. embedded, disable default features, and enable the no_std feature. This omits std::fmt::Display implementations, and enables num_traits's libm capabilities for certain operations. lin_alg = { version = "^1.1.0", default-features = false, features = ["no_std"] }

For computer-graphics functionality (e.g. specialty matrix constructors, and [de]serialization to byte arrays for passing to and from GPUs), use the computer_graphics feature. For bincode binary encoding and decoding, use the encode feature.

For information on practical quaternion operations: Quaternions: A practical guide.

The From trait is implemented for most types, for converting between f32 and f64 variants using the into() syntax.

SIMD

Includes WIP SIMD constructs (SoA layout): The Vec3S,Vec4S, and QuaternionS types. They are configured with 256-bit wide (AVX) values, performing (for vectors) operations on 8 f32 Vec3 or Vec4s, or 4 f64 ones. See the example below for details. not all functionality is implemented, and only f32 variants are implemented at this time.

Various operator overloads are implemented. For example, you can (scalar) multiply a Vec3S by a f32, a [f32; 8], or a __m256. This applies to quaternion operations, like multiplication, as well.

Examples

See the official documentation (Linked above) for details. Below is a brief, impractical syntax overview:

use core::f32::consts::TAU;

use lin_alg::f32::{Vec3, Quaternion};

fn main() {
    let _ = Vec3::new_zero();
    
    let a = Vec3::new(1., 1., 1.);
    let b = Vec3::new(0., -1., 10.);
    
    let mut c = a + b;
    
    let d = a.dot(b);
    
    c.normalize(); // or:
    let e = c.to_normalized();
    
    let f = a.cross(b);
    
    let g = Quaternion::from_unit_vecs(d, e);
    
    let h = g.inverse();
    
    let k = Quaternion::new_identity();
    
    let l = k.rotate_vec(c);
    
    l.magnitude();
    
    let m = Quaternion::from_axis_angle(Vec3::new(1., 0., 0.), TAU / 16.);
}

If using for computer graphics, this functionality may be helpful:

    let a = Vec3::new(1., 1., 1.);
    let bytes = a.to_bytes(); // Send this to the GPU. `Quaternion` and `MatN` have similar methods.

    let model_mat = Mat4::new_translation(self.position)
        * self.orientation.to_matrix()
        * Mat4::new_scaler_partial(self.scale);

    let proj_mat = Mat4::new_perspective_lh(self.fov_y, self.aspect, self.near, self.far);

    let view_mat = self.orientation.inverse().to_matrix() * Mat4::new_translation(-self.position);

    // Example of rolling a camera around the forward axis:
    let fwd = orientation.rotate_vec(FWD_VEC);
    let rotation = Quaternion::from_axis_angle(fwd, -rotate_key_amt);
    orientation = rotation * orientation;

A practical geometry example:

/// Calculate the dihedral angle between 4 positions (3 bonds).
/// The `bonds` are one atom's position, substracted from the next. Order matters.
pub fn calc_dihedral_angle(bond_middle: Vec3, bond_adjacent1: Vec3, bond_adjacent2: Vec3) -> f64 {
    // Project the next and previous bonds onto the plane that has this bond as its normal.
    // Re-normalize after projecting.
    let bond1_on_plane = bond_adjacent1.project_to_plane(bond_middle).to_normalized();
    let bond2_on_plane = bond_adjacent2.project_to_plane(bond_middle).to_normalized();

    // Not sure why we need to offset by 𝜏/2 here, but it seems to be the case
    let result = bond1_on_plane.dot(bond2_on_plane).acos() + TAU / 2.;

    // The dot product approach to angles between vectors only covers half of possible
    // rotations; use a determinant of the 3 vectors as matrix columns to determine if what we
    // need to modify is on the second half.
    let det = det_from_cols(bond1_on_plane, bond2_on_plane, bond_middle);

    if det < 0. { result } else { TAU - result }
}

A SIMD example over vector operations:

use lin_alg::f32:{Vec3, Vec3S};

// Non-SIMD Vec3s we'll start with.
let vec_a = Vec3::new(1., 2., 3.);
let vec_b = Vec3::new(4., 5., 6.);

// An example where we copy the same Vec3 into all 8 slots. In most practical uses,
// each slot will contain a different value.
let a = Vec3S::new([vec_a; 8]);
let b = Vec3S::new([vec_b; 8]);

// Perform vector addition on 8 Vec3s at once.
let c = a + b;

// Create a [Vec3; 8], due to the `unpack` method.
let d = a.cross(b).unpack();

// Create a `__m256`, then convert to an array.
let dot_result: [f32; 8] = unsafe { transmute(a.dot(b)) };

// Create a [f32; 8].
let dot_result = a.dot_unpack(b);

let e = vec_a * 3.;
let f = vec_a * [3.; 8];
let g = vec_a * _mm256_set1_ps(3.);

A SIMD example of rotating vectors.

use core::f32::consts::TAU;
use lin_alg::f32::{Quaternion, Vec3, QuaternionS, Vec3S};

let rot_init = [
    Quaternion::from_unit_vecs(UP, FORWARD),
    Quaternion::from_unit_vecs(UP, -FORWARD),
    Quaternion::from_unit_vecs(UP, RIGHT),
    Quaternion::from_unit_vecs(UP, -RIGHT),
    Quaternion::from_unit_vecs(UP, UP),
    Quaternion::from_unit_vecs(UP, -UP),
    Quaternion::from_axis_angle(RIGHT, TAU/4.),
    Quaternion::from_axis_angle(RIGHT, TAU/8.),
];

let rotation = QuaternionS::new(rot_init);

// This could be 8 separate values.
let vec = Vec3S::new([UP; 8]);

let result = rotation.rotate_vec(vec).unpack();

let sqrt_2_div_2 = 2_f32.sqrt()/2.;
let angled = Vec3::new(0., -sqrt_2_div_2, sqrt_2_div_2);

assert!((result[0] - FORWARD).magnitude() < f32::EPSILON);
assert!((result[1] - -FORWARD).magnitude() < f32::EPSILON);
assert!((result[2] - RIGHT).magnitude() < f32::EPSILON);
assert!((result[3] - -RIGHT).magnitude() < f32::EPSILON);
assert!((result[4] - UP).magnitude() < f32::EPSILON);
assert!((result[5] - -UP).magnitude() < f32::EPSILON);
assert!((result[6] - -FORWARD).magnitude() < f32::EPSILON);
assert!((result[7] - angled).magnitude() < f32::EPSILON);