[−][src]Crate glam

glam

glam is a simple and fast linear algebra library for games and graphics.

Features

glam is built with SIMD in mind. Currently only SSE2 on x86/x86_64 is supported as this is what stable Rust supports.

Single precision float f32 support only (for now)
SSE2 storage and optimization for many types, including Mat2, Mat4, Quat, Vec3A and Vec4
Scalar fallback implementations exist when SSE2 is not available
Most functionality includes unit tests and benchmarks

Linear algebra conventions

glam interprets vectors as column matrices (also known as "column vectors") meaning when transforming a vector with a matrix the matrix goes on the left.

use glam::{Mat3, Vec3};
let m = Mat3::identity();
let x = Vec3::unit_x();
let v = m * x;
assert_eq!(v, x);

Matrices are stored in memory in column-major order.

Size and alignment of types

Some glam types use SIMD for storage meaning they are 16 byte aligned, these types include Mat2, Mat4, Quat, Vec3A and Vec4.

When SSE2 is not available on the target architecture this type will still be 16 byte aligned so that object sizes and layouts will not change between architectures.

SIMD support can be disabled entirely using the scalar-math feature. This feature will also disable SIMD alignment meaning most types will use native f32 alignment of 4 bytes.

All the main glam types are #[repr(C)], so they are possible to expose as struct members to C interfaces if desired. Be mindful of Vec3A's extra padding though.

Vec3A

Vec3A is a SIMD optimized version of the Vec3 type, which due to 16 byte alignment results in Vec3A containing 4 bytes of padding making it 16 bytes in size in total.

Type	`f32` bytes	Align bytes	Padding	Size bytes
`Vec3`	12	4	0	12
`Vec3A`	12	16	4	16

Despite this wasted space the SIMD version tends to outperform the f32 implementation in mathbench benchmarks.

glam treats Vec3 as the default vector 3 type and Vec3A a special case for optimization. When methods need to return a vector 3 type they will generally return Vec3.

There are From trait implementations for converting from Vec4 to a Vec3A and between Vec3 and Vec3A (and vice versa).

use glam::{Vec3, Vec3A, Vec4};

let v4 = Vec4::new(1.0, 2.0, 3.0, 4.0);

// Convert from `Vec4` to `Vec3A`, this is a no-op if SIMD is supported.
let v3a = Vec3A::from(v4);
assert_eq!(Vec3A::new(1.0, 2.0, 3.0), v3a);

// Convert from `Vec3A` to `Vec3`.
let v3 = Vec3::from(v3a);
assert_eq!(Vec3::new(1.0, 2.0, 3.0), v3);

// Convert from `Vec3` to `Vec3A`.
let v3a = Vec3A::from(v3);
assert_eq!(Vec3A::new(1.0, 2.0, 3.0), v3a);

Vector swizzles

glam vector types have functions allowing elements of vectors to be reordered, this includes creating a vector of a different size from the vectors elements.

The swizzle functions are implemented using traits to add them to each vector type. This is primarily because there are a lot of swizzle functions which can obfuscate the other vector functions in documentation and so on. The traits are Vec2Swizzles, Vec3Swizzles, Vec3ASwizzles and Vec4Swizzles.

Note that Vec2Swizzles, Vec3Swizzles and Vec4Swizzles will return a Vec3 type for 3 element swizzles. Vec3ASwizzles will return a Vec3A for 3 element swizzles.

use glam::{swizzles::*, Vec2, Vec3, Vec3A, Vec4};

let v = Vec4::new(1.0, 2.0, 3.0, 4.0);

// Reverse elements of `v`, if SIMD is supported this will use a vector shuffle.
let wzyx = v.wzyx();
assert_eq!(Vec4::new(4.0, 3.0, 2.0, 1.0), wzyx);

// Swizzle the yzw elements of `v` into a `Vec3`
let yzw = v.yzw();
assert_eq!(Vec3::new(2.0, 3.0, 4.0), yzw);

// To swizzle a `Vec4` into a `Vec3A` swizzle the `Vec4` first then convert to
// `Vec3A`. If SIMD is supported this will use a vector shuffle. The last
// element of the shuffled `Vec4` is ignored by the `Vec3A`.
let yzw = Vec3A::from(v.yzwx());
assert_eq!(Vec3A::new(2.0, 3.0, 4.0), yzw);

// You can swizzle from a `Vec4` to a `Vec2`
let xy = v.xy();
assert_eq!(Vec2::new(1.0, 2.0), xy);

// And back again
let yyxx = xy.yyxx();
assert_eq!(Vec4::new(2.0, 2.0, 1.0, 1.0), yyxx);

SIMD and scalar consistency

glam types implement serde Serialize and Deserialize traits to ensure that they will serialize and deserialize exactly the same whether or not SIMD support is being used.

The SIMD versions implement the core::fmt::Debug and core::fmt::Display traits so they print the same as the scalar version.

use glam::Vec4;
let a = Vec4::new(1.0, 2.0, 3.0, 4.0);
assert_eq!(format!("{}", a), "[1, 2, 3, 4]");

Feature gates

All glam dependencies are optional, however some are required for tests and benchmarks.

std - the default feature, has no dependencies.
rand - used to generate random values. Used in benchmarks.
serde - used for serialization and deserialization of types.
mint - used for interoperating with other linear algebra libraries.
scalar-math - disables SIMD support and uses native alignment for all types.
debug-glam-assert - adds assertions in debug builds which check the validity of parameters passed to glam to help catch runtime errors.
glam-assert - adds assertions to all builds which check the validity of parameters passed to glam to help catch runtime errors.

const_mat2	Creates a `Mat2` from two column vectors that can be used to initialize a constant value.
const_mat3	Creates a `Mat3` from three column vectors that can be used to initialize a constant value.
const_mat4	Creates a `Mat4` from four column vectors that can be used to initialize a constant value.
const_quat	Creates a `Quat` from `x`, `y`, `z` and `w` values that can be used to initialize a constant value.
const_vec2	Creates a `Vec2` that can be used to initialize a constant value.
const_vec3	Creates a `Vec3` that can be used to initialize a constant value.
const_vec3a	Creates a `Vec3A` that can be used to initialize a constant value.
const_vec4	Creates a `Vec4` that can be used to initialize a constant value.

Structs

Mat2	A 2x2 column major matrix.
Mat3	A 3x3 column major matrix.
Mat4	A 4x4 column major matrix.
Quat	A quaternion representing an orientation.
Vec2	A 2-dimensional vector.
Vec2Mask	A 2-dimensional vector mask.
Vec3	A 3-dimensional vector without SIMD support.
Vec3A	A 3-dimensional vector with SIMD support.
Vec3AMask	A 3-dimensional vector mask.
Vec3Mask	A 3-dimensional vector mask.
Vec4	A 4-dimensional vector.
Vec4Mask	A 4-dimensional vector mask.

Traits

Vec2Swizzles
Vec3ASwizzles
Vec3Swizzles
Vec4Swizzles

Functions

mat2	Creates a `Mat2` from two column vectors.
mat3	Creates a `Mat3` from three column vectors.
mat4	Creates a `Mat4` from four column vectors.
quat	Creates a `Quat` from `x`, `y`, `z` and `w` values.
vec2	Creates a `Vec2`.
vec3	Creates a `Vec3`.
vec3a	Creates a `Vec3`.
vec4	Creates a `Vec4`.