Expand description
§glam
glam
is a simple and fast linear algebra library for games and graphics.
§Features
§SIMD
glam
is built with SIMD in mind. Many f32
types use 128-bit SIMD vector types for storage
and/or implementation. The use of SIMD generally enables better performance than using primitive
numeric types such as f32
.
Some glam
types use SIMD for storage meaning they are 16 byte aligned, these types include
Mat2
, Mat3A
, Mat4
, Quat
, Vec3A
, Vec4
, Affine2
an Affine3A
. Types
with an A
suffix are a SIMD alternative to a scalar type, e.g. Vec3
uses f32
storage and
Vec3A
uses SIMD storage.
When SIMD is not available on the target the types will maintain 16 byte alignment and internal padding so that object sizes and layouts will not change between architectures. There are scalar math fallback implementations exist when SIMD is not available. It is intended to add support for other SIMD architectures once they appear in stable Rust.
Currently only SSE2 on x86/x86_64 is supported as this is what stable Rust supports.
§Vec3A and Mat3A
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. Mat3A
is composed
of three Vec3A
columns.
Despite this wasted space the SIMD implementations tend to outperform f32
implementations in
mathbench benchmarks.
glam
treats Vec3
as the default 3D vector type and Vec3A
a special case for optimization.
When methods need to return a 3D vector 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);
§Affine2 and Affine3A
Affine2
and Affine3A
are composed of a linear transform matrix and a vector translation. The
represent 2D and 3D affine transformations which are commonly used in games.
The table below shows the performance advantage of Affine2
over Mat3A
and Mat3A
over Mat3
.
operation | Mat3 | Mat3A | Affine2 |
---|---|---|---|
inverse | 11.4±0.09ns | 7.1±0.09ns | 5.4±0.06ns |
mul self | 10.5±0.04ns | 5.2±0.05ns | 4.0±0.05ns |
transform point2 | 2.7±0.02ns | 2.7±0.03ns | 2.8±0.04ns |
transform vector2 | 2.6±0.01ns | 2.6±0.03ns | 2.3±0.02ns |
Performance is much closer between Mat4
and Affine3A
with the affine type being faster to
invert.
operation | Mat4 | Affine3A |
---|---|---|
inverse | 15.9±0.11ns | 10.8±0.06ns |
mul self | 7.3±0.05ns | 7.0±0.06ns |
transform point3 | 3.6±0.02ns | 4.3±0.04ns |
transform point3a | 3.0±0.02ns | 3.0±0.04ns |
transform vector3 | 4.1±0.02ns | 3.9±0.04ns |
transform vector3a | 2.8±0.02ns | 2.8±0.02ns |
Benchmarks were taken on an Intel Core i7-4710HQ.
§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::X;
let v = m * x;
assert_eq!(v, x);
Matrices are stored in memory in column-major order.
All angles are in radians. Rust provides the f32::to_radians()
and f64::to_radians()
methods to
convert from degrees.
§Direct element access
Because some types may internally be implemented using SIMD types, direct access to vector elements
is supported by implementing the Deref
and DerefMut
traits.
use glam::Vec3A;
let mut v = Vec3A::new(1.0, 2.0, 3.0);
assert_eq!(3.0, v.z);
v.z += 1.0;
assert_eq!(4.0, v.z);
§glam assertions
glam
does not enforce validity checks on method parameters at runtime. For example methods that
require normalized vectors as input such as Quat::from_axis_angle(axis, angle)
will not check
that axis is a valid normalized vector. To help catch unintended misuse of glam
the
debug-glam-assert
or glam-assert
features can be enabled to add checks ensure that inputs to
are valid.
§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
and
Vec4Swizzles
.
Note that the Vec3Swizzles
implementation for Vec3A
will return a Vec3A
for 3 element
swizzles, all other implementations will return Vec3
.
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.approx
- traits and macros for approximate float comparisonsbytemuck
- for casting into slices of byteslibm
- useslibm
math functions instead ofstd
, required to compile withno_std
mint
- for interoperating with other 3D math librariesrand
- implementations ofDistribution
trait for allglam
types.rkyv
- implementations ofArchive
,Serialize
andDeserialize
for allglam
types. Note that serialization is not interoperable with and without thescalar-math
feature. It should work between all other builds ofglam
. Endian conversion is currently not supportedbytecheck
- to perform archive validation when using therkyv
featureserde
- implementations ofSerialize
andDeserialize
for allglam
types. Note that serialization should work between builds ofglam
with and without SIMD enabledscalar-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 toglam
to help catch runtime errors.glam-assert
- adds assertions to all builds which check the validity of parameters passed toglam
to help catch runtime errors.cuda
- forcesglam
types to match expected cuda alignmentfast-math
- By default, glam attempts to provide bit-for-bit identical results on all platforms. Using this feature will enable platform specific optimizations that may not be identical to other platforms. Intermediate libraries should not use this feature and defer the decision to the final binary build.core-simd
- enables SIMD support via the portable simd module. This is an unstable feature which requires a nightly Rust toolchain andstd
support.
§Minimum Supported Rust Version (MSRV)
The minimum supported Rust version is 1.68.2
.
Re-exports§
pub use self::swizzles::Vec2Swizzles;
pub use self::swizzles::Vec3Swizzles;
pub use self::swizzles::Vec4Swizzles;
pub use self::bool::*;
pub use self::f32::*;
pub use self::f64::*;
pub use self::i16::*;
pub use self::u16::*;
pub use self::i32::*;
pub use self::u32::*;
pub use self::i64::*;
pub use self::u64::*;
Modules§
bool
vector mask types.f32
vector, quaternion and matrix types.f64
vector, quaternion and matrix types.i16
vector types.i32
vector types.i64
vector types.- Traits adding swizzle methods to all vector types.
u16
vector types.u32
vector types.u64
vector types.
Enums§
- Rotation Helper Euler rotation sequences.