glam

A simple and fast 3D math library for games and graphics.

Development status

glam is in beta stage. Base functionality has been implemented and the look and feel of the API has solidified.

Features

• f32 types
  • vectors: Vec2, Vec3, Vec3A and Vec4
  • square matrices: Mat2, Mat3, Mat3A and Mat4
  • a quaternion type: Quat
  • affine transformation types: Affine2 and Affine3A
• f64 types
  • vectors: DVec2, DVec3 and DVec4
  • square matrices: DMat2, DMat3 and DMat4
  • a quaternion type: DQuat
  • affine transformation types: DAffine2 and DAffine3
• i32 types
  • vectors: IVec2, IVec3 and IVec4
• u32 types
  • vectors: UVec2, UVec3 and UVec4
• bool types
  • vectors: BVec2, BVec3 and BVec4

SIMD

The Vec3A, Vec4, Quat, Mat2, Mat3A, Mat4, Affine2 and Affine3A types use 128-bit wide SIMD vector types for storage on x86, x86_64 and wasm32 architectures. As a result, these types are all 16 byte aligned and depending on the size of the type or the type's members, they may contain internal padding. This results in some wasted space in the cases of Vec3A, Mat3A, Affine2 and Affine3A. However, the use of SIMD generally results in better performance than scalar math.

glam outperforms similar Rust libraries for common operations as tested by the mathbench project.

Enabling SIMD

SIMD is supported on x86, x86_64 and wasm32 targets.

• SSE2 is enabled by default on x86_64 targets.
• To enable SSE2 on x86 targets add -C target-feature=+sse2 to RUSTCFLAGS.
• To enable simd128 on wasm32 targets add -C target-feature=+simd128 to RUSTFLAGS.

Note that SIMD on wasm32 passes tests but has not been benchmarked, performance may or may not be better than scalar math.

no_std support

no_std support can be enabled by compiling with --no-default-features to disable std support and --features libm for math functions that are only defined in std. For example:

[dependencies]
glam = { version = "0.20.4", default-features = false, features = ["libm"] }

To support both std and no_std builds in project, you can use the following in your Cargo.toml:

[features]
default = ["std"]

std = ["glam/std"]
libm = ["glam/libm"]

[dependencies]
glam = { version = "0.20.4", default-features = false }

Optional features

• approx - traits and macros for approximate float comparisons
• bytemuck - for casting into slices of bytes
• libm - required to compile with no_std
• mint - for interoperating with other 3D math libraries
• num-traits - required to compile no_std, will be included when enabling the libm feature
• rand - implementations of Distribution trait for all glam types.
• serde - implementations of Serialize and Deserialize for all glam types. Note that serialization should work between builds of glam with and without SIMD enabled
• rkyv - implementations of Archive, Serialize and Deserialize for all glam types. Note that serialization is not interoperable with and without the scalar-math feature. It should work between all other builds of glam. Endian conversion is currently not supported
• bytecheck - to perform archive validation when using the rkyv feature
• [fast-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.

Feature gates

• scalar-math - compiles with SIMD support disabled
• 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 validation assertions to all builds
• cuda - forces glam types to match expected cuda alignment

Minimum Supported Rust Version (MSRV)

The minimum supported version of Rust for glam is 1.52.1.

wasm32 SIMD intrinsics require Rust 1.54.0.

Conventions

Column vectors

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, e.g. v' = Mv. DirectX uses row vectors, OpenGL uses column vectors. There are pros and cons to both.

Column-major order

Matrices are stored in column major format. Each column vector is stored in contiguous memory.

Co-ordinate system

glam is co-ordinate system agnostic and intends to support both right-handed and left-handed conventions.

Design Philosophy

The design of this library is guided by a desire for simplicity and good performance.

• No generics and minimal traits in the public API for simplicity of usage
• All dependencies are optional (e.g. mint, rand and serde)
• Follows the Rust API Guidelines where possible
• Aiming for 100% test coverage
• Common functionality is benchmarked using Criterion.rs

Architecture

See ARCHITECTURE.md for details on glam's internals.

Inspirations

There were many inspirations for the interface and internals of glam from the Rust and C++ worlds. In particular:

• How to write a maths library in 2016 inspired the initial Vec3A implementation
• Realtime Math - header only C++11 with SSE and NEON SIMD intrinsic support
• DirectXMath - header only SIMD C++ linear algebra library for use in games and graphics apps
• glam is a play on the name of the popular C++ library GLM

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Contributions in any form (issues, pull requests, etc.) to this project must adhere to Rust's Code of Conduct.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Thank you to all of the glam contributors!

Support

If you are interested in contributing or have a request or suggestion start a discussion on GitHub. See CONTRIBUTING.md for more information for contributors.

The Game Development in Rust Discord and Bevy Engine Discord servers are not official support channels but can be good places to ask for help with glam.

Attribution

glam contains code ported from the following C++ libraries:

• DirectXMath - MIT License - Copyright (c) 2011-2020 Microsoft Corp
• Realtime Math - MIT License - Copyright (c) 2018 Nicholas Frechette
• GLM - MIT License - Copyright (c) 2005 - G-Truc Creation

See ATTRIBUTION.md for details.