glam

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

Development status

glam is in a alpha stage. Minimal base functionality has been implemented and the look and feel of the API has solidified.

Features

• Only single precision floating point (f32) arithmetic is supported
• vectors: Vec3, Vec3, Vec4
• square matrices: Mat2, Mat3, Mat4
• a quaternion type: Quat
• an angle type: Angle
• SSE2 opimized sin_cos

SIMD

The Vec3, Vec4 and Quat types use SSE2 on x86/x86_64 architectures. Mat3 and Mat4 also use SSE2 for some functionality such as inverse and transpose. Not everything has a SIMD implementation yet.

Note that this does result in some wasted space in the case of Vec3 and Mat3 as the SIMD vector type is 16 bytes large and 16 byte aligned.

glam outperforms similar Rust libraries such as cgmath and nalgebra-glm for common operations as tested by the mathbench project.

If you are more concerned with size than speed you can build glam with the feature scalar-math enabled to disable SIMD usage.

The Vec2 and Mat2 types do not have a SIMD implemenation. Mat2 may benefit from a SIMD impelemtation in the future.

Due to the use of SIMD, vector elements may only be get and set via accessor methods, e.g. Vec3::x() and Vec3::set_x(). If getting or setting more than one element it is more efficient to convert from tuples or arrays:

let (x, y, z) = v.into();

Default features

• approx - implementations of the AbsDiffEq and UlpsEq traits for all glam types. This is primarily used for unit testing.
• mint - for interoperating with other 3D math libraries
• rand - implementations of Distribution trait for all glam types. This is primarily used for unit testing.
• serde - implementations of Serialize and Deserialize for all glam types. Note that serialization should work between builds of glam with and without SIMD enabled

Feature gates

• scalar-math - compiles with SIMD support disabled.

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

When relevant, a left-handed co-ordinate system is used:

• +X - right
• +Y - up
• +Z - forward

The co-ordinate system primary affects functions that deal with Euler angle rotations.

Rotations follow the left-hand rule.

Design Philosophy

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

• Only single precision floating point (f32) arithmetic is supported
• No traits or generics for simplicity of implementation and usage
• All dependencies are optional (e.g. approx, rand and serde)
• Follows the [Rust API Guidelines] where possible
• Aiming for 100% test coverage
• Common functionality is benchmarked using [Criterion.rs]

Future work

• Writing documentation
• Experiment with replacing SSE2 code with f32x4 from the packed_simd library - this will mean other architectures get SIMD support
• Experiment with a using a 4x3 matrix as a 3D transform type that can be more efficient than Mat4 for certain operations like inverse and multiplies
• no-std support

Naming

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.

Support

If you are interested in contributing or have a request or suggestion [create an issue] on github.