glam

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

Development status

glam is in a pre-alpha stage. Base functionality has been implemented and the look and feel of the API has solidified.

Only single precision floating point arithmetic (i.e. f32) is currently supported.

At this point I'm looking to see if people are interested in using it and how they find it. So it is possible that future versions may include API changes or even changes in the conventions listed below.

Features

• vectors: Vec3, Vec3, Vec4
• square matrices: Mat2, Mat3, Mat4
• a quaternion type: Quat
• an angle type: Angle

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.

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

Default features

• approx - implementations of the AbsDiffEq and UlpsEq traits for all glam types
• 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

Feature gates

• no-simd - compiles with SIMD support disabled

Conventions

Row vectors

glam interprets vectors as row matrices (also known as "row vectors") meaning when transforming a vector with a matrix the matrix goes on the right, e.g. v' = vM. DirectX uses row vectors, OpenGL uses column vectors. There are pros and cons to both, the main advantage of row vectors is multiplication reads from left to right.

For example:

result = input * local_to_object * object_to_world

Input is in local space, it get transformed into object space before the final transform into world space.

Row-major order

Matrices are stored in row major format.

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 f32 arithmetic is supported for now (no f64)
• No traits or generics
• Dependencies are optional (e.g. mint, rand and serde)
• Follows a Rust style, e.g. methods instead of free functions
• Aiming for 100% test coverage for both SIMD and scalar code paths
• Common functionality is benchmarked

Future work

• 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.