# glam
[![Build Status]][travis-ci] [![Coverage Status]][coveralls.io]
[![Latest Version]][crates.io] [![docs]][docs.rs]
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.
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
* 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`
### 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`][cgmath] and
[`nalgebra-glm`][nalgebra-glm] for common operations as tested by the [`mathbench`][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
### 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:
```
let result = input * local_to_object * object_to_world;
```
In the above example `input` is in local space, it is 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 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][coveralls.io]
* 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](LICENSE-APACHE)
or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](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.
[Build Status]: https://travis-ci.org/bitshifter/glam-rs.svg?branch=master
[travis-ci]: https://travis-ci.org/bitshifter/glam-rs
[Coverage Status]: https://coveralls.io/repos/github/bitshifter/glam-rs/badge.svg?branch=master
[coveralls.io]: https://coveralls.io/github/bitshifter/glam-rs?branch=master
[Code of Conduct]: https://www.rust-lang.org/en-US/conduct.html
[Latest Version]: https://img.shields.io/crates/v/glam.svg
[crates.io]: https://crates.io/crates/glam/
[docs]: https://docs.rs/glam/badge.svg
[docs.rs]: https://docs.rs/glam/
[Rust API Guidelines]: https://rust-lang-nursery.github.io/api-guidelines/
[Criterion.rs]: https://bheisler.github.io/criterion.rs/book/index.html
[cgmath]: https://github.com/rustgd/cgmath
[nalgebra-glm]: https://github.com/rustsim/nalgebra
[mathbench]: https://github.com/bitshifter/mathbench-rs
[create an issue]: https://github.com/bitshifter/glam-rs/issues