gemath

gemath is a math crate for game/engine code that cares about making invalid math hard to write.

Instead of “just vectors and matrices”, gemath leans into type-level correctness:

• Type-level units (e.g. Meters, Pixels) and type-level coordinate spaces (e.g. World, Local, Screen) are carried by core types: Vec*<Unit, Space>, Mat*<Unit, Space>, Quat<Unit, Space>, and friends.
• Typed angles (Radians / Degrees) are the default posture: rotation APIs take angle types, not “mystery f32”.
• Fallible operations are explicit: “can this fail?” shows up in the type (Option) and in naming (try_*, checked_*), with a crate-wide policy.

If you like glam’s ergonomics but want the compiler to help you keep your spaces/units/angles straight, gemath is built for that.

The killer feature: Unit + Space tags that don’t get in your way

Use ()/() when you don’t care — or opt into safety by tagging your math:

use gemath::{Meters, Pixels, Screen, Vec2, World};

let p_world: Vec2<Meters, World> = Vec2::new(10.0, 20.0);
let p_screen: Vec2<Pixels, Screen> = Vec2::new(640.0, 360.0);

// let _oops = p_world + p_screen;
// ^ does not compile: different Unit and Space tags

Typed angles (Degrees/Radians) by default

use gemath::{Degrees, Vec2};

let v: Vec2<(), ()> = Vec2::new(1.0, 0.0);
let v90 = v.rotate_deg(Degrees(90.0));
assert!((v90 - Vec2::new(0.0, 1.0)).length() < 1e-5);

Geometry + collision helpers with structured “hit” results

use gemath::{ray2_circle_cast, Circle, Ray2, Vec2};

let circle: Circle<(), ()> = Circle::new(Vec2::new(0.0, 0.0), 1.0);
let ray: Ray2<(), ()> = Ray2::new(Vec2::new(-2.0, 0.0), Vec2::new(1.0, 0.0));

let hit = ray2_circle_cast(ray, circle).unwrap();
assert!((hit.t - 1.0).abs() < 1e-6);
assert!((hit.point - Vec2::new(-1.0, 0.0)).length() < 1e-6);
assert!((hit.normal - Vec2::new(-1.0, 0.0)).length() < 1e-6);

Docs for contributors (start here)

The developer docs live in docs/:

• Docs index: docs/README.md
• Feature flags / minimal builds: docs/FEATURES.md
• Build + test matrix: docs/DEVELOPMENT.md
• Copy/paste cookbook: docs/COOKBOOK.md
• API conventions: docs/API_CONVENTIONS.md
• Design notes (fallible ops, scalar policy, spatial prototypes): docs/

no_std posture (real, tested)

gemath is designed so you can keep the “core math” tiny:

# minimal no_std build (no allocation)
cargo build --no-default-features --features libm

For the full supported/tested matrix (including alloc, geometry, collision, spatial, serde, mint), see docs/DEVELOPMENT.md.

Acknowledgments

gemath was inspired by the work of @gingerBill's gb_math.h Vector math library and adapts many of Bill's original ideas.