bevy_math

Vector and matrix math, geometric primitives, sampled curves, easing functions, and the deterministic-math wrappers (ops) that the rest of the workspace uses instead of f32::sin and friends.

Purpose

bevy_math is the math substrate of Bevy. It exists for a few reasons:

1. Re-export glam types (Vec2, Vec3, Quat, Mat4, …) under stable paths so other crates don't pin a glam version.
2. Provide a curve framework (Curve trait, easing, sampling).
3. Provide geometric primitives (Circle, Sphere, Triangle3d, Capsule3d, Polygon) and operations on them (intersections, sampling, area/volume).
4. Provide deterministic math wrappers in ops:: that route through libm when the libm feature is on.

Directory layout

crates/bevy_math/src/
├── lib.rs            # Re-exports glam, exposes ops/curve/primitives modules
├── ops.rs            # Deterministic float ops (powf, sin, cos, …)
├── primitives/       # Geometric primitive types
├── curve/            # Curve trait, easing functions, samplers
├── bounding/         # AABB, sphere, plane, ray
├── compass.rs        # CompassQuadrant, CompassOctant
├── direction.rs      # Dir2, Dir3 (unit-vector wrappers)
├── ray.rs, rects.rs
├── isometry.rs       # Isometry2d, Isometry3d
├── sampling/         # Random sampling on shapes
├── cubic_splines/    # Bezier, B-spline, cubic Hermite
└── …

Key abstractions

Type	File	Description
Vec2 / Vec3 / Quat / Mat4	re-exported from glam in lib.rs	Bread-and-butter math types.
Dir2 / Dir3	crates/bevy_math/src/direction.rs	Compile-time unit-vector wrapper.
Curve trait	crates/bevy_math/src/curve/mod.rs	t -> sample with metadata.
EaseFunction	crates/bevy_math/src/curve/easing.rs	Built-in easings (sine, quad, cubic, elastic, bounce, …).
Aabb2d / Aabb3d / BoundingCircle / BoundingSphere	bounding/	Bounding volumes with intersection tests.
Ray2d / Ray3d	crates/bevy_math/src/ray.rs	Origin + direction.
Primitive shapes	crates/bevy_math/src/primitives/	Circle, Annulus, Triangle2d, Rectangle, Polygon, Sphere, Cuboid, Cylinder, Capsule3d, Cone, Torus, etc.
ops::	crates/bevy_math/src/ops.rs	sin, cos, powf, ln, etc — deterministic via libm.

How it works

Determinism

clippy.toml bans direct calls to f32::sin, f32::powf, etc across the workspace. bevy_math::ops::* is the workspace-wide replacement: with the libm feature on, these route through libm for cross-platform reproducibility (important for replays and rollback netcode); with libm off, they fall back to the standard library. The ops module is no_std-friendly.

Curves

A Curve produces a value at a parameter t. The trait has methods to map, blend, sample at uniform intervals, and integrate. EaseFunction provides the standard ~30 easing curves; combinators in curve/ let you splice or repeat curves.

The animation system in bevy_animation uses curves to animate any reflectable field.

Primitives

Each primitive shape implements Primitive2d / Primitive3d, which exposes area, perimeter/volume, and (in many cases) point-in-shape tests. They are also Meshable, meaning bevy_mesh can produce a Mesh from them.

use bevy::prelude::*;
let cube_mesh = Cuboid::new(1.0, 1.0, 1.0).mesh();
let sphere_mesh = Sphere::new(0.5).mesh().ico(4).unwrap();

Bounding volumes

The bounding/ module provides AABB / bounding circle / bounding sphere with IntersectsVolume / BoundingVolume traits. Used by frustum culling, ray casting, picking, and many gameplay queries.

Integration points

• Depends on: glam, serde (optional), libm (optional), rand (optional, for sampling).
• Depended on by: Practically every other crate. Math types are pervasive.

Entry points for modification

• New primitive: add a struct under primitives/, implement Primitive2d/Primitive3d, and (if it should generate a mesh) implement Meshable in bevy_mesh.
• New easing function: add a variant to EaseFunction in curve/easing.rs. The graphs documented in rustdoc are generated by tools/build-easefunction-graphs.
• New curve combinator: curve/ is full of templates.
• Adding a deterministic op: ops.rs and add a disallowed-methods entry in clippy.toml.

See also

• bevy_animation — primary consumer of Curve.
• bevy_mesh — uses Primitive*d::mesh().
• bevy_color — sister crate for color spaces.