3a7923ea92
# Objective Augment Bevy's random sampling capabilities by providing good tools for producing random directions and rotations. ## Solution The `rand` crate has a natural tool for providing `Distribution`s whose output is a type that doesn't require any additional data to sample values — namely, [`Standard`](https://docs.rs/rand/latest/rand/distributions/struct.Standard.html). Here, our existing `ShapeSample` implementations have been put to good use in providing these, resulting in patterns like the following: ```rust // Using thread-local rng let random_direction1: Dir3 = random(); // Using an explicit rng let random_direction2: Dir3 = rng.gen(); // Using an explicit rng coupled explicitly with Standard let random_directions: Vec<Dir3> = rng.sample_iter(Standard).take(5).collect(); ``` Furthermore, we have introduced a trait `FromRng` which provides sugar for `rng.gen()` that is more namespace-friendly (in this author's opinion): ```rust let random_direction = Dir3::from_rng(rng); ``` The types this has been implemented for are `Dir2`, `Dir3`, `Dir3A`, and `Quat`. Notably, `Quat` uses `glam`'s implementation rather than an in-house one, and as a result, `bevy_math`'s "rand" feature now enables that of `glam`. --- ## Changelog - Created `standard` submodule in `sampling` to hold implementations and other items related to the `Standard` distribution. - "rand" feature of `bevy_math` now enables that of `glam`. --- ## Discussion From a quick glance at `Quat`'s distribution implementation in `glam`, I am a bit suspicious, since it is simple and doesn't match any algorithm that I came across in my research. I will do a little more digging as a follow-up to this and see if it's actually uniform (maybe even using those tools I wrote — what a thrill). As an aside, I'd also like to say that I think [`Distribution`](https://docs.rs/rand/latest/rand/distributions/trait.Distribution.html) is really, really good. It integrates with distributions provided externally (e.g. in `rand` itself and its extensions) along with doing a good job of isolating the source of randomness, so that output can be reliably reproduced if need be. Finally, `Distribution::sample_iter` is quite good for ergonomically acquiring lots of random values. At one point I found myself writing traits to describe random sampling and essentially reinvented this one. I just think it's good, and I think it's worth centralizing around to a significant extent.
60 lines
1.7 KiB
Rust
60 lines
1.7 KiB
Rust
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
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#![forbid(unsafe_code)]
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#![doc(
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html_logo_url = "https://bevyengine.org/assets/icon.png",
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html_favicon_url = "https://bevyengine.org/assets/icon.png"
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)]
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//! Provides math types and functionality for the Bevy game engine.
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//!
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//! The commonly used types are vectors like [`Vec2`] and [`Vec3`],
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//! matrices like [`Mat2`], [`Mat3`] and [`Mat4`] and orientation representations
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//! like [`Quat`].
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mod affine3;
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mod aspect_ratio;
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pub mod bounding;
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mod common_traits;
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pub mod cubic_splines;
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mod direction;
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mod float_ord;
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pub mod primitives;
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mod ray;
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mod rects;
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mod rotation2d;
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#[cfg(feature = "rand")]
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pub mod sampling;
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pub use affine3::*;
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pub use aspect_ratio::AspectRatio;
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pub use common_traits::*;
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pub use direction::*;
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pub use float_ord::*;
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pub use ray::{Ray2d, Ray3d};
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pub use rects::*;
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pub use rotation2d::Rotation2d;
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#[cfg(feature = "rand")]
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pub use sampling::{FromRng, ShapeSample};
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/// The `bevy_math` prelude.
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pub mod prelude {
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#[doc(hidden)]
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#[cfg(feature = "rand")]
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pub use crate::sampling::{FromRng, ShapeSample};
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#[doc(hidden)]
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pub use crate::{
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cubic_splines::{
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CubicBSpline, CubicBezier, CubicCardinalSpline, CubicCurve, CubicGenerator,
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CubicHermite, CubicNurbs, CubicNurbsError, CubicSegment, RationalCurve,
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RationalGenerator, RationalSegment,
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},
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direction::{Dir2, Dir3, Dir3A},
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primitives::*,
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BVec2, BVec3, BVec4, EulerRot, FloatExt, IRect, IVec2, IVec3, IVec4, Mat2, Mat3, Mat4,
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Quat, Ray2d, Ray3d, Rect, Rotation2d, URect, UVec2, UVec3, UVec4, Vec2, Vec2Swizzles, Vec3,
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Vec3Swizzles, Vec4, Vec4Swizzles,
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};
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}
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pub use glam::*;
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