Crate clothoid 

clothoid

A Rust library for computing and fitting Clothoids (also known as Euler spirals or Cornu spirals). A clothoid is a curve whose curvature changes linearly with its arc length.

Usage

use clothoid::Clothoid;

let clothoid = Clothoid::new(1.0);
let angle = clothoid.direction_angle(0.5);

Choosing an Optimizer

The FitState supports two derivative-free optimizers for path fitting:

• Nelder-Mead (default) — The original simplex method. Fast per-iteration (500 evaluations per step), good for simple paths. Created with FitState::new(). Requires the nelder-mead feature (enabled by default).
• CMA-ES — Covariance Matrix Adaptation Evolution Strategy. More robust on difficult, non-convex landscapes but evaluates more candidates per generation. Created with FitState::cma_es(). Requires the cma-es feature (enabled by default).

Both share the same FitState API. Press O in the interactive demo to toggle between them.

Path Traits

When the path-traits feature is enabled (default), the crate provides ClothoidArc, LinearSegment, ClothoidPath, and Vec2 implementing the path_traits hierarchy. This allows downstream crates to treat clothoid paths generically via traits such as Path, SegmentedPath, Tangent, Heading, Curved, FrenetFrame, and Project.

use clothoid::ClothoidArc;
use clothoid::optimizer::Pose;
use path_traits::{Path, Heading, Curved};

let arc = ClothoidArc {
    start: Pose::new(0.0, 0.0, 0.0),
    ks: 0.0,
    ke: 1.0,
    length: 5.0,
    n_steps: 256,
};

let pt = arc.sample_at(2.5).unwrap();
let heading = arc.heading_at(2.5).unwrap();
let curvature = arc.curvature_at(2.5).unwrap();

Use Clothoid::into_arc to convert a Clothoid into a bounded arc:

use clothoid::Clothoid;
use path_traits::Path;

let c = Clothoid::new(2.0);
let arc = c.into_arc(4.0);
assert!((arc.length() - 4.0).abs() < 1e-10);

Features

• fresnel — enables high-precision Fresnel integral computation via the external fresnel crate. When disabled, uses an approximation based on auxiliary functions (Wilde 2009 / Abramowitz & Stegun).
• optimizers (default) — enables both nelder-mead and cma-es solvers, plus the fit module.
• nelder-mead — enables the Nelder-Mead simplex optimizer and the fit module.
• cma-es — enables the CMA-ES optimizer and the fit module.
• path-traits (default) — enables path_traits integration with ClothoidArc, LinearSegment, ClothoidPath, and Vec2.

Re-exports

pub use fit::DefaultPlanner;nelder-mead or cma-es

pub use fit::Planner;nelder-mead or cma-es

pub use optimizer::PlanObjective;

pub use optimizer::SymmetryMode;

pub use optimizer::CmaEs;cma-es

pub use optimizer::NelderMead;nelder-mead

pub use optimizer::Optimizer;nelder-mead or cma-es

pub use path_traits_impls::ArcSegment;path-traits

pub use path_traits_impls::ClothoidArc;path-traits

pub use path_traits_impls::ClothoidPath;path-traits

pub use path_traits_impls::LinearSegment;path-traits

pub use path_traits_impls::Vec2;path-traits

Modules

fitnelder-mead or cma-es

Incremental path fitting using clothoid segments.

optimizer

Path evaluation and optimization utilities for clothoid fitting.

path_traits_implspath-traits

Implementation of path_traits for clothoid types.

Structs

Clothoid

A Clothoid (Euler spiral) curve.

Point2

A point in 2D Cartesian space.