Crate max_inscribed_circle 

Maximum inscribed circle (MIC) solvers for polygons.

The maximum inscribed circle is the largest circle that fits entirely inside a polygon. Holes are respected: the circle has to clear interior rings as well as the exterior, so the solve runs against every boundary segment.

Quick start

use max_inscribed_circle::geo_types::{LineString, Polygon};
use max_inscribed_circle::{maximum_inscribed_circle, MicOptions};

let square = Polygon::new(
    LineString::from(vec![(0.0, 0.0), (4.0, 0.0), (4.0, 4.0), (0.0, 4.0), (0.0, 0.0)]),
    vec![],
);

let mic = maximum_inscribed_circle(&square, &MicOptions::default())?;
assert!((mic.center.x() - 2.0).abs() < 1e-9);
assert!((mic.radius - 2.0).abs() < 1e-9);

Solve pipeline

Two stages, both native Rust. MicResult::used_engine and MicResult::approach report which one produced the answer:

1. Closed-form fast paths for single-ring inputs of four or five vertices: triangle incenter, axis-aligned rectangle, then a convex-quad Chebyshev solve. Every result is re-measured against the segment table and falls through to the grid when the ring is not the class it claimed.
2. Grid search over the bounding box, a branch and bound driven by the 1-Lipschitz property of boundary distance, refining to a tolerance of diag * 1e-7, then a compass hill climb on the clearance field.

The radius a result reports is always the measured distance from its centre to the nearest boundary segment, so a returned circle fits the polygon. A degenerate input, such as a zero-area ring or a non-finite coordinate, fails fast with MicError::InvalidInput instead of returning a meaningless circle.

Entry points

Function	Use
maximum_inscribed_circle	one polygon
maximum_inscribed_circle_multipolygon	best circle across components
maximum_inscribed_circle_slice	rayon-parallel batch, input order preserved
maximum_inscribed_circle_with_workspace	reuse a MicWorkspace across calls

GEOS comparison

The bench-geos feature compiles mic::solver::bench_geos, which calls the GEOS MaximumInscribedCircle construct so benchmarks can cross-check the native solver. It is not an engine: nothing in mic calls it, and the default feature set does not compile it. GEOS runs the same cell-refinement branch and bound as the grid stage, so agreement between them means two implementations of one algorithm match, not that an independent method confirms the radius.

Features

Feature	Effect
bench-geos	comparison only: links the GEOS C library so benchmarks can compare solvers
geo-traits	generic solves over any geo_traits polygon, plus geo_types::Geometry dispatch
shewchuk	exact orient2d predicates from the robust crate in the containment and orientation tests
simd	4-lane batched segment distance via the stable wide crate
hotpath	#[hotpath::measure] instrumentation on the solver entry points
python	PyO3 extension module named max_inscribed_circle
extension-module	build the Python module as an importable extension

Default features are empty. The bench-geos feature links against the GEOS C library, and its build script expects GEOS_LIB_DIR and GEOS_VERSION when GEOS cannot be found through pkg-config.

C ABI

ffi exposes mic_solve, mic_solve_multipolygon and mic_options_default: flat coordinate arrays in, #[repr(C)] structs out, 0 on success and -1 on error, with panics caught at the boundary. The

Re-exports

pub use mic::workspace::MicWorkspace;

pub use mic::maximum_inscribed_circle;

pub use mic::maximum_inscribed_circle_multipolygon;

pub use mic::maximum_inscribed_circle_slice;

pub use mic::maximum_inscribed_circle_with_workspace;

pub use mic::MicApproach;

pub use mic::MicError;

pub use mic::MicOptions;

pub use mic::MicResult;

pub use mic::MicUsedEngine;

pub use geo_types;

Modules

ffi

C ABI for the MIC solvers (holes + multipolygon).

geo_interopgeo-traits

georust ecosystem interop (feature geo-traits).

mic

Maximum Inscribed Circle (MIC) solvers for polygonal inputs.

tuning

MIC tuning constants carried over from IGE ige-core::tuning.