Module robust 

Robust geometric predicates for numerical stability.

This module provides numerically robust implementations of geometric predicates using Shewchuk’s adaptive precision floating-point arithmetic.

Core Predicates

The core predicates (orient2d, orient2d_filtered, point_in_triangle, is_convex, is_ccw, Orientation) are provided by u-geometry and re-exported here for API compatibility.

Nesting-Specific Utilities

• signed_area_robust: Signed polygon area with Kahan summation for numerical stability
• ScalingConfig: Coordinate scaling for integer-range robust arithmetic
• snap_to_grid / snap_polygon_to_grid: Grid-snapping utilities

References

• Shewchuk, J.R. (1997). “Adaptive Precision Floating-Point Arithmetic and Fast Robust Predicates for Computational Geometry”
• https://www.cs.cmu.edu/~quake/robust.html

Example

use u_nesting_core::robust::{orient2d, Orientation};

// Check orientation of three points
let a = (0.0, 0.0);
let b = (1.0, 0.0);
let c = (0.5, 1.0);

match orient2d(a, b, c) {
    Orientation::CounterClockwise => println!("Left turn"),
    Orientation::Clockwise => println!("Right turn"),
    Orientation::Collinear => println!("Straight"),
}

Structs

ScalingConfig

Configuration for coordinate scaling.

Enums

Orientation

Result of an orientation test.

Functions

is_ccw

Checks if a polygon has counter-clockwise winding order.

is_ccw_robust

Checks if a polygon has counter-clockwise winding order.

is_convex

Checks if a polygon is convex using robust orientation tests.

is_convex_robust

Checks if a polygon is convex using robust orientation tests.

orient2d

Determines the orientation of three points using exact arithmetic.

orient2d_filtered

Fast orientation test with exact fallback.

orient2d_raw

Returns the raw orientation determinant (twice the signed area).

point_in_triangle

Checks if a point lies strictly inside a triangle.

point_in_triangle_inclusive

Checks if a point lies inside or on the boundary of a triangle.

point_in_triangle_inclusive_robust

Checks if a point lies inside or on the boundary of a triangle.

point_in_triangle_robust

Checks if a point lies strictly inside a triangle.

signed_area_robust

Computes the signed area of a polygon using Kahan summation.

snap_polygon_to_grid

Snaps an entire polygon to a grid.

snap_to_grid

Snaps coordinates to a grid of the given resolution.