iOverlay

The iOverlay library provides high-performance boolean operations on polygons, including union, intersection, difference, and xor. It is designed for applications that require precise polygon operations, such as computer graphics, CAD systems, and geographical information systems (GIS). By supporting both integer (i32) and floating-point (f32, f64) APIs, iOverlay offers flexibility and precision across diverse use cases.

For detailed performance benchmarks, check out the Performance Comparison

Documentation

Try out iOverlay with an interactive demo:

• Stars Rotation
• Shapes Editor
• Overlay Editor

Features

• Boolean Operations: union, intersection, difference, and exclusion.
• String Line Operations: clip and slice.
• Polygons: with holes, self-intersections, and multiple contours.
• Simplification: removes degenerate vertices and merges collinear edges.
• Fill Rules: even-odd, non-zero, positive and negative.
• Data Types: Supports i32, f32, and f64 APIs.

Getting Started

Add the following to your Cargo.toml:

[dependencies]
i_overlay = "^1.9"

Simple Example

Here's an example of performing a union operation between two polygons:

// Define the subject "O"
let subj = [
    // main contour
    vec![
      [1.0, 0.0],
      [1.0, 5.0],
      [4.0, 5.0],
      [4.0, 0.0], // the contour is auto closed!
    ],
    // hole contour
    vec![
      [2.0, 1.0],
      [3.0, 1.0],
      [3.0, 4.0],
      [2.0, 4.0], // the contour is auto closed!
    ],
];

// Define the clip "-"
let clip = [
    // main contour
    [0.0, 2.0],
    [5.0, 2.0],
    [5.0, 3.0],
    [0.0, 3.0], // the contour is auto closed!
];

let result = subj.overlay(&clip, OverlayRule::Union, FillRule::EvenOdd);

println!("result: {:?}", result);

The result is a vec of shapes:

[
    // first shape
    [
        // main contour (clockwise order)
        [
            [0.0, 2.0], [0.0, 3.0], [1.0, 3.0], [1.0, 5.0], [4.0, 5.0], [4.0, 3.0], [5.0, 3.0], [5.0, 2.0], [4.0, 2.0], [4.0, 0.0], [1.0, 0.0], [1.0, 2.0]
        ],
        // first hole (counterclockwise order)
        [
            [2.0, 2.0], [2.0, 1.0], [3.0, 1.0], [3.0, 2.0]
        ],
        // second hole (counterclockwise order)
        [
            [2.0, 4.0], [2.0, 3.0], [3.0, 3.0], [3.0, 4.0]
        ]
    ]
    // ... other shapes if present
]

The overlay function returns a Vec<Shapes>:

• Vec<Shape>: A collection of shapes.
• Shape: Represents a shape made up of:
  • Vec<Contour>: A list of contours.
  • The first contour is the outer boundary (clockwise), and subsequent contours represent holes (counterclockwise).
• Contour: A sequence of points (Vec<P: FloatPointCompatible>) forming a closed contour.

Note: Outer boundary contours have a clockwise order, and holes have a counterclockwise order. More information about contours.

Custom Point

iOverlay allows users to define custom point types, as long as they implement the FloatPointCompatible trait.

#[derive(Clone, Copy, Debug)]
struct CustomPoint {
  x: f32,
  y: f32,
}

impl FloatPointCompatible<f32> for CustomPoint {
  fn from_xy(x: f32, y: f32) -> Self {
    Self { x, y }
  }

  fn x(&self) -> f32 {
    self.x
  }

  fn y(&self) -> f32 {
    self.y
  }
}

let subj = [
    CustomPoint { x: 0.0, y: 0.0 },
    CustomPoint { x: 0.0, y: 3.0 },
    CustomPoint { x: 3.0, y: 3.0 },
    CustomPoint { x: 3.0, y: 0.0 },
];

let clip = [
    CustomPoint { x: 1.0, y: 1.0 },
    CustomPoint { x: 1.0, y: 2.0 },
    CustomPoint { x: 2.0, y: 2.0 },
    CustomPoint { x: 2.0, y: 1.0 },
];

let result = subj.overlay(&clip, OverlayRule::Difference, FillRule::EvenOdd);

println!("result: {:?}", result);

Slicing a Polygon by a String Line

let polygon = [
    [1.0, 1.0],
    [1.0, 4.0],
    [4.0, 4.0],
    [4.0, 1.0],
];

let slicing_line = [
    [3.0, 5.0],
    [2.0, 2.0],
    [3.0, 3.0],
    [2.0, 0.0],
];

let result = polygon.slice_by(&slicing_line, FillRule::NonZero);

println!("result: {:?}", result);

Clip a String Lines by a Polygon

let polygon = [
    [1.0, 1.0],
    [1.0, 4.0],
    [4.0, 4.0],
    [4.0, 1.0],
];

let string_line = [
    [3.0, 5.0],
    [2.0, 2.0],
    [3.0, 3.0],
    [2.0, 0.0],
];

let clip_rule = ClipRule { invert: false, boundary_included: false };
let result = string_line.clip_by(&polygon, FillRule::NonZero, clip_rule);

println!("result: {:?}", result);

Versioning Policy

This crate follows a pragmatic versioning approach:

PATCH updates (e.g., 1.8.1 → 1.8.2): Guaranteed to be backward-compatible, containing only bug fixes or small improvements.
MINOR updates (e.g., 1.8.0 → 1.9.0): Typically backward-compatible but may include changes to experimental or less commonly used APIs.
MAJOR updates (e.g., 1.x.x → 2.x.x): Reserved for significant breaking changes or major redesigns.

To minimize disruption, consider pinning dependencies when relying on specific versions.

Overlay Rules

Union, A or B

Intersection, A and B

Difference, A - B

Inverse Difference, B - A

Exclusion, A xor B