https://github.com/micycle1/balaban-intersection

Implements the Balaban algorithm for finding intersecting segment pairs from a set of line segments.
https://github.com/micycle1/balaban-intersection

algorithm geometry-algorithms intersection segment segment-intersection

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Implements the Balaban algorithm for finding intersecting segment pairs from a set of line segments.

• Host: GitHub
• URL: https://github.com/micycle1/balaban-intersection
• Owner: micycle1
• Created: 2021-04-14T20:39:12.000Z (almost 4 years ago)
• Default Branch: main
• Last Pushed: 2021-06-18T08:36:21.000Z (over 3 years ago)
• Last Synced: 2024-11-17T08:37:53.994Z (2 months ago)
• Topics: algorithm, geometry-algorithms, intersection, segment, segment-intersection
• Language: Java
• Homepage:
• Size: 2.89 MB
• Stars: 3
• Watchers: 3
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: README.md

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README

        
[![](https://jitpack.io/v/micycle1/balaban-intersection.svg)](https://jitpack.io/#micycle1/balaban-intersection)

# Balaban Line Segments Intersection



  

  



## Overview

Reporting of segment set intersections is one of the

fundamental problems of computational geometry. This library implements *Ivan J. Balaban*'s [*Intermediate Algorithm*](https://www2.cs.sfu.ca/~binay/813.2011/Balaban.pdf) for finding intersecting segment pairs from a given set of N segments in the plane.

This algorithm has complexity *O( n\*log2(n) + k )* (where k is the number of intersecting pairs), which is **much** faster than the more commonly implemented *O( (n+k)\*log(n) )* *Bentley–Ottmann* algorithm for the same problem. In practice therefore, this library processes sizeable segment sets orders of magnitude more quickly than existing (Java) *Bentley–Ottmann* implementations.

This repository improves the abandoned original project from *Google Code Archive* whose author was [Taras](https://github.com/taarraas), and is provided as an artifact via [Jitpack](https://jitpack.io/#micycle1/balaban-intersection) for easy use in Maven/Gradle projects.

## Input

The algorithm processes a single collection of line segments.

The algorithm itself does not check for or handle *degenerate* inputs and will error (generally a stack overflow) on such inputs. The library offers the `findDegenerateSegments()` method to identify degenerate segments before processing.

Segment sets are degenerate when:

- Contains a vertical segment (whose vertices have the same X coordinate)

- Contains segments where a vertex from each share an x coordinate.

## Usage

The algorithm does not natively compute **points** of intersection. Rather, it returns intersecting **segment pairs**.

You must provide a callback function to the solver: *it* provides intersecting pairs — *you* decide what to do with them.

### Code Example

```

Random r = new Random(0);

Collection segments = new ArrayList<>();

for (int i = 0; i < 2000; i++) {

	segments.add(new Segment(r.nextDouble(), r.nextDouble(), r.nextDouble(), r.nextDouble()));

}

Collection points = new ArrayList<>();

BalabanSolver balabanSolver = new BalabanSolver((a, b) -> {

    	// will be called by the solver for each intersecting pair

	points.add(a.getIntersection(b));

});

balabanSolver.computeIntersections(segments);

```