https://github.com/ahlusar1989/bentley-ottman

Bentley Ottman Algorithm to Validate Convex and Simple Polygons
https://github.com/ahlusar1989/bentley-ottman

Last synced: 23 days ago
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Bentley Ottman Algorithm to Validate Convex and Simple Polygons

• Host: GitHub
• URL: https://github.com/ahlusar1989/bentley-ottman
• Owner: ahlusar1989
• Created: 2017-01-28T19:31:25.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2023-01-10T03:32:30.000Z (almost 2 years ago)
• Last Synced: 2024-10-05T23:41:19.552Z (about 1 month ago)
• Language: JavaScript
• Homepage:
• Size: 30.3 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 6
• Metadata Files:
  • Readme: README.md

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README

        
Detecting polygon self-intersection in Javascript

============================================

An implementation of the O((n + k) log n) Bentley–Ottmann sweep-line algorithm for detecting crossings in a set of line segments (originally by Simon Tokumine's iteration of `sweepline`). The aim was to make something to rapidly detect self-intersecting polygons for client side validation before serialization and storage, but there's not much to stop it being used server-side (except it being more a statement of intent than actual production ready code).

* Note: This fork's refactoring does not contain any client side or browser examples - this entirely server side validation of floor plan data and geometries. This version also has all tests rewritten to validate floor-plan data for Property Service.

Development

===========

* node.js 6.9.1

* mocha

* chai

Notable Changes to Implementation

==============================================

1. ECMAScript classes that provide a much simpler and clearer syntax to create objects and deal with inheritance.

2. Point: refactor the `isLeftofSegment` of Class `Point` as a static method

3. Polygon: fix implicit global variables; rename the `simple_polygon` to `isSimplePolygon`; refactor the logic according to the rest of the classes

4. RedBlackTree: fix the implicit global variables in Kevin Lindsey's implementation;

5. Sweepline: Rename to Bentley-Ottman; improvements to SweepLine and SweepLine segment logic; refactor the logic according to the new constructor patterns

6. EventQueue: add the `next` method; refactor the logic according to the new constructor pattern

7. updates to the test spec for floor plan data

Reference Implementation

==============================================

http://geomalgorithms.com/a09-_avl_code.html#SweepLineClass

the above is the implementation of Bentley–Ottmann sweep-line algorithm with an AVL tree.

In use is a variant with the Red-Black tree in lieu of the AVL tree. It has some adjustments and methods (for example - no rotateLeft and rotateRight methods).

Tests

======

To run the tests, ensure you have node.js and npm, and necessary dev dependencies installed:

$ npm test

Note that this implementation currently doesn't validate polygons that share the same start and end vertex.

License

========

free