https://github.com/pkinney/segseg_ex

Segment-segment intersection classifier and calculator for Elixir
https://github.com/pkinney/segseg_ex

Last synced: 8 days ago
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Segment-segment intersection classifier and calculator for Elixir

• Host: GitHub
• URL: https://github.com/pkinney/segseg_ex
• Owner: pkinney
• License: mit
• Created: 2016-04-01T14:46:12.000Z (over 8 years ago)
• Default Branch: master
• Last Pushed: 2023-05-30T17:11:08.000Z (over 1 year ago)
• Last Synced: 2024-09-01T02:38:30.383Z (2 months ago)
• Language: Elixir
• Homepage:
• Size: 159 KB
• Stars: 6
• Watchers: 1
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

        
# Segment-Segment Intersection

![Build Status](https://github.com/pkinney/segseg_ex/actions/workflows/ci.yaml/badge.svg)

[![Hex.pm](https://img.shields.io/hexpm/v/seg_seg.svg)](https://hex.pm/packages/seg_seg)

[![Documentation](https://img.shields.io/badge/documentation-gray)](https://hexdocs.pm/seg_seg)

Calculates intersection type and location for two line segments.

![Classification of segment-segment intersection](http://i.imgbox.com/hO3zHfNR.png)

## Installation

```elixir

defp deps do

  [{:seg_seg, "~> 1.0"}]

end

```

## Usage

**[Full Documentation](https://hexdocs.pm/seg_seg/SegSeg.html)**

The `SegSeg` module provides a function `intersection` that calculates the

intersection between two line segments and returns a tuple with three elements:

1. Boolean `true` if the two segments intersect at all, `false` if they are

   disjoint

2. An atom representing the classification of the intersection:

- `:interior` - the segments intersect at a point that is interior to both

- `:vertex` - the segments intersect at an endpoint of one or both segments

- `:edge` - the segments are parallel, collinear, and overlap for some non-zero

  length

- `:disjoint` - no intersection exists between the two segments

3. A tuple `{x, y}` representing the point of intersection if the intersection

   is classified as `:interior` or `:vertex`, otherwise `nil`.

## Examples

```elixir

SegSeg.intersection({2, -3}, {4, -1}, {2, -1}, {4, -3}) #=> {true, :interior, {3.0, -2.0}}

SegSeg.intersection({-1, 3}, {2, 4}, {-1, 4}, {-1, 5}) #=> {false, :disjoint, nil}

SegSeg.intersection({1, 2}, {3, 0}, {2, 1}, {4, 2}) #=> {true, :vertex, {2, 1}}

SegSeg.intersection({-1, 0}, {0, 2}, {1, 4}, {-1, 0}) #=> {true, :edge, nil}

```

## Float Precision Issues

It is possible that floating point math imprecision can cause incorrect results for certain inputs.  In situations where this may cause issues, an `epsilon` options is available.  When set to `true` intersection comparisons are made with a very small `epsilon` based on the minimum of the lengths of the provided segment times a very small number (currently 0.0000000001). `epsilon` can also be set to a specific number that will be used as the epsilon value. This eliminates most rounding error, but of course could cause false results in certain situations. This currently only effects `:vertex` results but might be expanded to `:edge` in the future.

```elixir

SegSeg.intersection({4, 3}, {4, 7}, {6.05, 9.05}, {3.95, 6.95}) #=> {true, :interior, {4.0, 6.999999999999998}}

SegSeg.intersection({4, 3}, {4, 7}, {6.05, 9.05}, {3.95, 6.95}, epsilon: true) #=> {true, :vertex, {4, 7}}

```

## Tests

```bash

> mix test

```