# Polygonical

A library for interacting with polygons on a 2d plane.

## Examples

Rotate a polygon:
```rust
    use polygonical::polygon::Polygon;
    use polygonical::point::Point;

    let poly = Polygon::new(vec![
        Point::new(0.0, 1.0),
        Point::new(1.0, 1.0),
        Point::new(1.0, 0.0),
    ]);

    // get the area of the polygon
    let area = poly.area();

    // rotate the polygon around its own center by 90 degrees
    let rotated = poly.rotate_around_center(90.0_f64.to_radians());

    println!("area: {} rotated: {}", area, rotated);
```


Create an approximation of a circle:

```rust
    use polygonical::polygon::Polygon;
    use polygonical::point::Point;

    let num_points = 16;
    let radius = 2.0;
    let center = Point::new(10.0, 20.0);

    // Note: we use an integer number of degrees here because rust won't let you iterate over floats like this.
    let points = (0..360).step_by(360/num_points)
        .map(|a| Point::new(radius, 0.0).rotate((a as f64).to_radians()).translate(&center))
        .collect();

    let circle = Polygon::new(points);
     
    let approx_area = circle.area();
    let area = std::f64::consts::PI * radius * radius;

    println!("area: {} aprox_area: {} difference: {}", area, approx_area, area - approx_area);
```

## Features

* Points
* Polygons
* Bounding boxes
* Translations of points
* Polygons contain points
* Polygon is_self_intersecting
* Polygon area
* Translations of polygons
* Rotations of points
* Rotations of polygons
* Overlap detection
* Contains detection
* Polygon unions

## Wanted Features

Things we want to implement but haven't yet.

* Scale of points
* Scale of polygons
* Polygon subtraction

## Unwanted Features

Things this library won't do.

* 3d Geometry
* Output to things like svg (that is for another library)
* Coordinate system transforms, epsg codes, pixel space to world space etc.

## Design goals

* Correct
* Safe
* Fast

In that order

## Limitations / Warnings

Polygons must be specified with the points going clockwise around them. Several algorithms only work when points are defined
clockwise. There is no detection of this, it will probably cause weird results, it has not been tested.