Data.Geo.Jord.Polygon

Types and functions for working with polygons at the surface of a spherical celestial body.

In order to use this module you should start with the following imports:

import qualified Data.Geo.Jord.Geodetic as Geodetic
import qualified Data.Geo.Jord.Polygon as Polygon

The Polygon type

data Polygon a

A polygon whose vertices are horizontal geodetic positions.

Instances

Model a => Eq (Polygon a)

Defined in Data.Geo.Jord.Polygon

Methods

(==) :: Polygon a -> Polygon a -> Bool

(/=) :: Polygon a -> Polygon a -> Bool

Spherical a => Show (Polygon a)

Defined in Data.Geo.Jord.Polygon

Methods

showsPrec :: Int -> Polygon a -> ShowS

show :: Polygon a -> String

showList :: [Polygon a] -> ShowS

vertices :: Polygon a -> [HorizontalPosition a]

vertices of the polygon in clockwise order.

edges :: Polygon a -> [MinorArc a]

edges of the polyon in clockwise order.

concave :: Polygon a -> Bool

whether the polygon is concave.

smart constructors

data Error

Error returned when attempting to create a polygon from invalid data.

Constructors

NotEnoughVertices

less than 3 vertices were supplied.

InvalidEdge

2 consecutives vertices are antipodal or equal.

InvalidRadius

radius of circle or arc is <= 0.

EmptyArcRange

arc start angle == end angle.

SeflIntersectingEdge

2 edges of the polygon intersect.

Instances

Eq Error

Defined in Data.Geo.Jord.Polygon

Methods

(==) :: Error -> Error -> Bool

(/=) :: Error -> Error -> Bool

Show Error

Defined in Data.Geo.Jord.Polygon

Methods

showsPrec :: Int -> Error -> ShowS

show :: Error -> String

showList :: [Error] -> ShowS

simple :: Spherical a => [HorizontalPosition a] -> Either Error (Polygon a)

Simple polygon (outer ring only and not self-intersecting) from given vertices. Returns an error (Left) if:

• less than 3 vertices are given.
• the given vertices defines self-intersecting edges.
• the given vertices contains duplicated positions or antipodal positions.

circle :: Spherical a => HorizontalPosition a -> Length -> Int -> Either Error (Polygon a)

Circle from given centre and radius. The resulting polygon contains nb vertices equally distant from one another. Returns an error (Left) if:

• given radius is 0
• given number of positions is less than 3

arc :: Spherical a => HorizontalPosition a -> Length -> Angle -> Angle -> Int -> Either Error (Polygon a)

Arc from given centre, radius and given start/end angles. The resulting polygon contains nb vertices equally distant from one another. Returns an error (Left) if:

• given radius is 0
• given number of positions is less than 3
• difference between start and end angle is 0

calculations

contains :: Spherical a => Polygon a -> HorizontalPosition a -> Bool

contains poly p returns True if position p is enclosed by the vertices of polygon poly - see enclosedBy.

triangulate :: Spherical a => Polygon a -> [Triangle a]

Triangulates the given polygon using the ear clipping method.

May return an empty list if the algorithm fails to find an ear (which probably indicates a bug in the implementation).