-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | Simple computation of visibility polygons.
--   
--   Simple computation of visibility polygons.
@package visibility
@version 0.1.0.2


-- | The algorithm is relatively simple. The points are sorted by their
--   polar angle relative to the reference point, keeping track of which
--   line segment they belong to. In this ordering, they are assigned tags
--   representing whether they are a start of a segment, or it's end. A
--   comparison is defined on those oriented segments that determines which
--   segment covers the other if viewed from the reference point. Then the
--   list of points is folded over by putting segments in a set, and
--   removing them from it when a starting point or an end point is
--   encountered, respectively. Every time the closest segment to the
--   reference point changes, we output two points of a visibility polygon
--   by computing relevant ray-segment intersections.
module Data.Geometry.Visibility
data Point
Point :: {-# UNPACK #-} !Double -> {-# UNPACK #-} !Double -> Point
data Polygon

-- | Construct a polygon from an simple polygon and a list of holes.
Polygon :: SimplePolygon -> [SimplePolygon] -> Polygon
newtype SimplePolygon

-- | Construct a simple polygon from points in a CCW order
Simple :: [Point] -> SimplePolygon

-- | Given a Point and a Polygon (possibly with holes), returns a
--   SimplePolygon describing the area visible from the Point inside of the
--   Polygon. O(n log n) where n is the number of points.
visibilityPolygon :: Point -> Polygon -> SimplePolygon