src/Face.hs

   1 -- | The Face module just contains the definition of the 'Face' data
   2 --   type and its two typeclass instances.
   3 module Face
   4   ( Face(..) )
   5 where
   6
   7 import Point
   8 import ThreeDimensional
   9
  10 data Face = Face { v0 :: Point,
  11                    v1 :: Point,
  12                    v2 :: Point,
  13                    v3 :: Point }
  14           deriving (Eq)
  15
  16 instance Show Face where
  17     show f = "Face:\n" ++
  18              "  v0: " ++ (show (v0 f)) ++ "\n" ++
  19              "  v1: " ++ (show (v1 f)) ++ "\n" ++
  20              "  v2: " ++ (show (v2 f)) ++ "\n" ++
  21              "  v3: " ++ (show (v3 f)) ++ "\n"
  22
  23 -- | The 'Face' type is an instance of 'ThreeDimensional' so that we
  24 --   can call the 'center' function on it. This is useful because the
  25 --   center of a face is always a vertex of a tetrahedron.
  26 instance ThreeDimensional Face where
  27     -- | Since a face is square, we can just average the four vertices
  28     --   to find the center.
  29     center f = ((v0 f) + (v1 f) + (v2 f) + (v3 f)) `scale` (1/4)
  30
  31     -- | It's possible to implement this, but it hasn't been done
  32     --   yet. A face will contain a point if the point lies in the same
  33     --   plane as the vertices of the face, and if it falls on the
  34     --   correct side of the four sides of the face.
  35     contains_point _ _ = False