src/Face.hs

   1 -- | The Face module just contains the definition of the 'Face' data
   2 --   type and its two typeclass instances.
   3 --
   4 module Face (
   5   Face(..),
   6   center )
   7 where
   8
   9 import Point ( Point, scale )
  10
  11 data Face = Face { v0 :: !Point,
  12                    v1 :: !Point,
  13                    v2 :: !Point,
  14                    v3 :: !Point }
  15           deriving (Eq)
  16
  17 instance Show Face where
  18     show (Face v0' v1' v2' v3') =
  19       "Face:\n" ++
  20         "  v0: " ++ (show v0') ++ "\n" ++
  21         "  v1: " ++ (show v1') ++ "\n" ++
  22         "  v2: " ++ (show v2') ++ "\n" ++
  23         "  v3: " ++ (show v3') ++ "\n"
  24
  25 -- | Returns the center of the given face. Since a face is just
  26 --   square, we can average the four vertices to find its center. This
  27 --   is useful because the center of a face is always a vertex of a
  28 --   tetrahedron.
  29 center :: Face -> Point
  30 center (Face v0' v1' v2' v3') =
  31   (v0' + v1' + v2' + v3') `scale` (1/4)