X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FFace.hs;h=f4bc1580882e6c8ba9050462948d794dc65a13d2;hb=539486a032dbd760bf01c37d6d8e063aaf4a59bc;hp=3f1c223e10b3d28516c1c052fe4532f96633adf0;hpb=3cba7ca0c0b39cfd132a3b6ee255c377041cefb5;p=spline3.git

diff --git a/src/Face.hs b/src/Face.hs
index 3f1c223..f4bc158 100644
--- a/src/Face.hs
+++ b/src/Face.hs
@@ -1,23 +1,31 @@
-module Face
+-- | The Face module just contains the definition of the 'Face' data
+--   type and its two typeclass instances.
+--
+module Face (
+  Face(..),
+  center )
 where
 
-import Point
-import ThreeDimensional
+import Point ( Point(..), scale )
 
-data Face = Face { v0 :: Point,
-                   v1 :: Point,
-                   v2 :: Point,
-                   v3 :: Point }
+data Face = Face { v0 :: !Point,
+                   v1 :: !Point,
+                   v2 :: !Point,
+                   v3 :: !Point }
           deriving (Eq)
 
 instance Show Face where
-    show f = "Face:\n" ++
-             "  v0: " ++ (show (v0 f)) ++ "\n" ++
-             "  v1: " ++ (show (v1 f)) ++ "\n" ++
-             "  v2: " ++ (show (v2 f)) ++ "\n" ++
-             "  v3: " ++ (show (v3 f)) ++ "\n"
+    show (Face v0' v1' v2' v3') =
+      "Face:\n" ++
+        "  v0: " ++ (show v0') ++ "\n" ++
+        "  v1: " ++ (show v1') ++ "\n" ++
+        "  v2: " ++ (show v2') ++ "\n" ++
+        "  v3: " ++ (show v3') ++ "\n"
 
-instance ThreeDimensional Face where
-    center f = ((v0 f) + (v1 f) + (v2 f) + (v3 f)) `scale` (1/4)
-    -- Too lazy to implement this right now.
-    contains_point _ _ = False
+-- | Returns the center of the given face. Since a face is just
+--   square, we can average the four vertices to find its center. This
+--   is useful because the center of a face is always a vertex of a
+--   tetrahedron.
+center :: Face -> Point
+center (Face v0' v1' v2' v3') =
+  (v0' + v1' + v2' + v3') `scale` (1/4)