X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FFace.hs;h=f4bc1580882e6c8ba9050462948d794dc65a13d2;hb=0d037f5f0829d9ee7fcccc58570305623665f52e;hp=bc316a72cee9ae4eb815424b2ccbfe8705316911;hpb=6985f184b560c21139209e5cc9fd0eaf4a51715c;p=spline3.git

diff --git a/src/Face.hs b/src/Face.hs
index bc316a7..f4bc158 100644
--- a/src/Face.hs
+++ b/src/Face.hs
@@ -1,11 +1,12 @@
 -- | The Face module just contains the definition of the 'Face' data
 --   type and its two typeclass instances.
-module Face
-  ( Face(..) )
+--
+module Face (
+  Face(..),
+  center )
 where
 
-import Point
-import ThreeDimensional
+import Point ( Point(..), scale )
 
 data Face = Face { v0 :: !Point,
                    v1 :: !Point,
@@ -14,22 +15,17 @@ data Face = Face { v0 :: !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"
 
--- | The 'Face' type is an instance of 'ThreeDimensional' so that we
---   can call the 'center' function on it. This is useful because the
---   center of a face is always a vertex of a tetrahedron.
-instance ThreeDimensional Face where
-    -- | Since a face is square, we can just average the four vertices
-    --   to find the center.
-    center f = ((v0 f) + (v1 f) + (v2 f) + (v3 f)) `scale` (1/4)
-
-    -- | It's possible to implement this, but it hasn't been done
-    --   yet. A face will contain a point if the point lies in the same
-    --   plane as the vertices of the face, and if it falls on the
-    --   correct side of the four sides of the face.
-    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)