Initial pass at shadows from level geometry

src/Geometry/Vector3D.hs

@@ -1,6 +1,7 @@
 {-# LANGUAGE BangPatterns #-}
 module Geometry.Vector3D
     where
+import Geometry.Vector
 import Geometry.Data
 
 infixl 6 +.+.+, -.-.-
@@ -40,3 +41,10 @@ crossProd (x,y,z) (a,b,c) =
     , z * a - x * c
     , x * b - y * a
     )
+
+rotate3 :: Float -> Point3 -> Point3
+{-# INLINE rotate3 #-}
+rotate3 a (x,y,z) = (x',y',z)
+  where 
+    (x',y') = rotateV a (x,y)
+