Add a test: test_tetrahedra_collision_sensitivity.

[spline3.git] / src / Grid.hs

diff --git a/src/Grid.hs b/src/Grid.hs
index 3d636b53a780f465b515c6e45f8ee53b6e7f10ba..8ce2430d186870d7e7322d4bf5ff9e381870273c 100644 (file)
--- a/src/Grid.hs
+++ b/src/Grid.hs
@@ -8,10 +8,8 @@ import Test.QuickCheck (Arbitrary(..), Gen, Positive(..))
 
 import Cube (Cube(Cube), find_containing_tetrahedra)
 import FunctionValues
-import Misc (flatten)
 import Point (Point)
 import Tetrahedron (polynomial)
-import ThreeDimensional (contains_point)
 import Values (Values3D, dims, empty3d, zoom_shape)
 
 import qualified Data.Array.Repa as R
@@ -67,40 +65,72 @@ cube_at g i j k
     | i < 0 = Nothing
     | j < 0 = Nothing
     | k < 0 = Nothing
-    | i >= length (cubes g) = Nothing
-    | j >= length ((cubes g) !! i) = Nothing
-    | k >= length (((cubes g) !! i) !! j) = Nothing
-    | otherwise = Just $ (((cubes g) !! i) !! j) !! k
+    | k >= length (cubes g) = Nothing
+    | j >= length ((cubes g) !! k) = Nothing
+    | i >= length (((cubes g) !! k) !! j) = Nothing
+    | otherwise = Just $ (((cubes g) !! k) !! j) !! i
+
+
+
+--   The first cube along any axis covers (-h/2, h/2). The second
+--   covers (h/2, 3h/2).  The third, (3h/2, 5h/2), and so on.
+--
+--   We translate the (x,y,z) coordinates forward by 'h/2' so that the
+--   first covers (0, h), the second covers (h, 2h), etc. This makes
+--   it easy to figure out which cube contains the given point.
+calculate_containing_cube_coordinate :: Grid -> Double -> Int
+calculate_containing_cube_coordinate g coord
+    -- Don't use a cube on the boundary if we can help it. This
+    -- returns cube #1 if we would have returned cube #0 and cube #1
+    -- exists.
+    | coord == offset && (xsize > 0 && ysize > 0 && zsize > 0) = 1
+    | otherwise = (ceiling ( (coord + offset) / cube_width )) - 1
+    where
+      (xsize, ysize, zsize) = dims (function_values g)
+      cube_width = (h g)
+      offset = cube_width / 2
+
+
+-- | Takes a 'Grid', and returns a 'Cube' containing the given 'Point'.
+--   Since our grid is rectangular, we can figure this out without having
+--   to check every cube.
+find_containing_cube :: Grid -> Point -> Cube
+find_containing_cube g p =
+    case cube_at g i j k of
+      Just c -> c
+      Nothing -> error "No cube contains the given point."
+    where
+      (x, y, z) = p
+      i = calculate_containing_cube_coordinate g x
+      j = calculate_containing_cube_coordinate g y
+      k = calculate_containing_cube_coordinate g z
 
 
--- | Takes a 'Grid', and returns all 'Cube's belonging to it that
---   contain the given 'Point'.
-find_containing_cubes :: Grid -> Point -> [Cube]
-find_containing_cubes g p =
-    filter contains_our_point all_cubes
-    where
-      all_cubes = flatten $ cubes g
-      contains_our_point = flip contains_point p
+{-# INLINE zoom_lookup #-}
+zoom_lookup :: Grid -> a -> (R.DIM3 -> Double)
+zoom_lookup g _ = zoom_result g
+
+
+{-# INLINE zoom_result #-}
+zoom_result :: Grid -> R.DIM3 -> Double
+zoom_result g (R.Z R.:. i R.:. j R.:. k) =
+  f p
+  where
+    i' = fromIntegral i
+    j' = fromIntegral j
+    k' = fromIntegral k
+    p  = (i', j', k') :: Point
+    c = find_containing_cube g p
+    t = head (find_containing_tetrahedra c p)
+    f = polynomial t
 
 
 zoom :: Grid -> Int -> Values3D
 zoom g scale_factor
     | xsize == 0 || ysize == 0 || zsize == 0 = empty3d
     | otherwise =
-        R.traverse arr transExtent (\_ -> newlookup)
+        R.force $ R.traverse arr transExtent (zoom_lookup g)
           where
-            fvs = function_values g
-            (xsize, ysize, zsize) = dims fvs
-            arr = fvs
+            arr = function_values g
+            (xsize, ysize, zsize) = dims arr
             transExtent = zoom_shape scale_factor
-            newlookup :: R.DIM3 -> Double
-            newlookup (R.Z R.:. i R.:. j R.:. k) =
-                f p
-                  where
-                    i' = fromIntegral i
-                    j' = fromIntegral j
-                    k' = fromIntegral k
-                    p = (i', j', k') :: Point
-                    c = head (find_containing_cubes g p)
-                    t = head (find_containing_tetrahedra c p)
-                    f = polynomial t