Fix (I think) the cube offset issue.

[spline3.git] / src / Grid.hs

diff --git a/src/Grid.hs b/src/Grid.hs
index ab698c1ba537a96a7971fbd8b2505548bfde9c30..d87114fb2915903b8244fd9d86e3fa66b881905e 100644 (file)
--- a/src/Grid.hs
+++ b/src/Grid.hs
@@ -4,6 +4,7 @@
 module Grid
 where
 
+import Data.Array (Array, array, (!))
 import qualified Data.Array.Repa as R
 import Test.QuickCheck (Arbitrary(..), Gen, Positive(..))
 
@@ -15,6 +16,9 @@ import Tetrahedron (polynomial)
 import Values (Values3D, dims, empty3d, zoom_shape)
 
 
+type CubeGrid = Array (Int,Int,Int) Cube
+
+
 -- | Our problem is defined on a Grid. The grid size is given by the
 --   positive number h. The function values are the values of the
 --   function at the grid points, which are distance h from one
@@ -44,18 +48,27 @@ empty_grid :: Grid
 empty_grid = Grid 1 empty3d
 
 
--- | Returns a three-dimensional list of cubes centered on the grid
+-- | Returns a three-dimensional array of cubes centered on the grid
 --   points of g with the appropriate 'FunctionValues'.
-cubes :: Grid -> [[[Cube]]]
+cubes :: Grid -> CubeGrid
 cubes g
-    | xsize == 0 || ysize == 0 || zsize == 0 = [[[]]]
-    | otherwise =
-        [[[ Cube (h g) i j k (make_values fvs i j k) | i <- [0..xsize]]
-              | j <- [0..ysize]]
-              | k <- [0..zsize]]
-    where
-      fvs = function_values g
-      (xsize, ysize, zsize) = dims fvs
+  = array (lbounds, ubounds)
+           [ ((i,j,k), cube_ijk)
+                 | i <- [0..xmax],
+                   j <- [0..ymax],
+                   k <- [0..zmax],
+                   let delta = h g,
+                   let tet_vol = (1/24)*(delta^(3::Int)),
+                   let cube_ijk =
+                         Cube delta i j k (make_values fvs i j k) tet_vol]
+     where
+       xmax = xsize - 1
+       ymax = ysize - 1
+       zmax = zsize - 1
+       lbounds = (0, 0, 0)
+       ubounds = (xmax, ymax, zmax)
+       fvs = function_values g
+       (xsize, ysize, zsize) = dims fvs
 
 
 -- | Takes a grid and a position as an argument and returns the cube
@@ -63,24 +76,16 @@ cubes g
 --   position is outside of the grid), it will throw an error.
 cube_at :: Grid -> Int -> Int -> Int -> Cube
 cube_at g i j k
-    | i < 0 = error "i < 0 in cube_at"
-    | j < 0 = error "j < 0 in cube_at"
-    | k < 0 = error "k < 0 in cube_at"
-    | otherwise =
-        let zsize = length (cubes g) in
-          if k >= zsize then
-            error "k >= xsize in cube_at"
-          else
-            let ysize = length ((cubes g) !! k) in
-              if j >= ysize then
-                error "j >= ysize in cube_at"
-              else
-                let xsize = length (((cubes g) !! k) !! j) in
-                  if i >= xsize then
-                    error "i >= xsize in cube_at"
-                  else
-                    (((cubes g) !! k) !! j) !! i
-
+    | i < 0      = error "i < 0 in cube_at"
+    | i >= xsize = error "i >= xsize in cube_at"
+    | j < 0      = error "j < 0 in cube_at"
+    | j >= ysize = error "j >= ysize in cube_at"
+    | k < 0      = error "k < 0 in cube_at"
+    | k >= zsize = error "k >= zsize in cube_at"
+    | otherwise = (cubes g) ! (i,j,k)
+      where
+        fvs = function_values g
+        (xsize, ysize, zsize) = dims fvs
 
 --   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.
@@ -93,7 +98,8 @@ 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
+    | coord < offset = 0
+    | coord == offset && (xsize > 1 && ysize > 1 && zsize > 1) = 1
     | otherwise = (ceiling ( (coord + offset) / cube_width )) - 1
     where
       (xsize, ysize, zsize) = dims (function_values g)
@@ -124,9 +130,10 @@ zoom_result :: Grid -> ScaleFactor -> R.DIM3 -> Double
 zoom_result g (sfx, sfy, sfz) (R.Z R.:. i R.:. j R.:. k) =
   f p
   where
-    i' = (fromIntegral i) / (fromIntegral sfx)
-    j' = (fromIntegral j) / (fromIntegral sfy)
-    k' = (fromIntegral k) / (fromIntegral sfz)
+    offset = (h g)/2
+    i' = (fromIntegral i) / (fromIntegral sfx) - offset
+    j' = (fromIntegral j) / (fromIntegral sfy) - offset
+    k' = (fromIntegral k) / (fromIntegral sfz) - offset
     p  = (i', j', k') :: Point
     c = find_containing_cube g p
     t = find_containing_tetrahedron c p