Towards working shadows

src/Shader/Poke.hs

@@ -22,7 +22,6 @@ import qualified Data.Vector.Mutable as MV
 import qualified Data.Vector.Fusion.Stream.Monadic as VS
 import Control.Monad.Primitive
 import Control.Monad
-import Data.Bifoldable
 --import qualified Data.DList as DL
 
 pokeVerxs 
@@ -91,11 +90,13 @@ pokeTopPrismIndex nv iptr ni ioff = do
 topPrismEdgeIndices :: Int -> [Int]
 topPrismEdgeIndices n = concatMap f [0..n-1]
   where
-    f i = 
-        [ i, (i+2) `mod` n, i+1, (i+4) `mod` n
-        , i, i+1, (i+4) `mod` n, (i+3) `mod` n
-        , i+1, (i+5) `mod` n, i, (i+3) `mod` n
+    f i = map g
+        [ 0 , 2 , 1 , 4
+        , 0 , 1 ,-2 , 3
+        , 1 , 3 ,-1 , 2
         ]
+      where
+        g j = (2 * i + j) `mod` n
 
 topPrismIndices :: Int -> [Int]
 topPrismIndices n = concatMap f [1..n-2]    -- triangles on top face