Digital line zoning

src/Geometry/Zone.hs

@@ -3,8 +3,12 @@ module Geometry.Zone
     ( ddaExt
     , ddaExt'
     , ddaSq
-    , ddaSqStream
+--    , ddaSqStream
     , ddaStream
+    , ddaStreamX
+    , ddaStreamY
+    , xIntercepts
+    , yIntercepts
     ) where
 import Geometry.Data
 
@@ -13,6 +17,7 @@ import qualified Streaming.Prelude as S
 import Data.Foldable
 import qualified Data.IntMap.Strict as IM
 import qualified Data.IntSet as IS
+--import Control.Monad
 
 --foldl2'
 --    :: (b -> a -> a -> b) 
@@ -62,6 +67,17 @@ divTo :: Float -> Float -> Int
 {-# INLINE divTo #-}
 divTo s = floor . (/s)
 
+modTo :: Float -> Float -> Float
+modTo s x = x - s * fromIntegral (divTo s x)
+
+--remTo :: Float -> Float -> Float
+--remTo s x = x - s * fromIntegral (quotTo s x)
+--
+--quotTo :: Float -> Float -> Int
+--{-# INLINE quotTo #-}
+--quotTo s = truncate . (/s)
+
+
 --flipV :: Point2 -> Point2
 --{-# INLINE flipV #-}
 --flipV (V2 a b) = V2 b a
@@ -93,13 +109,13 @@ ddaSq s (V2 sx sy) (V2 ex ey) = IM.fromSet (const ys) xs
     xs = IS.fromDistinctAscList [minx-1..maxx+1]
     ys = IS.fromDistinctAscList [miny-1..maxy+1]
 
-ddaSqStream :: Monad m => Float -> V2 Float -> V2 Float -> Stream (Of (Int,Int)) m ()
-ddaSqStream s (V2 sx sy) (V2 ex ey) = S.each [(x,y) | x <- [minx..maxx], y <- [miny..maxy]]
-  where
-    maxMin a b | a >= b = (a,b)
-        | otherwise = (b,a)
-    (maxx,minx) = maxMin (divTo s sx) (divTo s ex)
-    (maxy,miny) = maxMin (divTo s sy) (divTo s ey)
+--ddaSqStream :: Monad m => Float -> V2 Float -> V2 Float -> Stream (Of (V2 Int)) m ()
+--ddaSqStream s (V2 sx sy) (V2 ex ey) = S.each [V2 x y | x <- [minx..maxx], y <- [miny..maxy]]
+--  where
+--    maxMin a b | a >= b = (a,b)
+--        | otherwise = (b,a)
+--    (maxx,minx) = maxMin (divTo s sx) (divTo s ex)
+--    (maxy,miny) = maxMin (divTo s sy) (divTo s ey)
 
 -- | Determines which horizontal and vertical lines on a grid are crossed by a
 -- line. For each adds the x-y index of the square to the right or above the
@@ -129,8 +145,35 @@ ddaExt' s sp@(V2 sx sy) ep@(V2 ex ey)
         | otherwise = zip (map (divTo s) [y2x,y2x+xdy..])
                          [y2-1 .. y1-1] 
 ddaStream :: Float -> Point2 -> Point2 -> Stream (Of (V2 Int)) Identity ()
-ddaStream s sp _ -- @(V2 sx sy) ep@(V2 ex ey) 
-    = S.yield $ sizeZoneOfPoint' s sp
+ddaStream s sp ep = S.map (sizeZoneOfPoint' s)
+    $  S.yield sp
+    <> xIntercepts s sp ep
+    <> yIntercepts s sp ep
+
+ddaStreamX :: Float -> Point2 -> Point2 -> Stream (Of (V2 Int)) Identity ()
+ddaStreamX s sp ep = S.map (sizeZoneOfPoint' s) $ xIntercepts s sp ep
+
+ddaStreamY :: Float -> Point2 -> Point2 -> Stream (Of (V2 Int)) Identity ()
+ddaStreamY s sp ep = S.map (sizeZoneOfPoint' s) $ yIntercepts s sp ep
+
+xIntercepts :: Float -> Point2 -> Point2 -> Stream (Of Point2) Identity ()
+xIntercepts s (V2 sx sy) (V2 ex ey) 
+    | xdx == 0  = mempty
+    | xdx > 0   = S.each $ zipWith V2 [sx',sx'+xdx*50..ex] [sy',sy'+ydx*50..ey]
+    | otherwise = S.each $ zipWith V2 [sx'-50,sx'+xdx*50-50..ex-50] [sy',sy'+ydx*50..ey]
+  where
+    xdx = signum (ex - sx)
+    ydx = (ey - sy) / abs (ex - sx)
+
+    sy' = sy + ydx * abs (sx - sx')
+    sx' | xdx < 0 = sx - modTo s sx
+        | otherwise = s + sx - modTo s sx
+
+yIntercepts :: Float -> Point2 -> Point2 -> Stream (Of Point2) Identity ()
+yIntercepts s sp ep = S.map f $ xIntercepts s (f sp) (f ep)
+  where
+    f (V2 x y) = V2 y x
+
 
 -- | Determines which horizontal and vertical lines on a grid are crossed by a
 -- line. For each adds the x-y index of the square to the right or above the