Correctly intersect lines and circles

src/Dodge/Item/Weapon/BatteryGuns.hs

@@ -166,15 +166,15 @@ aLaser it cr = particles .:~ makeLaserAt phasev pos dir
 makeLaserAt :: Float -> Point2 -> Float -> Particle
 makeLaserAt phasev pos dir = Particle
     { _ptDraw = const blank
-    , _ptUpdate = moveLaser phasev pos dir
+    , _ptUpdate = mvLaser phasev pos dir
     }
-moveLaser :: Float    -- ^ Phase velocity, controls deflection through windows
+mvLaser :: Float    -- ^ Phase velocity, controls deflection through windows
     -> Point2 
     -> Float 
     -> World 
     -> Particle 
     -> (World, Maybe Particle)
-moveLaser phasev pos dir w pt
+mvLaser phasev pos dir w pt
     = ( damThingHitWith (Lasering 19) pos xp thHit w
       , Just pt {_ptDraw = const pic ,_ptUpdate = ptSimpleTime 0 }
       )

src/Dodge/WorldEvent/ThingsHit.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE TupleSections #-}
 {- |
 Find which objects lie upon a line.
  -}
@@ -121,7 +122,10 @@ thingsHitLongLine sp ep w
     | sp == ep  = []
     | otherwise = sortOn (dist sp . fst) (crs ++  wls)
   where 
-    crs  = zip crPs (map Left hitCrs)
+    crs = mapMaybe 
+        (\cr -> (,Left cr) <$> listToMaybe (intersectCircSeg (_crPos cr) (_crRad cr) sp ep))
+        . IM.elems $ _creatures w
+    --crs  = zip crPs (map Left hitCrs)
     hitCrs = IM.elems 
         . IM.filter (\cr -> circOnSeg sp ep (_crPos cr) (_crRad cr))
         $ _creatures w

src/Geometry.hs

@@ -194,16 +194,6 @@ ssaTriPoint' pa pb pc' bc
         = Nothing
     | otherwise
         = Just $ ssaTriPoint pa pb pc' bc
--- | A potential correction of 'ssaTriPoint'.
--- This should be tested and benchmarked.
---ssaTriPointCorrect :: Point2 -> Point2 -> Point2 -> Float -> Maybe Point2
---ssaTriPointCorrect pa pb pc' bc
---    | param <= 1 && param >= 0 = Just p
---    | otherwise                = Nothing
---  where 
---    p = ssaTriPoint pa pb pc' bc
---    param = closestPointOnLineParam pa pc' p
-
 -- | Return Just a point if it is inside a circle, Nothing otherwise.
 pointInCircle :: Point2 -> Float -> Point2 -> Maybe Point2
 pointInCircle p r c 
@@ -223,9 +213,6 @@ collidePointCirc' p1 p2 rad c = fmap (\x -> magV (x -.- p1))
 collidePointCirc'' :: Point2 -> Point2 -> Float -> Point2 -> Maybe (Point2,Float)
 collidePointCirc'' p1 p2 rad c = (,) <$> collidePointCirc p1 p2 rad c
     <*>  collidePointCirc' p1 p2 rad c
--- | As 'collidePointCirc', but uses the supposedly correct version of ssaTriPoint.
---collidePointCircCorrect :: Point2 -> Point2 -> Float -> Point2 -> Maybe Point2
---collidePointCircCorrect p1 p2 rad c = ssaTriPointCorrect p2 c p1 rad
 -- | Finds the height of a triangle using herons formula.
 -- The base is the line between the first two points.
 heron :: Point2 -> Point2 -> Point2 -> Float

src/Geometry/Intersect.hs

@@ -251,10 +251,16 @@ orthogonalPointOnSeg a b p
     | otherwise              = Just $ a +.+ param *.* (normalizeV $ b -.- a)
   where
     param = closestPointOnLineParam a b p
+
+inSegArea :: Point2 -> Point2 -> Point2 -> Bool
+inSegArea a b c = param >= 0 && param <= dotV (b -.- a) (b -.- a)
+  where
+    param = dotV (b -.- a) (c -.- a)
+
 intersectCircSeg :: Point2 -> Float -> Point2 -> Point2 -> [Point2]
 intersectCircSeg c r a b 
     | y < 0 = []
-    | otherwise = nub $ filter ( (< dist a b) . dist a ) [ d -.- v, d +.+ c ]
+    | otherwise = nub $ filter (inSegArea a b) [ d -.- v, d +.+ c ]
   where
     d = closestPointOnLine a b c
     x = dist d c