implement own rotation and translation of hitboxes

these functions replace our usage of the Rotate and Translate
constructors of gloss. these were fine, but only for rendering.
since we want to do proper collision detection we had to
manually implement rotation and translation.

2 files changed, 23 insertions, 11 deletions

diff --git a/lib/Grav2ty/Simulation.hs b/lib/Grav2ty/Simulation.hs
index 65ab83d..1027d3f 100644
--- a/lib/Grav2ty/Simulation.hs
+++ b/lib/Grav2ty/Simulation.hs
@@ -1,6 +1,7 @@
 module Grav2ty.Simulation where
 
 import Control.Lens
+import Data.Complex
 import Linear.Matrix
 import Linear.Metric (norm, distance)
 import Linear.V2
@@ -27,6 +28,25 @@ shipHitbox = HCombined
 centeredCircle :: Num a => a -> Hitbox a
 centeredCircle r = HCircle (V2 0 0) r
 
+translateHitbox :: Num a => V2 a -> Hitbox a -> Hitbox a
+translateHitbox t (HLine a b) = HLine (a + t) (b + t)
+translateHitbox t (HCircle c r) = HCircle (c + t) r
+translateHitbox t (HCombined hs) = HCombined . map (translateHitbox t) $ hs
+
+complexV2 :: Iso' (Complex a) (V2 a)
+complexV2 = iso (\(x :+ y) -> V2 x y) (\(V2 x y) -> x :+ y)
+
+-- TODO address inaccuracies of 'Float' and 'Double'?
+-- | Rotate a 'Hitbox' by a radial angle.
+rotateHitbox :: RealFloat a => a -> Hitbox a -> Hitbox a
+rotateHitbox angle box =
+  case box of
+    HLine a b -> HLine (rotate a) (rotate b)
+    HCircle c r -> HCircle (rotate c) r
+    HCombined l -> HCombined . map (rotateHitbox angle) $ l
+  where rotator = cos angle :+ sin angle
+        rotate = (^. complexV2) . (* rotator) . (^. from complexV2)
+
 -- | Based on <https://de.wikipedia.org/wiki/Cramersche_Regel>
 cramer2 :: (Eq a, Fractional a) => M22 a -> V2 a -> Maybe (a, a)
 cramer2 coeff res = if detA == 0
diff --git a/src/Main.hs b/src/Main.hs
index 1fe67f5..fcbf244 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -34,20 +34,12 @@ renderHitbox box =  Color white $
     HCombined boxes -> Pictures $ map renderHitbox boxes
 
 renderObject :: Object Float -> Picture
-renderObject obj = translate x y . rot . renderHitbox . objectHitbox $ obj
-  where (V2 x y)  = objectLoc obj
-        rot       =  rotate (clockwise . toDegree . objectRot $ obj)
+renderObject obj = renderHitbox . translate . rot . objectHitbox $ obj
+  where translate = translateHitbox (objectLoc obj)
+        rot       = rotateHitbox (objectRot obj)
         toDegree  = (*) (360 / (2 * pi))
         clockwise = (*) (-1)
 
-renderObjectsCenter :: World Float -> ([Picture], Maybe (Float, Float))
-renderObjectsCenter w = accum w ([], Nothing)
-  where isLocal Dynamic { objectMod = LocalMod } = True
-        isLocal _ = False
-        accum [] acc = acc
-        accum (w:ws) (l, c) = accum ws
-          (renderObject w : l, if isLocal w then Just (vectorToPoint (objectLoc w)) else c)
-
 renderUi :: (Show a, Num a) => State a GlossState -> Picture
 renderUi state = (uncurry translate) (tupleMap ((+ 50) . (* (-1)) . (/ 2) . fromIntegral)
     . glossViewPort . graphics $ state)