Prop reification/splitting

src/Dodge/LinearShockwave/Draw.hs

@@ -0,0 +1,34 @@
+module Dodge.LinearShockwave.Draw
+    where
+import Geometry.Vector
+import Geometry.Data
+import ListHelp
+import Dodge.Data.LinearShockwave
+import Picture
+
+import Data.Maybe
+
+drawLinearShockwave :: LinearShockwave -> Picture
+drawLinearShockwave lw = setLayer BloomLayer $ setDepth 20 $ pictures $
+    theArc ++
+    [ lineCol $ zip (reverse lps) $ map (`withAlpha` white) [0,0.05..]
+    , lineCol $ zip (reverse rps) $ map (`withAlpha` white) [0,0.05..]
+    ]
+  where
+-- drawing half a circle here is not perfect, a slightly smaller arc would fit
+-- better, but this depends upon the angle formed by the following lines, which
+-- is not fixed (it varies with speed and angle of last turn)
+    theArc = maybeToList $ do
+        (hp,hv) <- safeHead pvs
+        r <- safeHead xs
+        return $ color (snd $ last lpairs) $ uncurryV translate hp 
+            $ arc (argV hv - pi/2) (argV hv + pi/2) $ r * magV hv
+    cols = map (`withAlpha` white) [0,0.05..]
+    lpairs = zip (reverse lps) cols
+    pvs = _lwPoints lw
+    t = _lwTimer lw
+    xs = take t $ drop (20 - t) [1,1.2..]
+    lps = zipWith f pvs xs
+    rps = zipWith g pvs xs
+    f (p,v) x = p  +.+ x *.* vNormal v
+    g (p,v) x = p  -.- x *.* vNormal v