Work on crab feet

src/Dodge/Creature/Picture.hs

@@ -69,7 +69,7 @@ drawHoverCrit cr = colorSH (_skinHead cskin)
 drawCrabCrit :: World -> Creature -> Shape
 drawCrabCrit w cr = mconcat 
     [ crabUpperBody w cr
-    , colorSH (_skinLower cskin) $ crabFeet cr
+    , colorSH (_skinLower cskin) $ crabFeet w cr
     ]
   where
     cskin = crShape $ _crType cr
@@ -169,27 +169,48 @@ feet cr = case (cr ^? crType . strideAmount,cr ^? crType . footForward) of
 --    f i = 8 * (sLen - 2*i) / sLen
     f i = 8 * oneSmooth ((sLen - 2*i) / sLen)
 
-crabFeet :: Creature -> Shape
+crabFeet :: World -> Creature -> Shape
 {-# INLINE crabFeet #-}
-crabFeet cr = 
-    uncurryV translateSHxy rpos afoot
-    <> uncurryV translateSHxy (f (V2 0 10) rpos) afoot
-    <> uncurryV translateSHxy lpos afoot
-    <> uncurryV translateSHxy (f (V2 0 (-10)) lpos) afoot
---    <> uncurryV translateSHxy (rotateV cdir $ cr ^?! crType . lFootPos - cxy) afoot
---    <> uncurryV translateSHxy (rotateV cdir $ cxy - cr ^?! crType . lFootPos) afoot
---    case (cr ^? crType . strideAmount,cr ^? crType . footForward) of
---    (Just sa,Just LeftForward) -> sh (f sa)
---    (Just sa,Just RightForward) -> sh (-f sa)
---    _ -> sh 0
+crabFeet _ cr = 
+    uncurryV translateSHxy rpos (afoot & each . sfVs . each %~ Q.rotate r1)
+    <> (afoot 
+        & each . sfVs . each %~ Q.rotate r2
+        & each . sfVs . each +~ V3 0 2 5)
+    <> uncurryV translateSHxy rpos' (afoot & each . sfVs . each %~ Q.rotate r1')
+    <> (afoot 
+        & each . sfVs . each %~ Q.rotate r2'
+        & each . sfVs . each +~ V3 0 2 5)
+    <> uncurryV translateSHxy lpos (afoot & each . sfVs . each %~ Q.rotate l1)
+    <> (afoot 
+        & each . sfVs . each %~ Q.rotate l2
+        & each . sfVs . each +~ V3 0 (-2) 5)
+    <> uncurryV translateSHxy lpos' (afoot & each . sfVs . each %~ Q.rotate l1')
+    <> (afoot 
+        & each . sfVs . each %~ Q.rotate l2'
+        & each . sfVs . each +~ V3 0 (-2) 5)
   where
-    rpos = rot ( cr ^?! crType . rFootPos - cxy)
+    rpos = rot (cr ^?! crType . rFootPos - cxy)
     rot = rotateV cdir 
     lpos = rot ( cr ^?! crType . lFootPos - cxy)
     f p q = q + 2 *^ (p - q)
     cdir = -cr ^. crDir
     cxy = cr ^. crPos . _xy
     afoot = upperPrismPolyST 10 $ polyCirc 3 2
+    (r1,r2) = spiderJoint (0 & _xy .~ rpos) (V3 0 2 5)
+    rpos' = f (V2 0 10) rpos
+    (r1',r2') = spiderJoint (0 & _xy .~ rpos') (V3 0 2 5)
+    (l1,l2) = spiderJoint (0 & _xy .~ lpos) (V3 0 (-2) 5)
+    lpos' = (f (V2 0 (-10)) lpos)
+    (l1',l2') = spiderJoint (0 & _xy .~ lpos') (V3 0 (-2) 5)
+
+spiderJoint :: Point3 -> Point3 -> (Q.Quaternion Float, Q.Quaternion Float)
+spiderJoint p q = (f $ Q.axisAngle (V3 0 (-1) 0) (pi - (a+b)), f . Q.axisAngle (V3 0 (-1) 0) $ a - b)
+--spiderJoint p q = (Q.qz c, Q.axisAngle (V3 0 (-1) 0) $ a)
+  where
+    a = angleThreeSides 10 (distance p q) 10
+    b = angleVV3 (q-p) (V3 0 0 (-1))
+    c = argV $ (p-q) ^. _xy
+    f x = Q.qz c * x
 
 deadFeet :: Creature -> Shape
 {-# INLINE deadFeet #-}

src/Geometry/Vector.hs

@@ -67,6 +67,12 @@ angleVV a b
             d = a `dotV` b
          in acos $ d / (ma * mb)
 
+-- returns the angle opposite length a
+angleThreeSides :: Float -> Float -> Float -> Float
+angleThreeSides a b c = acos $ (f b + f c - f a) / (2*b*c)
+  where
+    f = (^ (2 ::Int))
+
 -- | Safe version of 'angleVV' that returns 0 if either vector is null.
 safeAngleVV :: Point2 -> Point2 -> Float
 {-# INLINE safeAngleVV #-}

src/Geometry/Vector3D.hs

@@ -1,6 +1,7 @@
 {-# LANGUAGE BangPatterns #-}
 module Geometry.Vector3D
     where
+import Linear
 import Geometry.Vector
 import Geometry.Data
 
@@ -121,7 +122,7 @@ dotV3 (V3 x y z) (V3 a b c) = x*a + y*b + z*c
 
 angleVV3 :: Point3 -> Point3 -> Float
 angleVV3 a b 
-    | a == b = 0
+    | a == b || norm a == 0 || norm b == 0 = 0
     | otherwise = acos $ dotV3 a b / (magV3 a * magV3 b)
 
 --projV3 :: Point3 -> Point3 -> Point3