Use some Linear library functions

src/Geometry/Intersect.hs

@@ -4,6 +4,8 @@
 {- Testing for and finding intersection points.  -}
 module Geometry.Intersect where
 
+import Linear
+import Control.Lens
 import Control.Applicative
 import Data.List
 import Data.Maybe
@@ -11,7 +13,6 @@ import Geometry.Data
 import Geometry.LHS
 import Geometry.Vector
 import Geometry.Vector3D
-import Linear.Metric
 import Control.Monad
 
 -- | If two lines intersect, return 'Just' that point.
@@ -219,8 +220,8 @@ myIntersectLineLine a@(V2 ax _) b c@(V2 cx _) d
             Just 0 -> Nothing
             _ -> liftA2 V2 newx ((linGrad a b ^*^ newx) ^+^ axisInt a b)
   where
-    (^-^) = liftA2 (-)
-    (^+^) = liftA2 (+)
+--    (^-^) = liftA2 (-)
+--    (^+^) = liftA2 (+)
     (^/^) = liftA2 (/)
     (^*^) = liftA2 (*)
     newx = (axisInt c d ^-^ axisInt a b) ^/^ (linGrad a b ^-^ linGrad c d)
@@ -348,8 +349,19 @@ intersectCircSeg c r a b
     z = sqrt y
     v = z *.* normalizeV (b -.- a)
 
-intersectCylSeg :: Point3 -> Float -> Float -> Point3 -> Point3 -> Maybe Point3
-intersectCylSeg p r h x y = Nothing
+intersectCircLineAlong :: Point2 -> Float -> Point2 -> Point2 -> Maybe (Float, Float)
+intersectCircLineAlong p r x y = do
+    let d = y - x
+        f = p - x
+        dis = (dot d f / dot d d) ** 2 + (dot f f - r ** 2)/dot d d
+    guard $ dis > 0
+    let a = dot d f / dot d d
+    return (a - dis, a + dis)
+
+intersectCylSeg :: Point3 -> Float -> Float -> Point3 -> Point3 -> Maybe (Point3, Point3)
+intersectCylSeg p r h x y = do
+    (a,b) <- intersectCircLineAlong (p ^. _xy) r (x ^. _xy) (y ^. _xy)
+    Nothing
 
 intersectCircSegTest :: Point2 -> Float -> Point2 -> Point2 -> Bool
 intersectCircSegTest c r x y = intersectSegSegTest (c + z) (c - z) x y