Work on gibs and chasms

src/Geometry/Intersect.hs

@@ -10,6 +10,9 @@ import Data.Maybe
 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.
 intersectLineLine' :: Point2 -> Point2 -> Point2 -> Point2 -> Maybe Point2
@@ -21,6 +24,33 @@ intersectLineLine' (V2 x1 y1) (V2 x2 y2) (V2 x3 y3) (V2 x4 y4)
     den = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4)
     t' = (x1 - x3) * (y3 - y4) - (y1 - y3) * (x3 - x4)
 
+-- note that the second argument is a vector, not the second point of the line
+intersectLinePlane :: Point3 -> Point3 -> Point3 -> Point3 -> Maybe Point3
+intersectLinePlane l v p n = case dot v n of
+    0 -> Nothing
+    x -> Just $ l + ((dot (p - l) n) / x) *.*.* v
+
+-- this needs to be checked
+intersectSegPlane :: Point3 -> Point3 -> Point3 -> Point3 -> Maybe Point3
+intersectSegPlane sp ep p n = case dot v n of
+    0 -> Nothing
+    x -> case dot (p - sp) n / x of
+        d | d >= 0 && d <= 1 -> Just $ sp + d *.*.* v
+        _ -> Nothing
+  where
+    v = ep - sp
+
+intersectSegSurface :: Point3 -> Point3 -> Point3 -> Point3 
+    -> [(Point3,Point3)] -> Maybe Point3
+intersectSegSurface sp ep p n ss = do
+    xp <- intersectSegPlane sp ep p n
+    let f (a,b) = isNHS a b xp
+    guard $ all f ss
+    return xp
+
+isNHS :: Point3 -> Point3 -> Point3 -> Bool
+isNHS p n x = 0 < dot n (x - p)
+
 intersectSegSegErrorTest :: Point2 -> Point2 -> Point2 -> Point2 -> Maybe Point2
 {-# INLINE intersectSegSegErrorTest #-}
 intersectSegSegErrorTest a b c d = case intersectSegSeg a b c d of