1 files changed, 26 insertions, 0 deletions

diff --git a/Spear/Math/Sphere.hs b/Spear/Math/Sphere.hs
new file mode 100644
index 0000000..9c80811
--- /dev/null
+++ b/Spear/Math/Sphere.hs
@@ -0,0 +1,26 @@
+module Spear.Math.Sphere
+where
+
+import Spear.Math.Vector
+
+import Data.List (foldl')
+
+-- | A sphere in 3D space.
+data Sphere = Sphere
+    { center :: {-# UNPACK #-} !Vector3
+    , radius :: {-# UNPACK #-} !Float
+    }
+
+-- | Create a sphere from the given points.
+sphere :: [Vector3] -> Sphere
+sphere [] = Sphere zero3 0
+sphere (x:xs) = Sphere c r
+    where
+        c = pmin + (pmax-pmin)/2
+        r = norm $ pmax - c
+        (pmin,pmax) = foldl' update (x,x) xs
+        update (pmin,pmax) p = (min p pmin, max p pmax)
+
+-- | Return 'True' if the given sphere contains the given point, 'False' otherwise.
+circlept :: Sphere -> Vector3 -> Bool
+circlept (Sphere c r) p = r*r >= normSq (p - c)