Work towards convex partition of polygons

src/Dodge/Room/Tutorial.hs

@@ -238,10 +238,12 @@ sqPlatformChasm b a =
 
 sqSpitChasm :: Float -> Float -> ([[Point2]], [[Point2]])
 sqSpitChasm b a =
-    ( [[ibr, obr, otr, itr], [itr, otr, otl, itl], [itl, otl, obl, ibl]]
-    , [[ibr, obr, otr, otl, obl, ibl, itl, itr]]
+    ( --[[ibr, obr, otr, itr], [itr, otr, otl, itl], [itl, otl, obl, ibl]]
+        convexPartition clfs
+    , [clfs]
     )
   where
+    clfs = [ibr, obr, otr, otl, obl, ibl, itl, itr]
     obr = V2 a (-a)
     obl = V2 (-a) (-a)
     otl = V2 (-a) a
@@ -250,6 +252,12 @@ sqSpitChasm b a =
     ibl = V2 (-b) (-a)
     itl = V2 (-b) b
     itr = V2 b b
+--  otl---------otr
+--  |   itl-itr   |
+--  obr-ibl ibr-obl
+
+nonConvexChasm :: [Point2] -> PSType
+nonConvexChasm ps = PutChasm [] [ps]
 
 midChasmSpit :: State LayoutVars Room
 midChasmSpit = do
@@ -300,13 +308,14 @@ chasmSpitTerminal = do
          , [spanLightI (V2 0 128) (V2 300 128)]
          , [spanLightI (V2 300 0) (V2 0 300), sps0 $ putShape $ thinHighBar 95 0 300]
         ]
-    gh <- takeOne [55,97]
+    gh <- takeOne [55,75,97]
     gird <- takeOne [girderZ gh 30 10,girder gh 30 10,girderV gh 30 10]
     dec <- takeOne $ -- replicate 3 [] <> 
-            [
-            [sps0 $ putShape $ gird (V2 30 0) (V2 30 300)
-            ,sps0 $ putShape $ gird (V2 270 0) (V2 270 300)]
-            ,[sps0 $ putShape $ gird (V2 0 20) (V2 300 20)]
+            [--[]
+--            ,[sps0 $ putShape $ gird (V2 30 0) (V2 30 300)
+--            ,sps0 $ putShape $ gird (V2 270 0) (V2 270 300)]
+--            ,[sps0 $ putShape $ gird (V2 0 20) (V2 300 20)]
+            [sps0 $ putShape $ gird (V2 0 200) (V2 300 200)]
             ]
     -- let y' = y & rmPmnts <>~ [l3, l4, l5]
     let y' = y & rmPmnts <>~ ls <> dec

src/Geometry/Polygon.hs

@@ -151,6 +151,14 @@ convexHull :: [Point2] -> [Point2]
 convexHull (x : y : z : xs) = grahamScan $ orderAroundFirst $ sortOn (\(V2 a b) -> (b, a)) (x : y : z : xs)
 convexHull _ = error "Tried to create the convex hull of two or fewer points"
 
+-- assumes the points go "anticlockwise" around a non-self intersecting shape
+convexPartition :: [Point2] -> [[Point2]]
+convexPartition (x:y:z:[]) = [[x,y,z]]
+convexPartition (x:y:z:xs)
+    | isLHS x y z = [x,y,z] : convexPartition (x:z:xs)
+    | otherwise = convexPartition (y:z:xs <> [x])
+convexPartition _ = error "unexpected shape for convexPartition"
+
 {- | Creates the convex hull of a set of points.
  assumes no repetition of points: try nubbing!
 -}