Allow tweaking z buffer when rendering polygon, improve explosion render

src/Picture.hs

@@ -1,8 +1,11 @@
+{-# LANGUAGE TupleSections #-}
 module Picture
     ( module Picture.Data
     , polygon
+    , polygonZ
     , polygonCol
-    , poly3D
+    , poly3
+    , poly3Col
     , bezierQuad
     , arc
     , arcSolid
@@ -63,13 +66,21 @@ polygon :: [Point2] -> Picture
 {-# INLINE polygon #-}
 polygon = Polygon 0
 
+polygonZ :: [Point2] -> Float -> Picture
+{-# INLINE polygonZ #-}
+polygonZ = PolygonZ 0
+
 polygonCol :: [(Point2,RGBA)] -> Picture
 {-# INLINE polygonCol #-}
 polygonCol = PolygonCol 0
 
-poly3D :: [(Point3,RGBA)] -> Picture
-{-# INLINE poly3D #-}
-poly3D = Poly3D 0
+poly3 :: [Point3] -> Picture
+{-# INLINE poly3 #-}
+poly3 = poly3Col . map (, black)
+
+poly3Col :: [(Point3,RGBA)] -> Picture
+{-# INLINE poly3Col #-}
+poly3Col = Poly3D 0
 
 -- note that much of work computing the width of the bezier curve is done here
 bezierQuad :: Color -> Color -> Float -> Float -> Point2 -> Point2 -> Point2 -> Picture