improve grass growth.

grass now grows up and down diagonally in the cardinal directions.

mods/bg_grass/growth.lua

@@ -1,14 +1,47 @@
+-- TODO: move these to the general api.
+local function listify_table (tab)
+	local copy = {}
+	for _, item in pairs(tab) do
+		table.insert(copy, item)
+	end
+	return copy
+end
+local function shuffle (tab)
+	tab = listify_table(tab)
+
+	local shuffled = {}
+
+	repeat
+		local index = math.random(1, #tab)
+		local value = tab[index]
+		table.insert(shuffled, value)
+		table.remove(tab, index)
+	until #tab == 0
+
+	return shuffled
+end
+
 blockgame.register_abm({
 	nodenames = {"core:grass"},
 	neighbors = {"core:dirt"},
 	interval = 15,
 	chance = 8,
 	action = function (pos, node)
-		-- TODO: also check diagonally adjacent nodes?
-		-- TODO: shuffle sides; currently they grow in a specific order determined by the order of `blockgame.vector.sides`.
-		local sides = blockgame.vector.sides
+		local sides = listify_table(blockgame.vector.sides)
+		local diagonally = {}
+
 		for _, side in pairs(sides) do
-			if attempt_spread(pos + side) then return true end
+			table.insert(diagonally, side + blockgame.vector.dirs.down)
+			table.insert(diagonally, side + blockgame.vector.dirs.up)
+		end
+		sides = shuffle(sides)
+		diagonally = shuffle(diagonally)
+
+		for _, offset in pairs(sides) do
+			if attempt_spread(pos + offset) then return true end
+		end
+		for _, offset in pairs(diagonally) do
+			if attempt_spread(pos + offset) then return true end
 		end
 		return false
 	end,