Add marram grass for coastal sand dunes

Use noise with 1 octave and flag 'absvalue' to create sand paths
in dunes.

mods/default/README.txt

@@ -114,6 +114,7 @@ paramat (CC BY-SA 3.0):
   default_silver_sandstone_brick.png -- Derived from a texture by GreenXenith (CC-BY-SA 3.0)
   default_silver_sandstone_block.png -- Derived from a texture by GreenXenith (CC-BY-SA 3.0)
   default_bookshelf_slot.png -- Derived from a texture by Gambit (CC-BY-SA 3.0)
+  default_marram_grass_*.png -- Derived from textures by TumeniNodes (CC-BY-SA 3.0)
 
 TumeniNodes (CC BY-SA 3.0):
   default_desert_cobble.png -- Derived from a texture by brunob.santos (CC BY-SA 3.0)

mods/default/crafting.lua

@@ -1104,6 +1104,12 @@ minetest.register_craft({
 	burntime = 2,
 })
 
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:marram_grass_1",
+	burntime = 2,
+})
+
 minetest.register_craft({
 	type = "fuel",
 	recipe = "default:paper",

mods/default/mapgen.lua

@@ -1603,7 +1603,7 @@ end
 local function register_grass_decoration(offset, scale, length)
 	minetest.register_decoration({
 		deco_type = "simple",
-		place_on = {"default:dirt_with_grass", "default:sand"},
+		place_on = {"default:dirt_with_grass"},
 		sidelen = 16,
 		noise_params = {
 			offset = offset,
@@ -1613,8 +1613,7 @@ local function register_grass_decoration(offset, scale, length)
 			octaves = 3,
 			persist = 0.6
 		},
-		biomes = {"grassland", "grassland_dunes", "deciduous_forest",
-			"coniferous_forest_dunes", "floatland_grassland"},
+		biomes = {"grassland", "deciduous_forest", "floatland_grassland"},
 		y_min = 1,
 		y_max = 31000,
 		decoration = "default:grass_" .. length,
@@ -2022,6 +2021,31 @@ function default.register_decorations()
 		param2 = 4,
 	})
 
+	-- Marram grass
+
+	minetest.register_decoration({
+		deco_type = "simple",
+		place_on = {"default:sand"},
+		sidelen = 4,
+		noise_params = {
+			offset = -0.4,
+			scale = 3.0,
+			spread = {x = 16, y = 16, z = 16},
+			seed = 513337,
+			octaves = 1,
+			persist = 0.5,
+			flags = "absvalue"
+		},
+		biomes = {"coniferous_forest_dunes", "grassland_dunes"},
+		y_min = 4,
+		y_max = 5,
+		decoration = {
+			"default:marram_grass_1",
+			"default:marram_grass_2",
+			"default:marram_grass_3",
+		},
+	})
+
 	-- Coral reef
 
 	minetest.register_decoration({

mods/default/nodes.lua

@@ -147,6 +147,10 @@ default:fern_1
 default:fern_2
 default:fern_3
 
+default:marram_grass_1
+default:marram_grass_2
+default:marram_grass_3
+
 default:bush_stem
 default:bush_leaves
 default:bush_sapling
@@ -1373,6 +1377,57 @@ for i = 2, 3 do
 end
 
 
+minetest.register_node("default:marram_grass_1", {
+	description = "Marram Grass",
+	drawtype = "plantlike",
+	waving = 1,
+	tiles = {"default_marram_grass_1.png"},
+	inventory_image = "default_marram_grass_1.png",
+	wield_image = "default_marram_grass_1.png",
+	paramtype = "light",
+	sunlight_propagates = true,
+	walkable = false,
+	buildable_to = true,
+	groups = {snappy = 3, flammable = 3, attached_node = 1},
+	sounds = default.node_sound_leaves_defaults(),
+	selection_box = {
+		type = "fixed",
+		fixed = {-6 / 16, -0.5, -6 / 16, 6 / 16, -0.25, 6 / 16},
+	},
+
+	on_place = function(itemstack, placer, pointed_thing)
+		-- place a random marram grass node
+		local stack = ItemStack("default:marram_grass_" .. math.random(1, 3))
+		local ret = minetest.item_place(stack, placer, pointed_thing)
+		return ItemStack("default:marram_grass_1 " ..
+			itemstack:get_count() - (1 - ret:get_count()))
+	end,
+})
+
+for i = 2, 3 do
+	minetest.register_node("default:marram_grass_" .. i, {
+		description = "Marram Grass",
+		drawtype = "plantlike",
+		waving = 1,
+		tiles = {"default_marram_grass_" .. i .. ".png"},
+		inventory_image = "default_marram_grass_" .. i .. ".png",
+		wield_image = "default_marram_grass_" .. i .. ".png",
+		paramtype = "light",
+		sunlight_propagates = true,
+		walkable = false,
+		buildable_to = true,
+		groups = {snappy = 3, flammable = 3, attached_node = 1,
+			not_in_creative_inventory=1},
+		drop = "default:marram_grass_1",
+		sounds = default.node_sound_leaves_defaults(),
+		selection_box = {
+			type = "fixed",
+			fixed = {-6 / 16, -0.5, -6 / 16, 6 / 16, -0.25, 6 / 16},
+		},
+	})
+end
+
+
 minetest.register_node("default:bush_stem", {
 	description = "Bush Stem",
 	drawtype = "plantlike",