Improve cactus drops and spawning (#4581)

- breaking cactus will drop randomly in x=-0.75..+0.75, z=-0.75..+0.75
- breaking cactus will have an initial velocity in this direction
- if a larger cactus break, they break into the same direction
- cactus growth rate reduced 4x, to debuff farm efficiency (will need a larger rebalancing)
- cactus only spawns when there is air surrounding it and above, so it does not immediately break
- slightly increase the frequency of cactus to counter this

The first changes make cactus farms possible.

Reviewed-on: VoxeLibre/VoxeLibre#4581
Reviewed-by: Mikita Wiśniewski <rudzik8@protonmail.com>
Co-authored-by: kno10 <erich.schubert@gmail.com>
Co-committed-by: kno10 <erich.schubert@gmail.com>

mods/ITEMS/mcl_core/functions.lua

@@ -191,12 +191,16 @@ minetest.register_abm({
 	nodenames = {"mcl_core:cactus"},
 	neighbors = {"group:sand"},
 	interval = 25,
-	chance = 10,
+	chance = 40,
 	action = function(pos)
 		mcl_core.grow_cactus(pos)
 	end,
 })
 
+local function is_walkable(pos)
+	local ndef = minetest.registered_nodes[minetest.get_node(pos).name]
+	return ndef and ndef.walkable
+end
 minetest.register_abm({
 	label = "Cactus mechanisms",
 	nodenames = {"mcl_core:cactus"},
@@ -209,18 +213,21 @@ minetest.register_abm({
 				object:remove()
 			end
 		end
-		local posses = { { 1, 0 }, { -1, 0 }, { 0, 1 }, { 0, -1 } }
+		if is_walkable(vector.offset(pos,  1, 0,  0))
-		for _, p in pairs(posses) do
+		or is_walkable(vector.offset(pos, -1, 0,  0))
-			local ndef = minetest.registered_nodes[minetest.get_node(vector.new(pos.x + p[1], pos.y, pos.z + p[2])).name]
+		or is_walkable(vector.offset(pos,  0, 0,  1))
-			if ndef and ndef.walkable then
+		or is_walkable(vector.offset(pos,  0, 0, -1)) then
-				local posy = pos.y
+			local lpos = vector.copy(pos)
-				while minetest.get_node(vector.new(pos.x, posy, pos.z)).name == "mcl_core:cactus" do
+			local dx, dy
-					local pos = vector.new(pos.x, posy, pos.z)
+			while true do
-					minetest.dig_node(pos)
+				local node = minetest.get_node(lpos)
-					-- minetest.add_item(vector.offset(pos, math.random(-0.5, 0.5), 0, math.random(-0.5, 0.5)), "mcl_core:cactus")
+				if not node or node.name ~= "mcl_core:cactus" then break end
-					posy = posy + 1
+				minetest.dig_node(lpos)
-				end
+				dx = dx or ((math.random(0,1)-0.5) * math.sqrt(math.random())) * 1.5
-				break
+				dy = dy or ((math.random(0,1)-0.5) * math.sqrt(math.random())) * 1.5
+				local obj = minetest.add_item(vector.offset(lpos, dx, 0.25, dy), "mcl_core:cactus")
+				obj:set_velocity(vector.new(dx, 1, dy))
+				lpos.y = lpos.y + 1
 			end
 		end
 	end,

mods/MAPGEN/mcl_biomes/init.lua

@@ -4656,9 +4656,9 @@ local function register_decorations()
 		place_on = {"group:sand"},
 		sidelen = 16,
 		noise_params = {
-			offset = -0.012,
+			offset = -0.01,
 			scale = 0.024,
-			spread = {x = 100, y = 100, z = 100},
+			spread = vector.new(100, 100, 100),
 			seed = 257,
 			octaves = 3,
 			persist = 0.6
@@ -4672,6 +4672,9 @@ local function register_decorations()
 				  "MesaPlateauFM", "MesaPlateauFM_sandlevel"},
 		height = 1,
 		height_max = 3,
+		spawn_by = "air",
+		check_offset = 1,
+		num_spawn_by = 16
 	})
 
 	-- Sugar canes