we_env/init.lua

local mh = worldedit.manip_helpers

assert(worldedit.register_command,
	"Your WorldEdit installation is out of date, "..
	"please update to the latest version from git"..
	"to run we_env.")

---------------------------------------------
-- manipulations
---------------------------------------------

local function fall(pos1, pos2)
	local pos1, pos2 = worldedit.sort_pos(pos1, pos2)
	local dim = vector.add(vector.subtract(pos2, pos1), 1)
	if dim.y == 1 then return 0 end

	local manip, area = mh.init(pos1, pos2)
	local data = manip:get_data()

	local count = 0
	local stride = {x=1, y=area.ystride, z=area.zstride}
	local offset = vector.subtract(pos1, area.MinEdge)
	local c_air = minetest.get_content_id("air")
	for x = 0, dim.x-1 do
		local index_x = offset.x + x + 1 -- +1 for 1-based indexing
		for z = 0, dim.z do
			local index_z = index_x + (offset.z + z) * stride.z

			local y = 0
			local fall_height = 0
			while y < dim.y do
				local index = index_z + (offset.y + y) * stride.y
				local ndef = minetest.registered_nodes[minetest.get_name_from_content_id(data[index])]
				local did_fall = false
				if ndef ~= nil then
					if ndef.groups.falling_node ~= nil and fall_height > 0 then
						-- move all nodes above down by `fall_height`
						-- FIXME: move meta & param2 too
						for y2 = y, dim.y-1 do
							local index2 = index_z + (offset.y + y2) * stride.y
							data[index2 - stride.y * fall_height] = data[index2]
							data[index2] = c_air
						end
						count = count + (dim.y - y)
						did_fall = true
					elseif not ndef.walkable then
						fall_height = fall_height + 1
					else -- walkable and won't fall
						fall_height = 0
					end
				end

				if did_fall then
					-- restart processing from node above the one that fell
					y = y - fall_height + 1
					fall_height = 0
				else
					y = y + 1
				end
			end
		end
	end

	mh.finish(manip, data)
	return count
end

local function populate(pos1, pos2)
	local pos1, pos2 = worldedit.sort_pos(pos1, pos2)
	local dim = vector.add(vector.subtract(pos2, pos1), 1)

	local manip, area = mh.init(pos1, pos2)
	local data = manip:get_data()

	local stride = {x=1, y=area.ystride, z=area.zstride}
	local offset = vector.subtract(pos1, area.MinEdge)

	local count = 0
	local c_air = minetest.get_content_id("air")
	local c_dirt = minetest.get_content_id("default:dirt")
	local c_grass = minetest.get_content_id("default:dirt_with_grass")
	local c_stone = minetest.get_content_id("default:stone")
	for x = 0, dim.x-1 do
		local index_x = offset.x + x + 1 -- +1 for 1-based indexing
		for z = 0, dim.z-1 do
			local index_z = index_x + (offset.z + z) * stride.z

			local y = dim.y-1
			local last_was_air = false
			local depth = 0
			while y >= 0 do
				local index = index_z + (offset.y + y) * stride.y
				if data[index] == c_dirt then
					depth = depth + 1
					if last_was_air then
						data[index] = c_grass
						count = count + 1
					elseif depth > 3 then
						data[index] = c_stone
						count = count + 1
					end
				else
					depth = 0
				end

				last_was_air = data[index] == c_air
				y = y - 1
			end
		end
	end

	mh.finish(manip, data)
	return count
end

local function ores(pos1, pos2, pretend_y, try)
	local pos1, pos2 = worldedit.sort_pos(pos1, pos2)
	local dim = vector.add(vector.subtract(pos2, pos1), 1)

	local manip, area = mh.init(pos1, pos2)
	local data = manip:get_data()

	local stride = {x=1, y=area.ystride, z=area.zstride}
	local offset = vector.subtract(pos1, area.MinEdge)

	-- find out which ores we want
	local disallow_oretypes = {"sheet", "blob", "stratum"}
	local oreids = {}
	for _, def in pairs(minetest.registered_ores) do
		if table.indexof(disallow_oretypes, def.ore_type) == -1 then
			oreids[minetest.get_content_id(def.ore)] = true
		end
	end

	-- create a second manip
	local voff = vector.new(0, 0, 0)
	voff.x = area.MinEdge.x - math.random(-512, 512)*16
	voff.y = area.MinEdge.y - math.floor(pretend_y/16)*16 -- ensure same alignment(!)
	voff.z = area.MinEdge.z - math.random(-512, 512)*16
	local manip2 = VoxelManip(vector.subtract(area.MinEdge, voff), vector.subtract(area.MaxEdge, voff))

	-- copy data & generate ores inside that
	local data2 = manip2:get_data()
	for i = 1, area:getVolume() do
		data2[i] = data[i]
	end
	manip2:set_data(data2)

	local tmp1, tmp2 = manip2:get_emerged_area()
	minetest.generate_ores(manip2, tmp1, tmp2) -- nothing works if you omit the last two params

	-- apply the changes we want
	local count = 0
	manip2:get_data(data2)
	for x = 0, dim.x-1 do
		local index_x = offset.x + x + 1 -- +1 for 1-based indexing
		for y = 0, dim.y-1 do
			local index_y = index_x + (offset.y + y) * stride.y
			for z = 0, dim.z-1 do
				local index_z = index_y + (offset.z + z) * stride.z
				local cid = data2[index_z]
				if oreids[cid] then
					data[index_z] = cid
					count = count + 1
				end
			end
		end
	end

	-- looks like we hit some biome that didn't have ores
	try = try or 1
	if count == 0 and try < 4 then
		return ores(pos1, pos2, pretend_y, try + 1) -- try again
	end

	mh.finish(manip, data)
	return count
end

local print2d = function(name, w, h, max, index) -- for debugging
	local s = "##" .. name .. "\n" .. w .. "," .. h .. ":"
	for y = 0, h-1 do
	for x = 0, w-1 do
		local n = (1 - index(x, y) / max) * 255
		assert(n >= 0 and n <= 255)
		s = s .. string.format("%02x", math.floor(n))
	end
	end
	print(s)
end

local EWMA_alpha = 0.45
local WEIGHT = {orig=0.2, x=0.4, z=0.4}
local ewma = function(heightmap, hstride, dim, out)
	-- calculate EWMA for each x/z slice
	local slice_x, slice_z = {}, {}
	for x = 0, dim.x-1 do -- x+
		local res = {}
		local last = heightmap[x + 1]
		res[1] = last
		for z = 1, dim.z-1 do
			local h = heightmap[x + (z * hstride.z) + 1]
			last = EWMA_alpha * h + (1 - EWMA_alpha) * last
			res[z+1] = last
		end
		slice_x[x+1] = res
	end
	for x = 0, dim.x-1 do -- x- & averaging
		local res = slice_x[x+1]
		local last = heightmap[x + ((dim.z-1) * hstride.z) + 1]
		res[dim.z] = (res[dim.z] + last) / 2
		for z = dim.z-2, 0, -1 do
			local h = heightmap[x + (z * hstride.z) + 1]
			last = EWMA_alpha * h + (1 - EWMA_alpha) * last
			res[z+1] = (res[z+1] + last) / 2
		end
	end
	for z = 0, dim.z-1 do -- z+
		local res = {}
		local last = heightmap[(z * hstride.z) + 1]
		res[1] = last
		for x = 1, dim.x-1 do
			local h = heightmap[x + (z * hstride.z) + 1]
			last = EWMA_alpha * h + (1 - EWMA_alpha) * last
			res[x+1] = last
		end
		slice_z[z+1] = res
	end
	for z = 0, dim.z-1 do -- z- & averaging
		local res = slice_z[z+1]
		local last = heightmap[dim.x-1 + (z * hstride.z) + 1]
		res[dim.x] = (res[dim.x] + last) / 2
		for x = dim.x-2, 0, -1 do
			local h = heightmap[x + (z * hstride.z) + 1]
			last = EWMA_alpha * h + (1 - EWMA_alpha) * last
			res[x+1] = (res[x+1] + last) / 2
		end
	end

	--[[print2d("heightmap", dim.x, dim.z, dim.y, function(x, z)
		return heightmap[x + (z * hstride.z) + 1]
	end)
	print2d("ewma_x", dim.x, dim.z, dim.y, function(x, z)
		return slice_x[x+1][z+1]
	end)
	print2d("ewma_z", dim.x, dim.z, dim.y, function(x, z)
		return slice_z[z+1][x+1]
	end)--]]

	-- calculate actual heights
	for x = 0, dim.x-1 do
		for z = 0, dim.z-1 do
			local hindex = x + (z * hstride.z) + 1

			local old_height = heightmap[hindex]
			local new_height = math.floor(
				old_height * WEIGHT.orig +
				slice_x[x+1][z+1] * WEIGHT.x +
				slice_z[z+1][x+1] * WEIGHT.z +
				0.5
			)
			out[hindex] = new_height
		end
	end
end

local function smooth(pos1, pos2, deadzone, iterations)
	local pos1, pos2 = worldedit.sort_pos(pos1, pos2)
	local dim = vector.add(vector.subtract(pos2, pos1), 1)
	if dim.x < 2 or dim.y < 2 or dim.z < 2 then return 0 end

	local manip, area = mh.init(pos1, pos2)
	local data = manip:get_data()

	local stride = {x=1, y=area.ystride, z=area.zstride}
	local offset = vector.subtract(pos1, area.MinEdge)
	local c_air = minetest.get_content_id("air")
	local c_dirt = minetest.get_content_id("default:dirt")

	-- read heightmap from data
	local heightmap = {}
	local hstride = {x=1, z=dim.x}
	for x = 0, dim.x-1 do
		for z = 0, dim.z-1 do
			heightmap[x + (z * hstride.z) + 1] = 0
		end
	end
	for x = 0, dim.x-1 do
		local index_x = offset.x + x + 1 -- +1 for 1-based indexing
		for z = 0, dim.z-1 do
			local index_z = index_x + (offset.z + z) * stride.z

			local y = dim.y-1
			while y >= 0 do
				if data[index_z + (offset.y + y) * stride.y] ~= c_air then
					heightmap[x + (z * hstride.z) + 1] = y + 1
					break
				end
				y = y - 1
			end
		end
	end

	-- apply algorithm
	local heightmap_new = {}
	ewma(heightmap, hstride, dim, heightmap_new)
	for i = 2, iterations do
		ewma(heightmap_new, hstride, dim, heightmap_new)
	end

	-- adjust actual heights
	local count = 0
	for x = 0, dim.x-1 do
		local index_x = offset.x + x + 1 -- +1 for 1-based indexing
		for z = 0, dim.z-1 do
			local index_z = index_x + (offset.z + z) * stride.z

			local noop = false
			if x < deadzone.x or x > dim.x-1 - deadzone.x then noop = true end
			if z < deadzone.z or z > dim.z-1 - deadzone.z then noop = true end

			local hindex = x + (z * hstride.z) + 1
			local old_height = heightmap[hindex]
			local new_height = heightmap_new[hindex]

			if noop then
				-- do nothing (deadzone)
			elseif old_height > new_height then
				-- need to delete nodes
				local y = old_height-1
				while y >= new_height do
					local index = index_z + (offset.y + y) * stride.y
					if data[index] ~= c_air then data[index] = c_air end

					count = count + 1
					y = y - 1
				end
			elseif old_height < new_height then
				-- need to add nodes
				local c_top = c_dirt
				if old_height ~= 0 then
					c_top = data[index_z + (offset.y + old_height - 1) * stride.y]
				end

				local y = old_height
				while y <= new_height-1 do
					local index = index_z + (offset.y + y) * stride.y
					if data[index] == c_air then data[index] = c_top end

					count = count + 1
					y = y + 1
				end
			end
		end
	end

	mh.finish(manip, data)
	return count
end

---------------------------------------------
-- chat commands
---------------------------------------------

local check_region = function(name)
	return worldedit.volume(worldedit.pos1[name], worldedit.pos2[name])
end

worldedit.register_command("fall", {
	params = "",
	description = "Apply gravity to all falling nodes in selected region",
	privs = {worldedit=true},
	require_pos = 2,
	nodes_needed = check_region,
	func = function(name)
		local pos1, pos2 = worldedit.pos1[name], worldedit.pos2[name]
		local count = fall(pos1, pos2)
		worldedit.player_notify(name, count .. " nodes updated")
	end,
})

worldedit.register_command("populate", {
	params = "",
	description = "Populate dirt in selected region",
	privs = {worldedit=true},
	require_pos = 2,
	nodes_needed = check_region,
	func = function(name)
		local pos1, pos2 = worldedit.pos1[name], worldedit.pos2[name]
		local count = populate(pos1, pos2)
		worldedit.player_notify(name, count .. " nodes updated")
	end,
})

worldedit.register_command("ores", {
	params = "",
	description = "Generate ores in selected region",
	privs = {worldedit=true},
	require_pos = 2,
	nodes_needed = check_region,
	parse = function(param)
		return true, tonumber(param) or 0
	end,
	func = function(name, depth)
		local pos1, pos2 = worldedit.pos1[name], worldedit.pos2[name]
		local count = ores(pos1, pos2, depth)
		worldedit.player_notify(name, count .. " nodes updated")
	end,
})

worldedit.register_command("smooth", {
	params = "[iterations]",
	description = "Smooth terrain in selected region",
	privs = {worldedit=true},
	require_pos = 2,
	nodes_needed = check_region,
	parse = function(param)
		return true, tonumber(param) or 1
	end,
	func = function(name, iterations)
		local pos1, pos2 = worldedit.pos1[name], worldedit.pos2[name]
		local count = smooth(pos1, pos2, {x=0, z=0}, iterations)
		worldedit.player_notify(name, count .. " nodes updated")
	end,
})

---------------------------------------------
-- //smooth brush
---------------------------------------------

if minetest.registered_items["worldedit:brush"] == nil then
	minetest.after(0, function()
		minetest.log("error", "we_env: "..
			"worldedit_brush not installed or enabled, "..
			"brush functionality will be unavailable")
	end)
	return
end

local internal_name = "_smooth_brush_internal_do_not_use"
worldedit.register_command(internal_name, {
	params = "",
	privs = {worldedit=true},
	require_pos = 1,
	func = function(name)
		local pos = worldedit.pos1[name]

		-- Only modify an 10*10 area but take heights from 14*14 into consideration
		local dist, dead = 10, 4
		dist = dist + dead
		local pos1 = vector.apply(vector.subtract(pos, dist/2), math.floor)
		local pos2 = vector.add(pos1, dist)

		-- Expand region vertically to include lowest & highest nodes
		local max_height = 48
		max_height = math.floor(max_height / 2)
		pos1.y = pos.y - max_height -- defaults
		pos2.y = pos.y + max_height
		for y = pos.y, pos.y - max_height, -1 do
			local all_solid = true
			for x = pos1.x, pos2.x do
			for z = pos1.z, pos2.z do
				if minetest.get_node({x=x, y=y, z=z}).name == "air" then
					all_solid = false
					break
				end
			end
			end
			if all_solid then
				pos1.y = y
				break
			end
		end
		for y = pos.y, pos.y + max_height do
			local all_nonsolid = true
			for x = pos1.x, pos2.x do
			for z = pos1.z, pos2.z do
				if minetest.get_node({x=x, y=y, z=z}).name ~= "air" then
					all_nonsolid = false
					break
				end
			end
			end
			if all_nonsolid then
				pos2.y = y
				break
			end
		end

		smooth(pos1, pos2, {x=dead, z=dead}, 1)
		--[[worldedit.pos1[name] = pos1
		worldedit.pos2[name] = pos2
		worldedit.marker_update(name)--]]
	end,
})

worldedit.register_command("smoothbrush", {
	privs = {worldedit=true},
	params = "",
	description = "Assign smoothing action to WorldEdit brush item",
	func = function(name)
		local itemstack = minetest.get_player_by_name(name):get_wielded_item()
		if itemstack == nil or itemstack:get_name() ~= "worldedit:brush" then
			worldedit.player_notify(name, "Not holding brush item.")
			return
		end

		local meta = itemstack:get_meta()
		meta:set_string("command", internal_name)
		meta:set_string("params", "")
		meta:set_string("description",
			minetest.registered_tools["worldedit:brush"].description .. ": Smooth")
		worldedit.player_notify(name, "Smoothing action assigned to brush.")
		minetest.get_player_by_name(name):set_wielded_item(itemstack)
	end,
})