Use biomegen.skip_chunk and place it before timer.

(latest version of biomegen)

README.md

@@ -17,7 +17,7 @@ Code: Gaël de Sailly
 Flow routing algorithm concept (in `terrainlib/rivermapper.lua`): Cordonnier, G., Bovy, B., & Braun, J. (2019). A versatile, linear complexity algorithm for flow routing in topographies with depressions. Earth Surface Dynamics, 7(2), 549-562.
 
 # Requirements
-Mod dependencies: `default` required, and [`biomegen`](https://github.com/Gael-de-Sailly/biomegen) optional (provides biome system).
+No required dependency, but [`biomegen`](https://gitlab.com/gaelysam/biomegen) recommended (provides biome system).
 
 # Installation
 This mod should be placed in the `mods/` directory of Minetest like any other mod.

compatibility.lua

@@ -1,3 +1,24 @@
+-- Fix compatibility for settings-related changes
+-- Only loaded if the versions of the mod and the world mismatch
+
+local function version_is_lower(v1, v2)
+	local d1, c1, d2, c2
+	while #v1 > 0 and #v2 > 0 do
+		d1, c1, v1 = v1:match("^(%d*)(%D*)(.*)$")
+		d2, c2, v2 = v2:match("^(%d*)(%D*)(.*)$")
+
+		d1 = tonumber(d1) or -1
+		d2 = tonumber(d2) or -1
+		if d1 ~= d2 then
+			return d1 < d2
+		end
+		if c1 ~= c2 then
+			return c1 < c2
+		end
+	end
+	return false
+end
+
 local function fix_min_catchment(settings, is_global)
 	local prefix = is_global and "mapgen_rivers_" or ""
 
@@ -21,6 +42,18 @@ local function fix_compatibility_minetest(settings)
 	if previous_version == "0.0" then
 		fix_min_catchment(settings, true)
 	end
+
+	if version_is_lower(previous_version, "1.0.2-dev1") then
+		local blocksize = tonumber(settings:get("mapgen_rivers_blocksize") or 15)
+		local grid_x_size = tonumber(settings:get("mapgen_rivers_grid_x_size"))
+		if grid_x_size then
+			settings:set("mapgen_rivers_map_x_size", tostring(grid_x_size * blocksize))
+		end
+		local grid_z_size = tonumber(settings:get("mapgen_rivers_grid_z_size"))
+		if grid_z_size then
+			settings:set("mapgen_rivers_map_z_size", tostring(grid_z_size * blocksize))
+		end
+	end
 end
 
 local function fix_compatibility_mapgen_rivers(settings)
@@ -29,6 +62,18 @@ local function fix_compatibility_mapgen_rivers(settings)
 	if previous_version == "0.0" then
 		fix_min_catchment(settings, false)
 	end
+
+	if version_is_lower(previous_version, "1.0.2-dev1") then
+		local blocksize = tonumber(settings:get("blocksize") or 15)
+		local grid_x_size = tonumber(settings:get("grid_x_size"))
+		if grid_x_size then
+			settings:set("map_x_size", tostring(grid_x_size * blocksize))
+		end
+		local grid_z_size = tonumber(settings:get("grid_z_size"))
+		if grid_z_size then
+			settings:set("map_z_size", tostring(grid_z_size * blocksize))
+		end
+	end
 end
 
 return fix_compatibility_minetest, fix_compatibility_mapgen_rivers

geometry.lua

@@ -1,40 +0,0 @@
-local sqrt, abs = math.sqrt, math.abs
-local unpk = unpack
-
-local function distance_to_segment(x1, y1, x2, y2, x, y)
-	-- get the distance between point (x,y) and segment (x1,y1)-(x2,y2)
-	local a = (x1-x2)^2 + (y1-y2)^2 -- square of distance
-	local b = (x1-x)^2 + (y1-y)^2
-	local c = (x2-x)^2 + (y2-y)^2
-	if a + b < c then
-		-- The closest point of the segment is the extremity 1
-		return sqrt(b)
-	elseif a + c < b then
-		-- The closest point of the segment is the extremity 2
-		return sqrt(c)
-	else
-		-- The closest point is on the segment
-		return abs(x1 * (y2-y) + x2 * (y-y1) + x * (y1-y2)) / sqrt(a)
-	end
-end
-
-local function transform_quadri(X, Y, x, y)
-	-- To index points in an irregular quadrilateral, giving x and y between 0 (one edge) and 1 (opposite edge)
-	-- X, Y 4-vectors giving the coordinates of the 4 vertices
-	-- x, y position to index.
-	local x1, x2, x3, x4 = unpk(X)
-	local y1, y2, y3, y4 = unpk(Y)
-
-	-- Compare distance to 2 opposite edges, they give the X coordinate
-	local d23 = distance_to_segment(x2,y2,x3,y3,x,y)
-	local d41 = distance_to_segment(x4,y4,x1,y1,x,y)
-	local xc = d41 / (d23+d41)
-
-	-- Same for the 2 other edges, they give the Y coordinate
-	local d12 = distance_to_segment(x1,y1,x2,y2,x,y)
-	local d34 = distance_to_segment(x3,y3,x4,y4,x,y)
-	local yc = d12 / (d12+d34)
-	return xc, yc
-end
-
-return transform_quadri

gridmanager.lua

@@ -0,0 +1,105 @@
+-- Manages grid loading, writing and generation
+
+local datapath = mapgen_rivers.world_data_path
+
+local registered_on_grid_loaded = {}
+function mapgen_rivers.register_on_grid_loaded(func)
+	if type(func) == "function" then
+		registered_on_grid_loaded[#registered_on_grid_loaded+1] = func
+	else
+		minetest.log("error", "[mapgen_rivers] register_on_grid_loaded can only register functions!")
+	end
+end
+
+local function on_grid_loaded_callback(grid)
+	for _, func in ipairs(registered_on_grid_loaded) do
+		func(grid)
+	end
+end
+
+local function offset_conv(o)
+	return (o + 0.5) * (1/256)
+end
+
+local floor = math.floor
+local sbyte, schar = string.byte, string.char
+local unpk = unpack
+
+-- Loading files
+
+-- Never load the full map during mapgen. Instead, create an empty lookup table
+-- and read the file on-the-fly when an element is requested for the first time,
+-- using __index metamethod.
+local loader_mt = {
+	__index = function(loader, i) -- Called when accessing a missing key
+		local file = loader.file
+		local bytes = loader.bytes
+		file:seek('set', (i-1)*bytes)
+		local strnum = file:read(bytes)
+
+		local n = sbyte(strnum, 1)
+		if loader.signed and n >= 128 then
+			n = n - 256
+		end
+
+		for j=2, bytes do
+			n = n*256 + sbyte(strnum, j)
+		end
+
+		if loader.conv then
+			n = loader.conv(n)
+		end
+		-- Cache key for next use
+		loader[i] = n
+		return n
+	end,
+}
+
+local function load_file(filename, bytes, signed, size, converter)
+	local file = io.open(datapath .. filename, 'rb')
+	if file then
+		converter = converter or false
+		return setmetatable({file=file, bytes=bytes, signed=signed, size=size, conv=converter}, loader_mt)
+	end
+end
+
+function mapgen_rivers.load_or_generate_grid()
+	-- First, check whether a grid is already loaded
+	if mapgen_rivers.grid then
+		return true
+	end
+
+	-- If not, try to load the grid from the files
+	local sfile = io.open(datapath .. 'size', 'r')
+	if not sfile then
+		dofile(mapgen_rivers.modpath .. "/pregenerate.lua")
+		collectgarbage()
+
+		sfile = io.open(datapath .. 'size', 'r')
+		if not sfile then
+			return false
+		end
+	end
+
+	local x, z = sfile:read('*n'), sfile:read('*n')
+	if not x or not z then
+		return false
+	end
+
+	minetest.log("action", '[mapgen_rivers] Loading grid')
+
+	local grid = {
+		size = {x=x, y=z},
+		dem = load_file('dem', 2, true, x*z),
+		lakes = load_file('lakes', 2, true, x*z),
+		dirs = load_file('dirs', 1, false, x*z),
+		rivers = load_file('rivers', 4, false, x*z),
+		offset_x = load_file('offset_x', 1, true, x*z, offset_conv),
+		offset_y = load_file('offset_y', 1, true, x*z, offset_conv),
+	}
+
+	mapgen_rivers.grid = grid
+	on_grid_loaded_callback(grid)
+
+	return true
+end

heightmap.lua

@@ -1,17 +1,53 @@
-local modpath = mapgen_rivers.modpath
+-- Transform polygon data into a heightmap
 
-local make_polygons = dofile(modpath .. 'polygons.lua')
-local transform_quadri = dofile(modpath .. 'geometry.lua')
+local modpath = mapgen_rivers.modpath
 
 local sea_level = mapgen_rivers.settings.sea_level
 local riverbed_slope = mapgen_rivers.settings.riverbed_slope * mapgen_rivers.settings.blocksize
 
-local MAP_BOTTOM = -31000
+local out_elev = mapgen_rivers.settings.margin_elev
 
 -- Localize for performance
-local floor, min, max = math.floor, math.min, math.max
+local floor, min, max, sqrt, abs = math.floor, math.min, math.max, math.sqrt, math.abs
 local unpk = unpack
 
+-- Geometrical helpers
+local function distance_to_segment(x1, y1, x2, y2, x, y)
+	-- get the distance between point (x,y) and segment (x1,y1)-(x2,y2)
+	local a = (x1-x2)^2 + (y1-y2)^2 -- square of distance
+	local b = (x1-x)^2 + (y1-y)^2
+	local c = (x2-x)^2 + (y2-y)^2
+	if a + b < c then
+		-- The closest point of the segment is the extremity 1
+		return sqrt(b)
+	elseif a + c < b then
+		-- The closest point of the segment is the extremity 2
+		return sqrt(c)
+	else
+		-- The closest point is on the segment
+		return abs(x1 * (y2-y) + x2 * (y-y1) + x * (y1-y2)) / sqrt(a)
+	end
+end
+
+local function transform_quadri(X, Y, x, y)
+	-- To index points in an irregular quadrilateral, giving x and y between 0 (one edge) and 1 (opposite edge)
+	-- X, Y 4-vectors giving the coordinates of the 4 vertices
+	-- x, y position to index.
+	local x1, x2, x3, x4 = unpk(X)
+	local y1, y2, y3, y4 = unpk(Y)
+
+	-- Compare distance to 2 opposite edges, they give the X coordinate
+	local d23 = distance_to_segment(x2,y2,x3,y3,x,y)
+	local d41 = distance_to_segment(x4,y4,x1,y1,x,y)
+	local xc = d41 / (d23+d41)
+
+	-- Same for the 2 other edges, they give the Y coordinate
+	local d12 = distance_to_segment(x1,y1,x2,y2,x,y)
+	local d34 = distance_to_segment(x3,y3,x4,y4,x,y)
+	local yc = d12 / (d12+d34)
+	return xc, yc
+end
+
 -- Linear interpolation
 local function interp(v00, v01, v11, v10, xf, zf)
 	local v0 = v01*xf + v00*(1-xf)
@@ -19,9 +55,9 @@ local function interp(v00, v01, v11, v10, xf, zf)
 	return v1*zf + v0*(1-zf)
 end
 
-local function heightmaps(minp, maxp)
+function mapgen_rivers.make_heightmaps(minp, maxp)
 
-	local polygons = make_polygons(minp, maxp)
+	local polygons = mapgen_rivers.make_polygons(minp, maxp)
 	local incr = maxp.z-minp.z+1
 
 	local terrain_height_map = {}
@@ -46,50 +82,57 @@ local function heightmaps(minp, maxp)
 				-- = 0: on riverbank
 				-- > 0: inside river
 				local depth_factors = {
-					r_west - xf,
-					r_north - zf,
-					xf - r_east,
-					zf - r_south,
-					c_NW-xf-zf,
-					xf-zf-c_NE,
-					xf+zf-c_SE,
-					zf-xf-c_SW,
+					r_west  -    xf , -- West edge (1)
+					r_north -    zf , -- North edge (2)
+					r_east  - (1-xf), -- East edge (3)
+					r_south - (1-zf), -- South edge (4)
+					c_NW -    xf  -    zf , -- North-West corner (5)
+					c_NE - (1-xf) -    zf , -- North-East corner (6)
+					c_SE - (1-xf) - (1-zf), -- South-East corner (7)
+					c_SW -    xf  - (1-zf), -- South-West corner (8)
 				}
 
-				-- Find the maximal depth factor and determine to which river it belongs
-				local depth_factor_max = 0
+				-- Find the maximal depth factor, which determines to which of the 8 river sections (4 edges + 4 corners) the current point belongs.
+				-- If imax is still at 0, it means that we are not in a river.
+				local dpmax = 0
 				local imax = 0
 				for i=1, 8 do
-					if depth_factors[i] >= depth_factor_max then
-						depth_factor_max = depth_factors[i]
+					if depth_factors[i] > dpmax then
+						dpmax = depth_factors[i]
 						imax = i
 					end
 				end
 
-				-- Transform the coordinates to have xf and zf = 0 or 1 in rivers (to avoid rivers having lateral slope and to accomodate the surrounding smoothly)
-				if imax == 0 then
-					local x0 = max(r_west, c_NW-zf, zf-c_SW)
-					local x1 = min(r_east, c_NE+zf, c_SE-zf)
-					local z0 = max(r_north, c_NW-xf, xf-c_NE)
-					local z1 = min(r_south, c_SW+xf, c_SE-xf)
-					xf = (xf-x0) / (x1-x0)
-					zf = (zf-z0) / (z1-z0)
-				elseif imax == 1 then
-					xf = 0
-				elseif imax == 2 then
-					zf = 0
-				elseif imax == 3 then
-					xf = 1
-				elseif imax == 4 then
-					zf = 1
-				elseif imax == 5 then
-					xf, zf = 0, 0
-				elseif imax == 6 then
-					xf, zf = 1, 0
-				elseif imax == 7 then
-					xf, zf = 1, 1
-				elseif imax == 8 then
-					xf, zf = 0, 1
+				-- Transform the coordinates to have xfc and zfc = 0 or 1 in rivers (to avoid rivers having lateral slope and to accomodate the riverbanks smoothly)
+				local xfc, zfc
+				-- xfc:
+				if imax == 0 or imax == 2 or imax == 4 then -- river segment does not constrain X coordinate, so accomodate xf in function of other river sections
+					local x0 =   max(r_west-dpmax, c_NW-zf-dpmax, c_SW-(1-zf)-dpmax, 0) -- new xf will be bounded to 0 by western riverbank
+					local x1 = 1-max(r_east-dpmax, c_NE-zf-dpmax, c_SE-(1-zf)-dpmax, 0) -- and bounded to 1 by eastern riverbank
+					if x0 >= x1 then
+						xfc = 0.5
+					else
+						xfc = (xf-x0) / (x1-x0)
+					end
+				elseif imax == 1 or imax == 5 or imax == 8 then -- river at the western side of the polygon
+					xfc = 0
+				else -- 3, 6, 7 : river at the eastern side of the polygon
+					xfc = 1
+				end
+
+				-- Same for zfc:
+				if imax == 0 or imax == 1 or imax == 3 then -- river segment does not constrain Z coordinate, so accomodate zf in function of other river sections
+					local z0 =   max(r_north-dpmax, c_NW-xf-dpmax, c_NE-(1-xf)-dpmax, 0) -- new zf will be bounded to 0 by northern riverbank
+					local z1 = 1-max(r_south-dpmax, c_SW-xf-dpmax, c_SE-(1-xf)-dpmax, 0) -- and bounded to 1 by southern riverbank
+					if z0 >= z1 then
+						zfc = 0.5
+					else
+						zfc = (zf-z0) / (z1-z0)
+					end
+				elseif imax == 2 or imax == 5 or imax == 6 then -- river at the northern side of the polygon
+					zfc = 0
+				else -- 4, 7, 8 : river at the southern side of the polygon
+					zfc = 1
 				end
 
 				-- Determine elevation by interpolation
@@ -99,12 +142,12 @@ local function heightmaps(minp, maxp)
 					vdem[2],
 					vdem[3],
 					vdem[4],
-					xf, zf
+					xfc, zfc
 				))
 
 				-- Spatial gradient of the interpolation
-				local slope_x = zf*(vdem[3]-vdem[4]) + (1-zf)*(vdem[2]-vdem[1]) < 0
-				local slope_z = xf*(vdem[3]-vdem[2]) + (1-xf)*(vdem[4]-vdem[1]) < 0
+				local slope_x = zfc*(vdem[3]-vdem[4]) + (1-zfc)*(vdem[2]-vdem[1]) < 0
+				local slope_z = xfc*(vdem[3]-vdem[2]) + (1-xfc)*(vdem[4]-vdem[1]) < 0
 				local lake_id = 0
 				if slope_x then
 					if slope_z then
@@ -121,15 +164,15 @@ local function heightmaps(minp, maxp)
 				end
 				local lake_height = max(floor(poly.lake[lake_id]), terrain_height)
 
-				if imax > 0 and depth_factor_max > 0 then
-					terrain_height = min(max(lake_height, sea_level) - floor(1+depth_factor_max*riverbed_slope), terrain_height)
+				if imax > 0 and dpmax > 0 then
+					terrain_height = min(max(lake_height, sea_level) - floor(1+dpmax*riverbed_slope), terrain_height)
 				end
 
 				terrain_height_map[i] = terrain_height
 				lake_height_map[i] = lake_height
 			else
-				terrain_height_map[i] = MAP_BOTTOM
-				lake_height_map[i] = MAP_BOTTOM
+				terrain_height_map[i] = out_elev
+				lake_height_map[i] = out_elev
 			end
 			i = i + 1
 		end
@@ -137,5 +180,3 @@ local function heightmaps(minp, maxp)
 
 	return terrain_height_map, lake_height_map
 end
-
-return heightmaps

init.lua

@@ -1,275 +1,16 @@
+-- Main file, calls the other files and triggers main functions
+
 mapgen_rivers = {}
 
 local modpath = minetest.get_modpath(minetest.get_current_modname()) .. '/'
 mapgen_rivers.modpath = modpath
 mapgen_rivers.world_data_path = minetest.get_worldpath() .. '/river_data/'
 
-if minetest.get_mapgen_setting("mg_name") ~= "singlenode" then
-	minetest.set_mapgen_setting("mg_name", "singlenode", true)
-	minetest.log("warning", "[mapgen_rivers] Mapgen set to singlenode")
-end
-
 dofile(modpath .. 'settings.lua')
+dofile(modpath .. 'gridmanager.lua')
+dofile(modpath .. 'polygons.lua')
+dofile(modpath .. 'heightmap.lua')
+dofile(modpath .. 'mapgen.lua')
+dofile(modpath .. 'spawn.lua')
 
-local sea_level = mapgen_rivers.settings.sea_level
-local elevation_chill = mapgen_rivers.settings.elevation_chill
-local use_distort = mapgen_rivers.settings.distort
-local use_biomes = mapgen_rivers.settings.biomes
-local use_biomegen_mod = use_biomes and minetest.global_exists('biomegen')
-use_biomes = use_biomes and not use_biomegen_mod
-
-if use_biomegen_mod then
-	biomegen.set_elevation_chill(elevation_chill)
-end
-dofile(modpath .. 'noises.lua')
-
-local heightmaps = dofile(modpath .. 'heightmap.lua')
-
--- Linear interpolation
-local function interp(v00, v01, v11, v10, xf, zf)
-	local v0 = v01*xf + v00*(1-xf)
-	local v1 = v11*xf + v10*(1-xf)
-	return v1*zf + v0*(1-zf)
-end
-
--- Localize for performance
-local floor, min = math.floor, math.min
-
-local data = {}
-
-local noise_x_obj, noise_z_obj, noise_distort_obj, noise_heat_obj, noise_heat_blend_obj
-local noise_x_map = {}
-local noise_z_map = {}
-local noise_distort_map = {}
-local noise_heat_map = {}
-local noise_heat_blend_map = {}
-local mapsize
-local init = false
-
-local sumtime = 0
-local sumtime2 = 0
-local ngen = 0
-
-local function generate(minp, maxp, seed)
-	minetest.log("info", ("[mapgen_rivers] Generating from %s to %s"):format(minetest.pos_to_string(minp), minetest.pos_to_string(maxp)))
-
-	local chulens = {
-		x = maxp.x-minp.x+1,
-		y = maxp.y-minp.y+1,
-		z = maxp.z-minp.z+1,
-	}
-
-	if not init then
-		mapsize = {
-			x = chulens.x,
-			y = chulens.y+1,
-			z = chulens.z,
-		}
-		if use_distort then
-			noise_x_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.distort_x, mapsize)
-			noise_z_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.distort_z, mapsize)
-			noise_distort_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.distort_amplitude, chulens)
-		end
-		if use_biomes then
-			noise_heat_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.heat, chulens)
-			noise_heat_blend_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.heat_blend, chulens)
-		end
-		init = true
-	end
-
-	local t0 = os.clock()
-	local minp2d = {x=minp.x, y=minp.z}
-	if use_distort then
-		noise_x_obj:get_3d_map_flat(minp, noise_x_map)
-		noise_z_obj:get_3d_map_flat(minp, noise_z_map)
-		noise_distort_obj:get_2d_map_flat(minp2d, noise_distort_map)
-	end
-	if use_biomes then
-		noise_heat_obj:get_2d_map_flat(minp2d, noise_heat_map)
-		noise_heat_blend_obj:get_2d_map_flat(minp2d, noise_heat_blend_map)
-	end
-
-	local terrain_map, lake_map, incr, i_origin
-
-	if use_distort then
-		local xmin, xmax, zmin, zmax = minp.x, maxp.x, minp.z, maxp.z
-		local i = 0
-		local i2d = 0
-		for z=minp.z, maxp.z do
-			for y=minp.y, maxp.y+1 do
-				for x=minp.x, maxp.x do
-					i = i+1
-					i2d = i2d+1
-					local distort = noise_distort_map[i2d]
-					local xv = noise_x_map[i]*distort + x
-					if xv < xmin then xmin = xv end
-					if xv > xmax then xmax = xv end
-					noise_x_map[i] = xv
-					local zv = noise_z_map[i]*distort + z
-					if zv < zmin then zmin = zv end
-					if zv > zmax then zmax = zv end
-					noise_z_map[i] = zv
-				end
-				i2d = i2d-chulens.x
-			end
-		end
-
-		local pminp = {x=floor(xmin), z=floor(zmin)}
-		local pmaxp = {x=floor(xmax)+1, z=floor(zmax)+1}
-		incr = pmaxp.x-pminp.x+1
-		i_origin = 1 - pminp.z*incr - pminp.x
-		terrain_map, lake_map = heightmaps(pminp, pmaxp)
-	else
-		terrain_map, lake_map = heightmaps(minp, maxp)
-	end
-
-	-- Check that there is at least one position that reaches min y
-	if minp.y > sea_level then
-		local y0 = minp.y
-		local is_empty = true
-		for i=1, #terrain_map do
-			if terrain_map[i] >= y0 or lake_map[i] >= y0 then
-				is_empty = false
-				break
-			end
-		end
-
-		-- If not, skip chunk
-		if is_empty then
-			local t = os.clock() - t0
-			ngen = ngen + 1
-			sumtime = sumtime + t
-			sumtime2 = sumtime2 + t*t
-
-			minetest.log("verbose", "[mapgen_rivers] Skipping empty chunk (fully above ground level)")
-			minetest.log("verbose", ("[mapgen_rivers] Done in %5.3f s"):format(t))
-			return
-		end
-	end
-
-	local c_stone = minetest.get_content_id("default:stone")
-	local c_dirt = minetest.get_content_id("default:dirt")
-	local c_lawn = minetest.get_content_id("default:dirt_with_grass")
-	local c_dirtsnow = minetest.get_content_id("default:dirt_with_snow")
-	local c_snow = minetest.get_content_id("default:snowblock")
-	local c_sand = minetest.get_content_id("default:sand")
-	local c_water = minetest.get_content_id("default:water_source")
-	local c_rwater = minetest.get_content_id("default:river_water_source")
-	local c_ice = minetest.get_content_id("default:ice")
-
-	local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
-	vm:get_data(data)
-
-	local a = VoxelArea:new({MinEdge = emin, MaxEdge = emax})
-	local ystride = a.ystride -- Tip : the ystride of a VoxelArea is the number to add to the array index to get the index of the position above. It's faster because it avoids to completely recalculate the index.
-
-	local nid = mapsize.x*(mapsize.y-1) + 1
-	local incrY = -mapsize.x
-	local incrX = 1 - mapsize.y*incrY
-	local incrZ = mapsize.x*mapsize.y - mapsize.x*incrX - mapsize.x*mapsize.y*incrY
-
-	local i2d = 1
-
-	for z = minp.z, maxp.z do
-		for x = minp.x, maxp.x do
-			local ivm = a:index(x, maxp.y+1, z)
-			local ground_above = false
-			local temperature
-			if use_biomes then
-				temperature = noise_heat_map[i2d]+noise_heat_blend_map[i2d]
-			end
-			local terrain, lake
-			if not use_distort then
-				terrain = terrain_map[i2d]
-				lake = lake_map[i2d]
-			end
-
-			for y = maxp.y+1, minp.y, -1 do
-				if use_distort then
-					local xn = noise_x_map[nid]
-					local zn = noise_z_map[nid]
-					local x0 = floor(xn)
-					local z0 = floor(zn)
-
-					local i0 = i_origin + z0*incr + x0
-					local i1 = i0+1
-					local i2 = i1+incr
-					local i3 = i2-1
-
-					terrain = interp(terrain_map[i0], terrain_map[i1], terrain_map[i2], terrain_map[i3], xn-x0, zn-z0)
-					lake = min(lake_map[i0], lake_map[i1], lake_map[i2], lake_map[i3])
-				end
-
-				if y <= maxp.y then
-
-					local is_lake = lake > terrain
-					if y <= terrain then
-						if not use_biomes or y <= terrain-1 or ground_above then
-							data[ivm] = c_stone
-						elseif is_lake or y < sea_level then
-							data[ivm] = c_sand
-						else
-							local temperature_y = temperature - y*elevation_chill
-							if temperature_y >= 15 then
-								data[ivm] = c_lawn
-							elseif temperature_y >= 0 then
-								data[ivm] = c_dirtsnow
-							else
-								data[ivm] = c_snow
-							end
-						end
-					elseif y <= lake and lake > sea_level then
-						if not use_biomes or temperature - y*elevation_chill >= 0 then
-							data[ivm] = c_rwater
-						else
-							data[ivm] = c_ice
-						end
-					elseif y <= sea_level then
-						data[ivm] = c_water
-					end
-				end
-
-				ground_above = y <= terrain
-
-				ivm = ivm - ystride
-				if use_distort then
-					nid = nid + incrY
-				end
-			end
-
-			if use_distort then
-				nid = nid + incrX
-			end
-			i2d = i2d + 1
-		end
-
-		if use_distort then
-			nid = nid + incrZ
-		end
-	end
-
-	if use_biomegen_mod then
-		biomegen.generate_all(data, a, vm, minp, maxp, seed)
-	else
-		vm:set_data(data)
-		minetest.generate_ores(vm, minp, maxp)
-	end
-
-	vm:set_lighting({day = 0, night = 0})
-	vm:calc_lighting()
-	vm:update_liquids()
-	vm:write_to_map()
-
-	local t = os.clock()-t0
-	ngen = ngen + 1
-	sumtime = sumtime + t
-	sumtime2 = sumtime2 + t*t
-	minetest.log("verbose", ("[mapgen_rivers] Done in %5.3f s"):format(t))
-end
-
-minetest.register_on_generated(generate)
-minetest.register_on_shutdown(function()
-	local avg = sumtime / ngen
-	local std = math.sqrt(sumtime2/ngen - avg*avg)
-	minetest.log("action", ("[mapgen_rivers] Mapgen statistics:\n- Mapgen calls: %4d\n- Mean time: %5.3f s\n- Standard deviation: %5.3f s"):format(ngen, avg, std))
-end)
+minetest.register_on_mods_loaded(mapgen_rivers.load_or_generate_grid)

load.lua

@@ -1,98 +0,0 @@
-local worldpath = mapgen_rivers.world_data_path
-
-local floor = math.floor
-local sbyte, schar = string.byte, string.char
-local unpk = unpack
-
-function mapgen_rivers.load_map(filename, bytes, signed, size, converter)
-	local file = io.open(worldpath .. filename, 'rb')
-	local data = file:read('*all')
-	if #data < bytes*size then
-		data = minetest.decompress(data)
-	end
-
-	local map = {}
-
-	for i=1, size do
-		local i0 = (i-1)*bytes+1
-		local elements = {data:byte(i0, i1)}
-		local n = sbyte(data, i0)
-		if signed and n >= 128 then
-			n = n - 256
-		end
-
-		for j=1, bytes-1 do
-			n = n*256 + sbyte(data, i0+j)
-		end
-
-		map[i] = n
-	end
-	file:close()
-
-	if converter then
-		for i=1, size do
-			map[i] = converter(map[i])
-		end
-	end
-
-	return map
-end
-
-local loader_mt = {
-	__index = function(loader, i)
-		local file = loader.file
-		local bytes = loader.bytes
-		file:seek('set', (i-1)*bytes)
-		local strnum = file:read(bytes)
-
-		local n = sbyte(strnum, 1)
-		if loader.signed and n >= 128 then
-			n = n - 256
-		end
-
-		for j=2, bytes do
-			n = n*256 + sbyte(strnum, j)
-		end
-
-		if loader.conv then
-			n = loader.conv(n)
-		end
-		loader[i] = n
-		return n
-	end,
-}
-
-function mapgen_rivers.interactive_loader(filename, bytes, signed, size, converter)
-	local file = io.open(worldpath .. filename, 'rb')
-	if file then
-		minetest.register_on_shutdown(function()
-			file:close()
-		end)
-		converter = converter or false
-		return setmetatable({file=file, bytes=bytes, signed=signed, size=size, conv=converter}, loader_mt)
-	end
-end
-
-function mapgen_rivers.write_map(filename, data, bytes)
-	local size = #data
-	local file = io.open(worldpath .. filename, 'wb')
-
-	local bytelist = {}
-	for j=1, bytes do
-		bytelist[j] = 0
-	end
-
-	for i=1, size do
-		local n = floor(data[i])
-		data[i] = n
-		for j=bytes, 2, -1 do
-			bytelist[j] = n % 256
-			n = floor(n / 256)
-		end
-		bytelist[1] = n % 256
-
-		file:write(schar(unpk(bytelist)))
-	end
-
-	file:close()
-end

mapgen.lua

@@ -0,0 +1,278 @@
+-- Mapgen loop and mapgen-related things
+
+if minetest.get_mapgen_setting("mg_name") ~= "singlenode" then
+	minetest.set_mapgen_setting("mg_name", "singlenode", true)
+	minetest.log("warning", "[mapgen_rivers] Mapgen set to singlenode")
+end
+
+local sea_level = mapgen_rivers.settings.sea_level
+local elevation_chill = mapgen_rivers.settings.elevation_chill
+local use_distort = mapgen_rivers.settings.distort
+local use_biomes = mapgen_rivers.settings.biomes
+local use_biomegen_mod = use_biomes and minetest.global_exists('biomegen')
+use_biomes = use_biomes and minetest.global_exists('default') and not use_biomegen_mod
+
+if use_biomegen_mod then
+	biomegen.set_elevation_chill(elevation_chill)
+end
+
+-- Linear interpolation
+local function interp(v00, v01, v11, v10, xf, zf)
+	local v0 = v01*xf + v00*(1-xf)
+	local v1 = v11*xf + v10*(1-xf)
+	return v1*zf + v0*(1-zf)
+end
+
+-- Localize for performance
+local floor, min = math.floor, math.min
+
+local data = {}
+
+local noise_x_obj, noise_z_obj, noise_distort_obj, noise_heat_obj, noise_heat_blend_obj
+local noise_x_map = {}
+local noise_z_map = {}
+local noise_distort_map = {}
+local noise_heat_map = {}
+local noise_heat_blend_map = {}
+local mapsize
+local init = false
+
+local sumtime = 0
+local sumtime2 = 0
+local ngen = 0
+
+function mapgen_rivers.make_chunk(minp, maxp, seed)
+	minetest.log("info", ("[mapgen_rivers] Generating from %s to %s"):format(minetest.pos_to_string(minp), minetest.pos_to_string(maxp)))
+
+	local chulens = {
+		x = maxp.x-minp.x+1,
+		y = maxp.y-minp.y+1,
+		z = maxp.z-minp.z+1,
+	}
+
+	if not init then
+		mapsize = {
+			x = chulens.x,
+			y = chulens.y+1,
+			z = chulens.z,
+		}
+		if use_distort then
+			noise_x_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.distort_x, mapsize)
+			noise_z_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.distort_z, mapsize)
+			noise_distort_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.distort_amplitude, chulens)
+		end
+		if use_biomes then
+			noise_heat_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.heat, chulens)
+			noise_heat_blend_obj = minetest.get_perlin_map(mapgen_rivers.noise_params.heat_blend, chulens)
+		end
+		init = true
+	end
+
+	local t0 = os.clock()
+	local minp2d = {x=minp.x, y=minp.z}
+	if use_distort then
+		noise_x_obj:get_3d_map_flat(minp, noise_x_map)
+		noise_z_obj:get_3d_map_flat(minp, noise_z_map)
+		noise_distort_obj:get_2d_map_flat(minp2d, noise_distort_map)
+	end
+	if use_biomes then
+		noise_heat_obj:get_2d_map_flat(minp2d, noise_heat_map)
+		noise_heat_blend_obj:get_2d_map_flat(minp2d, noise_heat_blend_map)
+	end
+
+	local terrain_map, lake_map, incr, i_origin
+
+	if use_distort then
+		local xmin, xmax, zmin, zmax = minp.x, maxp.x, minp.z, maxp.z
+		local i = 0
+		local i2d = 0
+		for z=minp.z, maxp.z do
+			for y=minp.y, maxp.y+1 do
+				for x=minp.x, maxp.x do
+					i = i+1
+					i2d = i2d+1
+					local distort = noise_distort_map[i2d]
+					local xv = noise_x_map[i]*distort + x
+					if xv < xmin then xmin = xv end
+					if xv > xmax then xmax = xv end
+					noise_x_map[i] = xv
+					local zv = noise_z_map[i]*distort + z
+					if zv < zmin then zmin = zv end
+					if zv > zmax then zmax = zv end
+					noise_z_map[i] = zv
+				end
+				i2d = i2d-chulens.x
+			end
+			i2d = i2d+chulens.x
+		end
+
+		local pminp = {x=floor(xmin), z=floor(zmin)}
+		local pmaxp = {x=floor(xmax)+1, z=floor(zmax)+1}
+		incr = pmaxp.x-pminp.x+1
+		i_origin = 1 - pminp.z*incr - pminp.x
+		terrain_map, lake_map = mapgen_rivers.make_heightmaps(pminp, pmaxp)
+	else
+		terrain_map, lake_map = mapgen_rivers.make_heightmaps(minp, maxp)
+	end
+
+	-- Check that there is at least one position that reaches min y
+	if minp.y > sea_level then
+		local y0 = minp.y
+		local is_empty = true
+		for i=1, #terrain_map do
+			if terrain_map[i] >= y0 or lake_map[i] >= y0 then
+				is_empty = false
+				break
+			end
+		end
+
+		-- If not, skip chunk
+		if is_empty then
+			if use_biomegen_mod and biomegen.skip_chunk then
+				biomegen.skip_chunk(minp, maxp)
+			end
+
+			local t = os.clock() - t0
+			ngen = ngen + 1
+			sumtime = sumtime + t
+			sumtime2 = sumtime2 + t*t
+
+			minetest.log("verbose", "[mapgen_rivers] Skipping empty chunk (fully above ground level)")
+			minetest.log("verbose", ("[mapgen_rivers] Done in %5.3f s"):format(t))
+			return
+		end
+	end
+
+	local c_stone = minetest.get_content_id("mapgen_stone")
+	local c_water = minetest.get_content_id("mapgen_water_source")
+	local c_rwater = minetest.get_content_id("mapgen_river_water_source")
+
+	local c_dirt, c_lawn, c_dirtsnow, c_snow, c_sand, c_ice
+	if use_biomes then
+		c_dirt = minetest.get_content_id("default:dirt")
+		c_lawn = minetest.get_content_id("default:dirt_with_grass")
+		c_dirtsnow = minetest.get_content_id("default:dirt_with_snow")
+		c_snow = minetest.get_content_id("default:snowblock")
+		c_sand = minetest.get_content_id("default:sand")
+		c_ice = minetest.get_content_id("default:ice")
+	end
+
+	local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
+	vm:get_data(data)
+
+	local a = VoxelArea:new({MinEdge = emin, MaxEdge = emax})
+	local ystride = a.ystride -- Tip : the ystride of a VoxelArea is the number to add to the array index to get the index of the position above. It's faster because it avoids to completely recalculate the index.
+
+	local nid = mapsize.x*(mapsize.y-1) + 1
+	local incrY = -mapsize.x
+	local incrX = 1 - mapsize.y*incrY
+	local incrZ = mapsize.x*mapsize.y - mapsize.x*incrX - mapsize.x*mapsize.y*incrY
+
+	local i2d = 1
+
+	for z = minp.z, maxp.z do
+		for x = minp.x, maxp.x do
+			local ivm = a:index(x, maxp.y+1, z)
+			local ground_above = false
+			local temperature
+			if use_biomes then
+				temperature = noise_heat_map[i2d]+noise_heat_blend_map[i2d]
+			end
+			local terrain, lake
+			if not use_distort then
+				terrain = terrain_map[i2d]
+				lake = lake_map[i2d]
+			end
+
+			for y = maxp.y+1, minp.y, -1 do
+				if use_distort then
+					local xn = noise_x_map[nid]
+					local zn = noise_z_map[nid]
+					local x0 = floor(xn)
+					local z0 = floor(zn)
+
+					local i0 = i_origin + z0*incr + x0
+					local i1 = i0+1
+					local i2 = i1+incr
+					local i3 = i2-1
+
+					terrain = interp(terrain_map[i0], terrain_map[i1], terrain_map[i2], terrain_map[i3], xn-x0, zn-z0)
+					lake = min(lake_map[i0], lake_map[i1], lake_map[i2], lake_map[i3])
+				end
+
+				if y <= maxp.y then
+
+					local is_lake = lake > terrain
+					if y <= terrain then
+						if not use_biomes or y <= terrain-1 or ground_above then
+							data[ivm] = c_stone
+						elseif is_lake or y < sea_level then
+							data[ivm] = c_sand
+						else
+							local temperature_y = temperature - y*elevation_chill
+							if temperature_y >= 15 then
+								data[ivm] = c_lawn
+							elseif temperature_y >= 0 then
+								data[ivm] = c_dirtsnow
+							else
+								data[ivm] = c_snow
+							end
+						end
+					elseif y <= lake and lake > sea_level then
+						if not use_biomes or temperature - y*elevation_chill >= 0 then
+							data[ivm] = c_rwater
+						else
+							data[ivm] = c_ice
+						end
+					elseif y <= sea_level then
+						data[ivm] = c_water
+					end
+				end
+
+				ground_above = y <= terrain
+
+				ivm = ivm - ystride
+				if use_distort then
+					nid = nid + incrY
+				end
+			end
+
+			if use_distort then
+				nid = nid + incrX
+			end
+			i2d = i2d + 1
+		end
+
+		if use_distort then
+			nid = nid + incrZ
+		end
+	end
+
+	if use_biomegen_mod then
+		biomegen.generate_all(data, a, vm, minp, maxp, seed)
+	else
+		vm:set_data(data)
+		minetest.generate_ores(vm, minp, maxp)
+	end
+
+	vm:set_lighting({day = 0, night = 0})
+	vm:calc_lighting()
+	vm:update_liquids()
+	vm:write_to_map()
+
+	local t = os.clock()-t0
+	ngen = ngen + 1
+	sumtime = sumtime + t
+	sumtime2 = sumtime2 + t*t
+	minetest.log("verbose", ("[mapgen_rivers] Done in %5.3f s"):format(t))
+end
+
+-- Enforce first position in mapgen callbacks
+table.insert(minetest.registered_on_generateds, 1, mapgen_rivers.make_chunk)
+--minetest.register_on_generated(mapgen_rivers.make_chunk)
+
+minetest.register_on_shutdown(function()
+	local avg = sumtime / ngen
+	local std = math.sqrt(sumtime2/ngen - avg*avg)
+	minetest.log("action", ("[mapgen_rivers] Mapgen statistics:\n- Mapgen calls: %4d\n- Mean time: %5.3f s\n- Standard deviation: %5.3f s"):format(ngen, avg, std))
+end)

mod.conf

@@ -1,4 +1,3 @@
 name = mapgen_rivers
 title = Map generator with realistic rivers
-depends = default
-optional_depends = biomegen
+optional_depends = biomegen, default

noises.lua

@@ -1,80 +0,0 @@
-local def_setting = mapgen_rivers.define_setting
-
-mapgen_rivers.noise_params = {
-	base = def_setting('np_base', 'noise', {
-		offset = 0,
-		scale = 300,
-		seed = 2469,
-		octaves = 8,
-		spread = {x=2048, y=2048, z=2048},
-		persist = 0.6,
-		lacunarity = 2,
-		flags = "eased",
-	}),
-
-	distort_x = def_setting('np_distort_x', 'noise', {
-		offset = 0,
-		scale = 1,
-		seed = -4574,
-		spread = {x=64, y=32, z=64},
-		octaves = 3,
-		persistence = 0.75,
-		lacunarity = 2,
-	}),
-
-	distort_z = def_setting('np_distort_z', 'noise', {
-		offset = 0,
-		scale = 1,
-		seed = -7940,
-		spread = {x=64, y=32, z=64},
-		octaves = 3,
-		persistence = 0.75,
-		lacunarity = 2,
-	}),
-
-	distort_amplitude = def_setting('np_distort_amplitude', 'noise', {
-		offset = 0,
-		scale = 10,
-		seed = 676,
-		spread = {x=1024, y=1024, z=1024},
-		octaves = 5,
-		persistence = 0.5,
-		lacunarity = 2,
-		flags = "absvalue",
-	}),
-
-	heat = minetest.get_mapgen_setting_noiseparams('mg_biome_np_heat'),
-	heat_blend = minetest.get_mapgen_setting_noiseparams('mg_biome_np_heat_blend'),
-}
-
--- Convert to number because Minetest API is not able to do it cleanly...
-for name, np in pairs(mapgen_rivers.noise_params) do
-	for field, value in pairs(np) do
-		if field ~= 'flags' and type(value) == 'string' then
-			np[field] = tonumber(value) or value
-		elseif field == 'spread' then
-			for dir, v in pairs(value) do
-				value[dir] = tonumber(v) or v
-			end
-		end
-	end
-end
-
-local heat = mapgen_rivers.noise_params.heat
-local base = mapgen_rivers.noise_params.base
-local settings = mapgen_rivers.settings
-heat.offset = heat.offset + settings.sea_level * settings.elevation_chill
-base.spread.x = base.spread.x / settings.blocksize
-base.spread.y = base.spread.y / settings.blocksize
-base.spread.z = base.spread.z / settings.blocksize
-
-for name, np in pairs(mapgen_rivers.noise_params) do
-	local lac = np.lacunarity or 2
-	if lac > 1 then
-		local omax = math.floor(math.log(math.min(np.spread.x, np.spread.y, np.spread.z)) / math.log(lac))+1
-		if np.octaves > omax then
-			minetest.log("warning", "[mapgen_rivers] Noise " .. name .. ": 'octaves' reduced to " .. omax)
-			np.octaves = omax
-		end
-	end
-end

polygons.lua

@@ -1,94 +1,23 @@
-local modpath = mapgen_rivers.modpath
-local mod_data_path = modpath .. 'river_data/'
-if not io.open(mod_data_path .. 'size', 'r') then
-	mod_data_path = modpath .. 'demo_data/'
-end
+-- Fetch polygons from a given areas, and compute their properties
+-- and find to which polygon every point belongs
 
-local world_data_path = mapgen_rivers.world_data_path
-minetest.mkdir(world_data_path)
-
-dofile(modpath .. 'load.lua')
-
-mapgen_rivers.grid = {}
-
-local X = mapgen_rivers.settings.grid_x_size
-local Z = mapgen_rivers.settings.grid_z_size
-
-local function offset_converter(o)
-	return (o + 0.5) * (1/256)
-end
-
-local load_all = mapgen_rivers.settings.load_all
-
--- Try to read file 'size'
-local sfile = io.open(world_data_path..'size', 'r')
-local first_mapgen = true
-if sfile then
-	X, Z = tonumber(sfile:read('*l')), tonumber(sfile:read('*l'))
-	sfile:close()
-	first_mapgen = false
-end
-
-if first_mapgen then
-	-- Generate a map!!
-	local pregenerate = dofile(mapgen_rivers.modpath .. '/pregenerate.lua')
-	minetest.register_on_mods_loaded(function()
-		minetest.log("action", '[mapgen_rivers] Generating grid, this may take a while...')
-		pregenerate(load_all)
-
-		if load_all then
-			local offset_x = mapgen_rivers.grid.offset_x
-			local offset_y = mapgen_rivers.grid.offset_y
-			for i=1, X*Z do
-				offset_x[i] = offset_converter(offset_x[i])
-				offset_y[i] = offset_converter(offset_y[i])
-			end
-		end
-	end)
-end
-
--- if data not already loaded
-if not (first_mapgen and load_all) then
-	local load_map
-	if load_all then
-		load_map = mapgen_rivers.load_map
-	else
-		load_map = mapgen_rivers.interactive_loader
-	end
-
-	minetest.register_on_mods_loaded(function()
-		if load_all then
-			minetest.log("action", '[mapgen_rivers] Loading full grid')
-		else
-			minetest.log("action", '[mapgen_rivers] Loading grid as interactive loaders')
-		end
-		local grid = mapgen_rivers.grid
-
-		grid.dem = load_map('dem', 2, true, X*Z)
-		grid.lakes = load_map('lakes', 2, true, X*Z)
-		grid.dirs = load_map('dirs', 1, false, X*Z)
-		grid.rivers = load_map('rivers', 4, false, X*Z)
-
-		grid.offset_x = load_map('offset_x', 1, true, X*Z, offset_converter)
-		grid.offset_y = load_map('offset_y', 1, true, X*Z, offset_converter)
-	end)
-end
-
-mapgen_rivers.grid.size = {x=X, y=Z}
+local blocksize = mapgen_rivers.settings.blocksize
+local X = math.floor(mapgen_rivers.settings.map_x_size / blocksize)
+local Z = math.floor(mapgen_rivers.settings.map_z_size / blocksize)
 
 local function index(x, z)
 	return z*X+x+1
 end
 
-local blocksize = mapgen_rivers.settings.blocksize
-local min_catchment = mapgen_rivers.settings.min_catchment
-local max_catchment = mapgen_rivers.settings.max_catchment
-
 local map_offset = {x=0, z=0}
-if mapgen_rivers.settings.center then
-	map_offset.x = blocksize*X/2
-	map_offset.z = blocksize*Z/2
-end
+mapgen_rivers.register_on_grid_loaded(function(grid)
+	X = grid.size.x
+	Z = grid.size.y
+	if mapgen_rivers.settings.center then
+		map_offset.x = blocksize*X/2
+		map_offset.z = blocksize*Z/2
+	end
+end)
 
 -- Localize for performance
 local floor, ceil, min, max, abs = math.floor, math.ceil, math.min, math.max, math.abs
@@ -119,7 +48,7 @@ local init = false
 
 -- On map generation, determine into which polygon every point (in 2D) will fall.
 -- Also store polygon-specific data
-local function make_polygons(minp, maxp)
+function mapgen_rivers.make_polygons(minp, maxp)
 
 	local grid = mapgen_rivers.grid
 	local dem = grid.dem
@@ -236,15 +165,15 @@ local function make_polygons(minp, maxp)
 				end
 			end
 
-			polygon.river_corners = {riverA, 1-riverB, 2-riverC, 1-riverD}
+			polygon.river_corners = {riverA, riverB, riverC, riverD}
 
 			-- Flow directions
 			local dirA, dirB, dirC, dirD = dirs[iA], dirs[iB], dirs[iC], dirs[iD]
 			-- Determine the river flux on the edges, by testing dirs values
 			local river_west = (dirA==1 and riverA or 0) + (dirD==3 and riverD or 0)
 			local river_north = (dirA==2 and riverA or 0) + (dirB==4 and riverB or 0)
-			local river_east = 1 - (dirB==1 and riverB or 0) - (dirC==3 and riverC or 0)
-			local river_south = 1 - (dirD==2 and riverD or 0) - (dirC==4 and riverC or 0)
+			local river_east = (dirB==1 and riverB or 0) + (dirC==3 and riverC or 0)
+			local river_south = (dirD==2 and riverD or 0) + (dirC==4 and riverC or 0)
 
 			polygon.rivers = {river_west, river_north, river_east, river_south}
 		end
@@ -252,5 +181,3 @@ local function make_polygons(minp, maxp)
 
 	return polygons
 end
-
-return make_polygons

pregenerate.lua

@@ -1,3 +1,8 @@
+-- Generate the grid using terrainlib_lua
+-- Only called on first mapgen, if there is no grid yet
+
+-- Constants
+
 local EvolutionModel = dofile(mapgen_rivers.modpath .. '/terrainlib_lua/erosion.lua')
 local twist = dofile(mapgen_rivers.modpath .. '/terrainlib_lua/twist.lua')
 
@@ -5,6 +10,7 @@ local blocksize = mapgen_rivers.settings.blocksize
 local tectonic_speed = mapgen_rivers.settings.tectonic_speed
 
 local np_base = table.copy(mapgen_rivers.noise_params.base)
+np_base.spread = vector.divide(np_base.spread, blocksize)
 
 local evol_params = mapgen_rivers.settings.evol_params
 
@@ -13,69 +19,132 @@ local time_step = mapgen_rivers.settings.evol_time_step
 local niter = math.ceil(time/time_step)
 time_step = time / niter
 
-local function pregenerate(keep_loaded)
-	local grid = mapgen_rivers.grid
-	local size = grid.size
+local use_margin = mapgen_rivers.settings.margin
+local margin_width = mapgen_rivers.settings.margin_width / blocksize
+local margin_elev = mapgen_rivers.settings.margin_elev
 
-	local seed = tonumber(minetest.get_mapgen_setting("seed"))
-	np_base.seed = (np_base.seed or 0) + seed
+local X = math.floor(mapgen_rivers.settings.map_x_size / blocksize)
+local Y = math.floor(mapgen_rivers.settings.map_z_size / blocksize)
 
-	local nobj_base = PerlinNoiseMap(np_base, {x=size.x, y=1, z=size.y})
-
-	local dem = nobj_base:get_3d_map_flat({x=0, y=0, z=0})
-	dem.X = size.x
-	dem.Y = size.y
-
-	local model = EvolutionModel(evol_params)
-	model.dem = dem
-	local ref_dem = model:define_isostasy(dem)
-
-	local tectonic_step = tectonic_speed * time_step
-	collectgarbage()
-	for i=1, niter do
-		minetest.log("info", "[mapgen_rivers] Iteration " .. i .. " of " .. niter)
-
-		model:diffuse(time_step)
-		model:flow()
-		model:erode(time_step)
-		if i < niter then
-			if tectonic_step ~= 0 then
-				nobj_base:get_3d_map_flat({x=0, y=tectonic_step*i, z=0}, ref_dem)
-			end
-			model:isostasy()
+local function margin(dem, width, elev)
+	local X, Y = dem.X, dem.Y
+	for i=1, width do
+		local c1 = ((i-1)/width) ^ 0.5
+		local c2 = (1-c1) * elev
+		local index = (i-1)*X + 1
+		for x=1, X do
+			dem[index] = dem[index] * c1 + c2
+			index = index + 1
+		end
+		index = i
+		for y=1, Y do
+			dem[index] = dem[index] * c1 + c2
+			index = index + X
+		end
+		index = X*(Y-i) + 1
+		for x=1, X do
+			dem[index] = dem[index] * c1 + c2
+			index = index + 1
+		end
+		index = X-i + 1
+		for y=1, Y do
+			dem[index] = dem[index] * c1 + c2
+			index = index + X
 		end
-
-		collectgarbage()
 	end
-	model:flow()
-
-	local mfloor = math.floor
-	local mmin, mmax = math.min, math.max
-	local offset_x, offset_y = twist(model.dirs, model.rivers, 5)
-	for i=1, size.x*size.y do
-		offset_x[i] = mmin(mmax(offset_x[i]*256, -128), 127)
-		offset_y[i] = mmin(mmax(offset_y[i]*256, -128), 127)
-	end
-
-	mapgen_rivers.write_map('dem', model.dem, 2)
-	mapgen_rivers.write_map('lakes', model.lakes, 2)
-	mapgen_rivers.write_map('dirs', model.dirs, 1)
-	mapgen_rivers.write_map('rivers', model.rivers, 4)
-	mapgen_rivers.write_map('offset_x', offset_x, 1)
-	mapgen_rivers.write_map('offset_y', offset_y, 1)
-	local sfile = io.open(mapgen_rivers.world_data_path .. 'size', "w")
-	sfile:write(size.x..'\n'..size.y)
-	sfile:close()
-
-	if keep_loaded then
-		grid.dem = model.dem
-		grid.lakes = model.lakes
-		grid.dirs = model.dirs
-		grid.rivers = model.rivers
-		grid.offset_x = offset_x
-		grid.offset_y = offset_y
-	end
-	collectgarbage()
 end
 
-return pregenerate
+-- Generate grid
+
+minetest.log("action", '[mapgen_rivers] Generating grid, this may take a while...')
+
+if X*Y > 4e6 then
+	minetest.log("warning", "[mapgen_rivers] You are going to generate a very large grid (>4M nodes). If you experience problems, you should increase blocksize or reduce map size.")
+end
+
+local seed = tonumber(minetest.get_mapgen_setting("seed"):sub(-10))
+np_base.seed = (np_base.seed or 0) + seed
+
+local nobj_base = PerlinNoiseMap(np_base, {x=X, y=1, z=Y})
+
+local dem = nobj_base:get_3d_map_flat({x=0, y=0, z=0})
+dem.X = X
+dem.Y = Y
+
+if use_margin then
+	margin(dem, margin_width, margin_elev)
+end
+
+local model = EvolutionModel(evol_params)
+model.dem = dem
+local ref_dem = model:define_isostasy(dem)
+
+local tectonic_step = tectonic_speed * time_step
+collectgarbage()
+for i=1, niter do
+	minetest.log("info", "[mapgen_rivers] Iteration " .. i .. " of " .. niter)
+
+	model:diffuse(time_step)
+	model:flow()
+	model:erode(time_step)
+	if i < niter then
+		if tectonic_step ~= 0 then
+			nobj_base:get_3d_map_flat({x=0, y=tectonic_step*i, z=0}, ref_dem)
+			if use_margin then
+				margin(ref_dem, margin_width, margin_elev)
+			end
+		end
+		model:isostasy()
+	end
+
+	collectgarbage()
+end
+model:flow()
+
+local mfloor = math.floor
+local mmin, mmax = math.min, math.max
+local unpk, schar = unpack, string.char
+local offset_x, offset_y = twist(model.dirs, model.rivers, 5)
+for i=1, X*Y do
+	offset_x[i] = mmin(mmax(offset_x[i]*256, -128), 127)
+	offset_y[i] = mmin(mmax(offset_y[i]*256, -128), 127)
+end
+
+-- Write data
+
+local datapath = mapgen_rivers.world_data_path
+minetest.mkdir(datapath)
+
+local sfile = io.open(datapath .. 'size', "w")
+sfile:write(X..'\n'..Y)
+sfile:close()
+
+local function write_file(filename, data, bytes)
+	local file = io.open(datapath .. filename, 'wb')
+
+	local bytelist = {}
+	for j=1, bytes do
+		bytelist[j] = 0
+	end
+
+	for i=1, #data do
+		local n = mfloor(data[i])
+		data[i] = n
+		for j=bytes, 2, -1 do
+			bytelist[j] = n % 256
+			n = mfloor(n / 256)
+		end
+		bytelist[1] = n % 256
+
+		file:write(schar(unpk(bytelist)))
+	end
+
+	file:close()
+end
+
+write_file('dem', model.dem, 2)
+write_file('lakes', model.lakes, 2)
+write_file('dirs', model.dirs, 1)
+write_file('rivers', model.rivers, 4)
+write_file('offset_x', offset_x, 1)
+write_file('offset_y', offset_y, 1)

settings.lua

@@ -1,7 +1,9 @@
+-- Read global and per-world settings
+
 local mtsettings = minetest.settings
 local mgrsettings = Settings(minetest.get_worldpath() .. '/mapgen_rivers.conf')
 
-mapgen_rivers.version = "1.0.2"
+mapgen_rivers.version = "1.0.2-dev1"
 
 local previous_version_mt = mtsettings:get("mapgen_rivers_version") or "0.0"
 local previous_version_mgr = mgrsettings:get("version") or "0.0"
@@ -19,13 +21,33 @@ end
 mtsettings:set("mapgen_rivers_version", mapgen_rivers.version)
 mgrsettings:set("version", mapgen_rivers.version)
 
+local defaults
+do
+	local f = io.open(mapgen_rivers.modpath .. "/settings_default.json")
+	defaults = minetest.parse_json(f:read("*all"))
+	f:close()
+end
+
+-- Convert strings to numbers in noise params because Minetest API is not able to do it cleanly...
+local function clean_np(np)
+	for field, value in pairs(np) do
+		if field ~= 'flags' and type(value) == 'string' then
+			np[field] = tonumber(value) or value
+		elseif field == 'spread' then
+			for dir, v in pairs(value) do
+				value[dir] = tonumber(v) or v
+			end
+		end
+	end
+end
+
 function mapgen_rivers.define_setting(name, dtype, default)
 	if dtype == "number" or dtype == "string" then
 		local v = mgrsettings:get(name)
 		if v == nil then
 			v = mtsettings:get('mapgen_rivers_' .. name)
 			if v == nil then
-				v = default
+				v = defaults[name]
 			end
 			mgrsettings:set(name, v)
 		end
@@ -39,7 +61,7 @@ function mapgen_rivers.define_setting(name, dtype, default)
 		if v == nil then
 			v = mtsettings:get_bool('mapgen_rivers_' .. name)
 			if v == nil then
-				v = default
+				v = defaults[name]
 			end
 			mgrsettings:set_bool(name, v)
 		end
@@ -49,10 +71,11 @@ function mapgen_rivers.define_setting(name, dtype, default)
 		if v == nil then
 			v = mtsettings:get_np_group('mapgen_rivers_' .. name)
 			if v == nil then
-				v = default
+				v = defaults[name]
 			end
 			mgrsettings:set_np_group(name, v)
 		end
+		clean_np(v)
 		return v
 	end
 end
@@ -60,33 +83,47 @@ end
 local def_setting = mapgen_rivers.define_setting
 
 mapgen_rivers.settings = {
-	center = def_setting('center', 'bool', true),
-	blocksize = def_setting('blocksize', 'number', 15),
+	center = def_setting('center', 'bool'),
+	blocksize = def_setting('blocksize', 'number'),
 	sea_level = tonumber(minetest.get_mapgen_setting('water_level')),
-	min_catchment = def_setting('min_catchment', 'number', 3600),
-	river_widening_power = def_setting('river_widening_power', 'number', 0.5),
-	riverbed_slope = def_setting('riverbed_slope', 'number', 0.4),
-	distort = def_setting('distort', 'bool', true),
-	biomes = def_setting('biomes', 'bool', true),
-	glaciers = def_setting('glaciers', 'bool', false),
-	glacier_factor = def_setting('glacier_factor', 'number', 8),
-	elevation_chill = def_setting('elevation_chill', 'number', 0.25),
+	min_catchment = def_setting('min_catchment', 'number'),
+	river_widening_power = def_setting('river_widening_power', 'number'),
+	riverbed_slope = def_setting('riverbed_slope', 'number'),
+	distort = def_setting('distort', 'bool'),
+	biomes = def_setting('biomes', 'bool'),
+	glaciers = def_setting('glaciers', 'bool'),
+	glacier_factor = def_setting('glacier_factor', 'number'),
+	elevation_chill = def_setting('elevation_chill', 'number'),
 
-	grid_x_size = def_setting('grid_x_size', 'number', 1000),
-	grid_z_size = def_setting('grid_z_size', 'number', 1000),
+	map_x_size = def_setting('map_x_size', 'number'),
+	map_z_size = def_setting('map_z_size', 'number'),
+	margin = def_setting('margin', 'bool'),
+	margin_width = def_setting('margin_width', 'number'),
+	margin_elev = def_setting('margin_elev', 'number'),
 	evol_params = {
-		K = def_setting('river_erosion_coef', 'number', 0.5),
-		m = def_setting('river_erosion_power', 'number', 0.4),
-		d = def_setting('diffusive_erosion', 'number', 0.5),
-		compensation_radius = def_setting('compensation_radius', 'number', 50),
+		K = def_setting('river_erosion_coef', 'number'),
+		m = def_setting('river_erosion_power', 'number'),
+		d = def_setting('diffusive_erosion', 'number'),
+		compensation_radius = def_setting('compensation_radius', 'number'),
 	},
-	tectonic_speed = def_setting('tectonic_speed', 'number', 70),
-	evol_time = def_setting('evol_time', 'number', 10),
-	evol_time_step = def_setting('evol_time_step', 'number', 1),
-
-	load_all = mtsettings:get_bool('mapgen_rivers_load_all')
+	tectonic_speed = def_setting('tectonic_speed', 'number'),
+	evol_time = def_setting('evol_time', 'number'),
+	evol_time_step = def_setting('evol_time_step', 'number'),
 }
 
+mapgen_rivers.noise_params = {
+	base = def_setting("np_base", "noise"),
+	distort_x = def_setting("np_distort_x", "noise"),
+	distort_z = def_setting("np_distort_z", "noise"),
+	distort_amplitude = def_setting("np_distort_amplitude", "noise"),
+
+	heat = minetest.get_mapgen_setting_noiseparams('mg_biome_np_heat'),
+	heat_blend = minetest.get_mapgen_setting_noiseparams('mg_biome_np_heat_blend'),
+}
+
+mapgen_rivers.noise_params.heat.offset = mapgen_rivers.noise_params.heat.offset +
+		mapgen_rivers.settings.sea_level * mapgen_rivers.settings.elevation_chill
+
 local function write_settings()
 	mgrsettings:write()
 end

settings_default.json

@@ -0,0 +1,70 @@
+{
+	"version": "1.0.2-dev1",
+
+	"center": true,
+	"water_level": 1,
+	"blocksize": 15,
+	"min_catchment": 3600,
+	"river_widening_power": 0.5,
+	"riverbed_slope": 0.4,
+	"distort": true,
+	"biomes": true,
+	"glaciers": false,
+	"glacier_factor": 8,
+	"elevation_chill": 0.25,
+
+	"map_x_size": 15000,
+	"map_z_size": 15000,
+	"margin": true,
+	"margin_width": 2000,
+	"margin_elev": -200,
+	"river_erosion_coef": 0.5,
+	"river_erosion_power": 0.4,
+	"diffusive_erosion": 0.5,
+	"compensation_radius": 50,
+	"tectonic_speed": 70,
+	"evol_time": 10,
+	"evol_time_step": 1,
+
+	"np_base": {
+		"offset": 0,
+		"scale": 300,
+		"seed": 2469,
+		"octaves": 8,
+		"spread": {"x": 2048, "y": 2048, "z": 2048},
+		"persist": 0.6,
+		"lacunarity": 2.0,
+		"flags": "eased"
+	},
+
+	"np_distort_x": {
+		"offset": 0,
+		"scale": 1,
+		"seed": -4574,
+		"octaves": 3,
+		"spread": {"x": 64, "y": 32, "z": 64},
+		"persist": 0.75,
+		"lacunarity": 2.0
+	},
+
+	"np_distort_z": {
+		"offset": 0,
+		"scale": 1,
+		"seed": -7940,
+		"octaves": 3,
+		"spread": {"x": 64, "y": 32, "z": 64},
+		"persist": 0.75,
+		"lacunarity": 2.0
+	},
+
+	"np_distort_amplitude": {
+		"offset": 0,
+		"scale": 10,
+		"seed": 676,
+		"octaves": 5,
+		"spread": {"x": 1024, "y": 1024, "z": 1024},
+		"persist": 0.5,
+		"lacunarity": 2.0,
+		"flags": "absvalue"
+	}
+}

settingtypes.txt

@@ -3,19 +3,35 @@
 #    Whether the map should be centered at x=0, z=0.
 mapgen_rivers_center (Center map) bool true
 
-#    Represents horizontal map scale. Every cell of the grid will be upscaled to
-#    a square of this size.
-#    For example if the grid size is 1000x1000 and block size is 12,
-#    the actual size of the map will be 12000.
+#    Every cell of the river grid will represent a square of this size.
+#    A lower value will result in more detailed terrain and finer computation
+#    of rivers, but will be slower to generate and use more resources.
+#
+#    WARNING: Excessively low values may cause crashes at pre-generation, due to
+#    memory issues
 mapgen_rivers_blocksize (Block size) float 15.0 2.0 100.0
 
-#    X size of the grid being generated
-#    Actual size of the map is grid_x_size * blocksize
-mapgen_rivers_grid_x_size (Grid X size) int 1000 50 5000
+#    X size of the map being generated
+#
+#    X size of the river grid will be this/blocksize
+#    When increasing, it is recommended to increase blocksize too
+mapgen_rivers_map_x_size (Map X size) int 15000 500 66000
 
-#    Z size of the grid being generated
-#    Actual size of the map is grid_z_size * blocksize
-mapgen_rivers_grid_z_size (Grid Z size) int 1000 50 5000
+#    Z size of the map being generated
+#
+#    Z size of the river grid will be this/blocksize
+#    When increasing, it is recommended to increase blocksize too
+mapgen_rivers_map_z_size (Map Z size) int 15000 500 66000
+
+#    If margin is enabled, elevation becomes closer to a fixed value when approaching
+#    the edges of the map.
+mapgen_rivers_margin (Margin) bool true
+
+#    Width of the transition at map borders, in nodes
+mapgen_rivers_margin_width (Margin width) float 2000.0 0.0 15000.0
+
+#    Elevation toward which to converge at map borders
+mapgen_rivers_margin_elev (Margin elevation) float -200.0 -31000.0 31000.0
 
 #    Minimal catchment area for a river to be drawn, in square nodes
 #    Lower value means bigger river density
@@ -54,11 +70,6 @@ mapgen_rivers_glacier_widening_factor (Glacier widening factor) float 8.0 1.0 20
 #    This results in mountains being more covered by snow.
 mapgen_rivers_elevation_chill (Elevation chill) float 0.25 0.0 5.0
 
-#    If enabled, loads all grid data in memory at init time.
-#    If disabled, data will be loaded on request and cached in memory.
-#    It's recommended to disable it for very large maps (> 2000 grid nodes or so)
-mapgen_rivers_load_all (Load all data in memory) bool false
-
 [Landscape evolution parameters]
 
 #    Modelled landscape evolution time, in arbitrary units

spawn.lua

@@ -0,0 +1,119 @@
+local np_distort_x = mapgen_rivers.noise_params.distort_x
+local np_distort_z = mapgen_rivers.noise_params.distort_z
+local np_distort_amplitude = mapgen_rivers.noise_params.distort_amplitude
+
+local nobj_distort_x, nobj_distort_z, nobj_distort_amplitude
+
+local sea_level = mapgen_rivers.settings.sea_level
+local distort = mapgen_rivers.settings.distort
+
+-- Linear interpolation
+local function interp(v00, v01, v11, v10, xf, zf)
+	local v0 = v01*xf + v00*(1-xf)
+	local v1 = v11*xf + v10*(1-xf)
+	return v1*zf + v0*(1-zf)
+end
+
+local function estimate_spawn_level(pos, use_distort)
+	local x, z = pos.x, pos.z
+	if distort and use_distort then
+		nobj_distort_x = nobj_distort_x or minetest.get_perlin(np_distort_x)
+		nobj_distort_z = nobj_distort_z or minetest.get_perlin(np_distort_z)
+		nobj_distort_amplitude = nobj_distort_amplitude or minetest.get_perlin(np_distort_amplitude)
+
+		local amplitude = nobj_distort_amplitude:get_2d({x=pos.x, y=pos.z})
+		x = x + nobj_distort_x:get_3d(pos)*amplitude
+		z = z + nobj_distort_z:get_3d(pos)*amplitude
+	end
+
+	local terrain, lakes = mapgen_rivers.make_heightmaps(
+		{x=math.floor(x),   z=math.floor(z)  },
+		{x=math.floor(x)+1, z=math.floor(z)+1}
+	)
+
+	local ex, ez = x % 1, z % 1
+	--local h = terrain[1]*(1-ex)*(1-ez) + terrain[2]*ex*(1-ez) + terrain[3]*(1-ex)*ez + terrain[4]*ex*ez
+	local h = interp(terrain[1], terrain[2], terrain[4], terrain[3], ex, ez)
+	local lake = math.min(lakes[1], lakes[2], lakes[3], lakes[4])
+
+	if h < lake or h <= sea_level then
+		return false, h
+	end
+
+	return true, h
+end
+
+local function get_spawn_level(x, z)
+	local pos = {x=x, z=z}
+	local suitable, y = estimate_spawn_level(pos, false)
+	if not suitable then
+		return
+	end
+
+	if not distort then
+		return math.floor(y) + 1
+	end
+
+	local low_bound = -math.huge
+	local high_bound = math.huge
+	local suitable_high = false
+
+	repeat
+		pos.y = math.max(math.min(math.floor(y+0.5), high_bound-1), low_bound+1)
+		suitable, y = estimate_spawn_level(pos, true)
+		if y > pos.y then
+			low_bound = pos.y
+		else
+			high_bound = pos.y
+			suitable_high = suitable
+		end
+	until high_bound - low_bound <= 1
+
+	if not suitable_high then
+		return
+	end
+
+	return high_bound + 1
+end
+minetest.get_spawn_level = get_spawn_level
+
+local rmax = 2000
+local function find_spawn_point(seed)
+	local level = get_spawn_level(0, 0)
+	if level then
+		return {x=0, y=level, z=0}
+	end
+
+	local pr = PcgRandom(seed or os.time())
+	local incr = 16
+	local r0 = 0
+
+	while r0 < rmax do
+		local r1 = r0 + incr
+		local r = pr:next(r0*r0+1, r1*r1) ^ 0.5
+		local a = pr:next() / 2147483648 * math.pi
+
+		local x = math.floor(math.cos(a) * r + 0.5)
+		local z = math.floor(math.sin(a) * r + 0.5)
+
+		level = get_spawn_level(x, z)
+		if level then
+			return {x=x, y=level, z=z}
+		end
+		r0 = r1
+	end
+end
+
+local function spawn_player(player)
+	if minetest.settings:get("static_spawnpoint") then
+		return
+	end
+
+	local spawn_point = find_spawn_point()
+	if spawn_point then
+		player:set_pos(spawn_point)
+	end
+end
+
+minetest.register_on_newplayer(spawn_player)
+minetest.register_on_respawnplayer(spawn_player)

terrainlib_lua/erosion.lua

@@ -134,7 +134,7 @@ local rivermapper = dofile(modpath .. "rivermapper.lua")
 local gaussian = dofile(modpath .. "gaussian.lua")
 
 local function flow(model)
-	model.dirs, model.lakes = rivermapper.flow_routing(model.dem, model.dirs, model.lakes, 'semirandom')
+	model.dirs, model.lakes = rivermapper.flow_routing(model.dem, model.dirs, model.lakes)
 	model.rivers = rivermapper.accumulate(model.dirs, model.rivers)
 end
 

terrainlib_lua/rivermapper.lua

@@ -10,50 +10,18 @@
 -- Big thanks to them for releasing this paper under a free license ! :)
 
 -- The algorithm here makes use of most of the paper's concepts, including the Planar Borůvka algorithm.
--- Only flow_local and accumulate_flow are custom algorithms.
 
 
-local function flow_local_semirandom(plist)
-	-- Determines how water should flow at 1 node scale.
-	-- The straightforward approach would be "Water will flow to the lowest of the 4 neighbours", but here water flows to one of the lower neighbours, chosen randomly, but probability depends on height difference.
-	-- This makes rivers better follow the curvature of the topography at large scale, and be less biased by pure N/E/S/W directions.
-	-- 'plist': array of downward height differences (0 if upward)
-	local sum = 0
-	for i=1, #plist do
-		sum = sum + plist[i] -- Sum of probabilities
-	end
-
-	if sum == 0 then
-		return 0
-	end
-	local r = math.random() * sum
-	for i=1, #plist do
-		local p = plist[i]
-		if r < p then
-			return i
-		end
-		r = r - p
-	end
-	return 0
-end
-
--- Maybe implement more flow methods in the future?
-local flow_methods = {
-	semirandom = flow_local_semirandom,
-}
-
 -- Applies all steps of the flow routing, to calculate flow direction for every node, and lake surface elevation.
 -- It's quite a hard piece of code, but we will go step by step and explain what's going on, so stay with me and... let's goooooooo!
-local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are optional tables to reuse for memory optimization, they may contain any data.
-	method = method or 'semirandom'
-	local flow_local = flow_methods[method] or flow_local_semirandom
-
+local function flow_routing(dem, dirs, lakes) -- 'dirs' and 'lakes' are optional tables to reuse for memory optimization, they may contain any data.
 	dirs = dirs or {}
 	lakes = lakes or {}
 
 	-- Localize for performance
 	local tremove = table.remove
 	local mmax = math.max
+	local mrand = math.random
 
 	local X, Y = dem.X, dem.Y
 	dirs.X = X
@@ -74,14 +42,29 @@ local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are
 	for y=1, Y do
 		for x=1, X do
 			local zi = dem[i]
-			local plist = { -- Get the height difference of the 4 neighbours (and 0 if uphill)
-				y<Y and mmax(zi-dem[i+X], 0) or 0, -- Southward
-				x<X and mmax(zi-dem[i+1], 0) or 0, -- Eastward
-				y>1 and mmax(zi-dem[i-X], 0) or 0, -- Northward
-				x>1 and mmax(zi-dem[i-1], 0) or 0, -- Westward
-			}
+			-- Determine how water should flow at 1 node scale.
+			-- The straightforward approach would be "Water will flow to the lowest of the 4 neighbours", but here water flows to one of the lower neighbours, chosen randomly, with probability depending on height difference.
+			-- This makes rivers better follow the curvature of the topography at large scale, and be less biased by pure N/E/S/W directions.
+			local pSouth = y<Y and mmax(zi-dem[i+X], 0) or 0
+			local pEast = x<X and mmax(zi-dem[i+1], 0) or 0
+			local pNorth = y>1 and mmax(zi-dem[i-X], 0) or 0
+			local pWest = x>1 and mmax(zi-dem[i-1], 0) or 0
+
+			local d = 0
+			local sum = pSouth + pEast + pNorth + pWest
+			local r = mrand() * sum
+			if sum > 0 then
+				if r < pSouth then
+					d = 1
+				elseif r-pSouth < pEast then
+					d = 2
+				elseif r-pSouth-pEast < pNorth then
+					d = 3
+				else
+					d = 4
+				end
+			end
 
-			local d = flow_local(plist)
 			-- 'dirs': Direction toward which water flow
 			-- 'dirs2': Directions from which water comes
 			dirs[i] = d
@@ -110,89 +93,172 @@ local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are
 	local links = {}
 	local basin_links
 
-	-- Function to analyse a link between two nodes
-	local function add_link(i1, i2, b1, isY)
-		-- i1, i2: coordinates of two nodes
-		-- b1: basin that contains i1
-		-- isY: whether the link is in Y direction
-		local b2
-		-- Note that basin number #0 represents the outside of the map; or if the coordinate is inside the map, means that the basin number is uninitialized.
-		if i2 == 0 then -- If outside the map
-			b2 = 0
-		else
-			b2 = basin_id[i2]
-			if b2 == 0 then -- If basin of i2 is not already computed, skip
-				return
-			end
-		end
-		if b2 ~= b1 then -- If these two nodes don't belong to the same basin, we have found a link between two adjacent basins
-			local elev = i2 == 0 and dem[i1] or mmax(dem[i1], dem[i2]) -- Elevation of the highest of the two sides of the link (or only i1 if b2 is map outside)
-			local l2 = basin_links[b2]
-			if not l2 then
-				l2 = {}
-				basin_links[b2] = l2
-			end
-			if not l2.elev or l2.elev > elev then -- If this link is lower than the lowest registered link between these two basins, register it as the new lowest pass
-				l2.elev = elev
-				l2.i = mmax(i1,i2)
-				l2.is_y = isY
-				l2[1] = b2
-				l2[2] = b1
-			end
-		end
-	end
-
 	for i=1, X*Y do
 		basin_id[i] = 0
 	end
 
-	for ib=1, nbasins do
-		-- Here we will recursively search upstream from the singular node to determine its drainage basin
-		local queue = {singular[ib]} -- Start with the singular node, then this queue will be filled with water donors neighbours
-		basin_links = {}
-		links[#links+1] = basin_links
-		while #queue > 0 do
-			local i = tremove(queue)
+	local cur = nbasins
+	local ib = 0
+	while cur > 0 do
+			local i = singular[cur]
+			cur = cur - 1
+			if dirs[i] == 0 then
+				basin_links = {}
+				links[#links+1] = basin_links
+				ib = ib + 1
+			end
 			basin_id[i] = ib
 			local d = dirs2[i] -- Get the directions water is coming from
 
 			-- Iterate through the 4 directions
+			-- Loop is unrolled on purpose, for performance (critical part!)
+			----------
+			-- EAST --
+			----------
 			if d >= 8 then -- River coming from the East
 				d = d - 8
-				queue[#queue+1] = i+1
+				cur = cur + 1
+				singular[cur] = i+1
 			-- If no river is coming from the East, we might be at the limit of two basins, thus we need to test adjacency.
 			elseif i%X > 0 then
-				add_link(i, i+1, ib, false)
+				if basin_id[i+1] ~= ib and basin_id[i+1] ~= 0 then
+					local b2 = basin_id[i+1]
+					local elev = mmax(dem[i], dem[i+1]) -- Elevation of the highest of the two sides of the link (or only i1 if b2 is map outside)
+					local l2 = basin_links[b2]
+					if not l2 then
+						l2 = {b2, ib, elev=elev, i=i+1, is_y=false}
+						basin_links[b2] = l2 -- Potential non-linear complexity here
+					elseif l2.elev > elev then -- If this link is lower than the lowest registered link between these two basins, register it as the new lowest pass
+						l2.elev = elev
+						l2.i = i+1
+						l2.is_y = false
+						l2[1] = b2
+						l2[2] = ib
+					end
+				end
 			else -- If the eastern neighbour is outside the map
-				add_link(i, 0, ib, false)
+				local l2 = basin_links[0]
+				if not l2 then
+					l2 = {0, ib, elev=dem[i], i=i, is_y=false}
+					basin_links[0] = l2
+				elseif l2.elev > dem[i] then
+					l2.elev = dem[i]
+					l2.i = i
+					l2.is_y = false
+					l2[1] = 0
+					l2[2] = ib
+				end
 			end
 
+			-----------
+			-- SOUTH --
+			-----------
 			if d >= 4 then -- River coming from the South
 				d = d - 4
-				queue[#queue+1] = i+X
+				cur = cur + 1
+				singular[cur] = i+X
 			elseif i <= X*(Y-1) then
-				add_link(i, i+X, ib, true)
+				if basin_id[i+X] ~= ib and basin_id[i+X] ~= 0 then
+					local b2 = basin_id[i+X]
+					local elev = mmax(dem[i], dem[i+X])
+					local l2 = basin_links[b2]
+					if not l2 then
+						l2 = {b2, ib, elev=elev, i=i+X, is_y=true}
+						basin_links[b2] = l2
+					elseif l2.elev > elev then
+						l2.elev = elev
+						l2.i = i+X
+						l2.is_y = true
+						l2[1] = b2
+						l2[2] = ib
+					end
+				end
 			else
-				add_link(i, 0, ib, true)
+				local l2 = basin_links[0]
+				if not l2 then
+					l2 = {0, ib, elev=dem[i], i=i, is_y=true}
+					basin_links[0] = l2
+				elseif l2.elev > dem[i] then
+					l2.elev = dem[i]
+					l2.i = i
+					l2.is_y = true
+					l2[1] = 0
+					l2[2] = ib
+				end
 			end
 
+			----------
+			-- WEST --
+			----------
 			if d >= 2 then -- River coming from the West
 				d = d - 2
-				queue[#queue+1] = i-1
+				cur = cur + 1
+				singular[cur] = i-1
 			elseif i%X ~= 1 then
-				add_link(i, i-1, ib, false)
+				if basin_id[i-1] ~= ib and basin_id[i-1] ~= 0 then
+					local b2 = basin_id[i-1]
+					local elev = mmax(dem[i], dem[i-1])
+					local l2 = basin_links[b2]
+					if not l2 then
+						l2 = {b2, ib, elev=elev, i=i, is_y=false}
+						basin_links[b2] = l2
+					elseif l2.elev > elev then
+						l2.elev = elev
+						l2.i = i
+						l2.is_y = false
+						l2[1] = b2
+						l2[2] = ib
+					end
+				end
 			else
-				add_link(i, 0, ib, false)
+				local l2 = basin_links[0]
+				if not l2 then
+					l2 = {0, ib, elev=dem[i], i=i, is_y=false}
+					basin_links[0] = l2
+				elseif l2.elev > dem[i] then
+					l2.elev = dem[i]
+					l2.i = i
+					l2.is_y = false
+					l2[1] = 0
+					l2[2] = ib
+				end
 			end
 
+			-----------
+			-- NORTH --
+			-----------
 			if d >= 1 then -- River coming from the North
-				queue[#queue+1] = i-X
+				cur = cur + 1
+				singular[cur] = i-X
 			elseif i > X then
-				add_link(i, i-X, ib, true)
+				if basin_id[i-X] ~= ib and basin_id[i-X] ~= 0 then
+					local b2 = basin_id[i-X]
+					local elev = mmax(dem[i], dem[i-X])
+					local l2 = basin_links[b2]
+					if not l2 then
+						l2 = {b2, ib, elev=elev, i=i, is_y=true}
+						basin_links[b2] = l2
+					elseif l2.elev > elev then
+						l2.elev = elev
+						l2.i = i
+						l2.is_y = true
+						l2[1] = b2
+						l2[2] = ib
+					end
+				end
 			else
-				add_link(i, 0, ib, true)
+				local l2 = basin_links[0]
+				if not l2 then
+					l2 = {0, ib, elev=dem[i], i=i, is_y=true}
+					basin_links[0] = l2
+				elseif l2.elev > dem[i] then
+					l2.elev = dem[i]
+					l2.i = i
+					l2.is_y = true
+					l2[1] = 0
+					l2[2] = ib
+				end
 			end
-		end
 	end
 	dirs2 = nil
 
@@ -223,26 +289,31 @@ local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are
 	-- Mareš' optimizations mainly consist in skipping elements that have over 8 links, until extra links are removed when other elements are merged.
 	-- Note that for this step we are only working on basins, not grid nodes.
 	local lowlevel = {}
-	for i, n in pairs(nlinks) do
-		if n <= 8 then
-			lowlevel[i] = links[i]
+	cur = 0
+	local ref = singular -- Reuse table
+	for i=0, nbasins do
+		if nlinks[i] <= 8 then
+			cur = cur + 1
+			lowlevel[cur] = i
+			ref[i] = cur
 		end
 	end
 
 	local basin_graph = {}
-	for n=1, nbasins do
+	for i=0, nbasins do
+		basin_graph[i] = {} -- Initialize (to ensure subtables don't go in the hash part)
+	end
+	for i=1, nbasins do
 		-- Iterate in lowlevel but its contents may change during the loop
-		-- 'next' called with only one argument always returns an element if table is not empty
-		local b1, lnk1 = next(lowlevel)
-		lowlevel[b1] = nil
+		local b1 = lowlevel[cur]
+		cur = cur - 1
+		local lnk1 = links[b1]
 
 		local b2
 		local lowest = math.huge
 		local lnk1 = links[b1]
-		local i = 0
 		-- Look for lowest link
 		for bn, bdata in pairs(lnk1) do
-			i = i + 1
 			if bdata.elev < lowest then
 				lowest = bdata.elev
 				b2 = bn
@@ -252,13 +323,7 @@ local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are
 		-- Add link to the graph, in both directions
 		local bound = lnk1[b2]
 		local bb1, bb2 = bound[1], bound[2]
-		if not basin_graph[bb1] then
-			basin_graph[bb1] = {}
-		end
-		if not basin_graph[bb2] then
-			basin_graph[bb2] = {}
-		end
-		basin_graph[bb1][bb2] = bound
+		basin_graph[bb1][bb2] = bound -- Potential non-linear complexity here
 		basin_graph[bb2][bb1] = bound
 
 		-- Merge basin b1 into b2
@@ -269,7 +334,9 @@ local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are
 		nlinks[b2] = nlinks[b2] - 1
 		-- When the number of links is changing, we need to check whether the basin can be added to / removed from 'lowlevel'
 		if nlinks[b2] == 8 then
-			lowlevel[b2] = lnk2
+			cur = cur + 1
+			lowlevel[cur] = b2
+			ref[b2] = cur
 		end
 		-- Look for basin 1's neighbours, and add them to basin 2 if they have a lower pass
 		for bn, bdata in pairs(lnk1) do
@@ -279,12 +346,16 @@ local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are
 			if lnkn[b2] then -- If bassin bn is also linked to b2
 				nlinks[bn] = nlinks[bn] - 1 -- Then bassin bn is losing a link because it keeps only one link toward b1/b2 after the merge
 				if nlinks[bn] == 8 then
-					lowlevel[bn] = lnkn
+					cur = cur + 1
+					lowlevel[cur] = bn
+					ref[bn] = cur
 				end
 			else -- If bn was linked to b1 but not to b2
 				nlinks[b2] = nlinks[b2] + 1 -- Then b2 is gaining a link to bn because of the merge
 				if nlinks[b2] == 9 then
-					lowlevel[b2] = nil
+					lowlevel[ref[b2]] = lowlevel[cur]
+					ref[lowlevel[cur]] = ref[b2]
+					cur = cur - 1
 				end
 			end
 
@@ -302,15 +373,17 @@ local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are
 	-- To orient the basin graph, we will consider that the ultimate basin water should flow into is the map outside (basin #0). We will start from it and recursively walk upstream to the neighbouring basins, using only links that are in the minimal spanning tree. This gives the flow direction of the links, and thus, the outlet of every basin.
 	-- This will also give lake elevation, which is the highest link encountered between map outside and the given basin on the spanning tree.
 	-- And within each basin, we need to modify flow directions to connect the singular node to the outlet.
-	local queue = {[0] = -math.huge}
+	local queue = {0}
+	local queuevalues = {-math.huge}
+	cur = 1
 	local basin_lake = {}
 	for n=1, nbasins do
 		basin_lake[n] = 0
 	end
 	local reverse = {3, 4, 1, 2, [0]=0}
-	for n=1, nbasins do
-		local b1, elev1 = next(queue) -- Pop from queue
-		queue[b1] = nil
+	while cur > 0 do
+		local b1, elev1 = queue[cur], queuevalues[cur] -- Pop from queue
+		cur = cur - 1
 		basin_lake[b1] = elev1
 		-- Iterate through b1's neighbours (according to the spanning tree)
 		for b2, bound in pairs(basin_graph[b1]) do
@@ -349,7 +422,9 @@ local function flow_routing(dem, dirs, lakes, method) -- 'dirs' and 'lakes' are
 			until dir == 0 -- Stop when reaching the singular node
 
 			-- Add basin b2 into the queue, and keep the highest link elevation, that will define the elevation of the lake in b2
-			queue[b2] = mmax(elev1, bound.elev)
+			cur = cur + 1
+			queue[cur] = b2
+			queuevalues[cur] = mmax(elev1, bound.elev)
 			-- Remove b1 from b2's neighbours to avoid coming back to b1
 			basin_graph[b2][b1] = nil
 		end
@@ -372,31 +447,25 @@ local function accumulate(dirs, waterq)
 	-- This means: how many nodes will give their water to that given node, directly or indirectly?
 	-- This is obtained by following rivers downstream and summing up the flow of every tributary, starting with a value of 1 at the sources.
 	-- This will give non-zero values for every node but only large values will be considered to be rivers.
-	waterq = waterq or {}
 	local X, Y = dirs.X, dirs.Y
+	waterq = waterq or {X=X, Y=Y}
 
 	local ndonors = {}
-	local waterq = {X=X, Y=Y}
 	for i=1, X*Y do
 		ndonors[i] = 0
 		waterq[i] = 1
 	end
 
 	-- Calculate the number of direct donors
-	for i1=1, X*Y do
-		local i2
-		local dir = dirs[i1]
-		if dir == 1 then
-			i2 = i1+X
-		elseif dir == 2 then
-			i2 = i1+1
-		elseif dir == 3 then
-			i2 = i1-X
-		elseif dir == 4 then
-			i2 = i1-1
-		end
-		if i2 then
-			ndonors[i2] = ndonors[i2] + 1
+	for i=1, X*Y do
+		if dirs[i] == 1 then
+			ndonors[i+X] = ndonors[i+X] + 1
+		elseif dirs[i] == 2 then
+			ndonors[i+1] = ndonors[i+1] + 1
+		elseif dirs[i] == 3 then
+			ndonors[i-X] = ndonors[i-X] + 1
+		elseif dirs[i] == 4 then
+			ndonors[i-1] = ndonors[i-1] + 1
 		end
 	end
 
@@ -438,5 +507,4 @@ end
 return {
 	flow_routing = flow_routing,
 	accumulate = accumulate,
-	flow_methods = flow_methods,
 }