Add initial 'weather' mod to vary cloud density, thickness, velocity

mods/weather/README.txt

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+Minetest Game mod: weather
+==========================
+See license.txt for license information.
+Source code by paramat (MIT).

mods/weather/init.lua

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+-- Disable by mapgen or setting
+
+local mg_name = minetest.get_mapgen_setting("mg_name")
+if mg_name == "v6" or mg_name == "singlenode" or
+		minetest.settings:get_bool("enable_weather") == false then
+	return
+end
+
+
+-- Parameters
+
+local TSCALE = 600 -- Time scale of noise variation in seconds
+local CYCLE = 8 -- Time period of cyclic clouds update in seconds
+
+local np_density = {
+	offset = 0.5,
+	scale = 0.5,
+	spread = {x = TSCALE, y = TSCALE, z = TSCALE},
+	seed = 813,
+	octaves = 1,
+	persist = 0,
+	lacunarity = 2,
+}
+
+local np_thickness = {
+	offset = 0.5,
+	scale = 0.5,
+	spread = {x = TSCALE, y = TSCALE, z = TSCALE},
+	seed = 96,
+	octaves = 1,
+	persist = 0,
+	lacunarity = 2,
+}
+
+local np_speedx = {
+	offset = 0,
+	scale = 1,
+	spread = {x = TSCALE, y = TSCALE, z = TSCALE},
+	seed = 911923,
+	octaves = 1,
+	persist = 0,
+	lacunarity = 2,
+}
+
+local np_speedz = {
+	offset = 0,
+	scale = 1,
+	spread = {x = TSCALE, y = TSCALE, z = TSCALE},
+	seed = 5728,
+	octaves = 1,
+	persist = 0,
+	lacunarity = 2,
+}
+
+-- End parameters
+
+
+-- Initialise noise objects to nil
+
+local nobj_density = nil
+local nobj_thickness = nil
+local nobj_speedx = nil
+local nobj_speedz = nil
+
+
+-- Update clouds function
+
+local function rangelim(value, lower, upper)
+	return math.min(math.max(value, lower), upper)
+end
+
+local os_time_0 = os.time()
+local t_offset = math.random(0, 300000)
+
+local function update_clouds()
+	-- Time in seconds.
+	-- Add random time offset to avoid identical behaviour each server session.
+	local time = os.difftime(os.time(), os_time_0) - t_offset
+
+	nobj_density = nobj_density or minetest.get_perlin(np_density)
+	nobj_thickness = nobj_thickness or minetest.get_perlin(np_thickness)
+	nobj_speedx = nobj_speedx or minetest.get_perlin(np_speedx)
+	nobj_speedz = nobj_speedz or minetest.get_perlin(np_speedz)
+
+	local n_density = nobj_density:get2d({x = time, y = 0})
+	local n_thickness = nobj_thickness:get2d({x = time, y = 0})
+	local n_speedx = nobj_speedx:get2d({x = time, y = 0})
+	local n_speedz = nobj_speedz:get2d({x = time, y = 0})
+
+	for _, player in ipairs(minetest.get_connected_players()) do
+		local humid = minetest.get_humidity(player:get_pos())
+		player:set_clouds({
+			density = rangelim(humid / 100, 0.25, 1.0) * n_density,
+			thickness = math.max(math.floor(
+				rangelim(32 * humid / 100, 8, 32) * n_thickness
+				), 1),
+			speed = {x = n_speedx * 4, z = n_speedz * 4},
+		})
+	end
+end
+
+
+local function cyclic_update()
+	update_clouds()
+	minetest.after(CYCLE, cyclic_update)
+end
+
+
+minetest.after(0, cyclic_update)
+
+
+-- Update on player join to instantly alter clouds from the default
+
+minetest.register_on_joinplayer(function(player)
+	update_clouds()
+end)

mods/weather/license.txt

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+License of source code
+----------------------
+
+The MIT License (MIT)
+Copyright (C) 2019 paramat
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this
+software and associated documentation files (the "Software"), to deal in the Software
+without restriction, including without limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of the Software, and to permit
+persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
+For more details:
+https://opensource.org/licenses/MIT

mods/weather/mod.conf

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+name = weather
+description = Minetest Game mod: weather

settingtypes.txt

@@ -71,3 +71,7 @@ engine_spawn (Use engine spawn search) bool false
 #    Whether river water source nodes create flowing sounds.
 #    Helps rivers create more sound, especially on level sections.
 river_source_sounds (River source node sounds) bool false
+
+#    Enable cloud variation.
+#    Non-functional in V6 or Singlenode mapgens.
+enable_weather (Enable weather) bool true