Add initial environmental sounds mod with flowing water sounds

default:river_water_source can also create sound if desired as
rivers are considered to be flowing water.
A simple mod for now, with the intention to later use new engine
environmental sound features if/when they appear.

minetest.conf.example

@@ -64,3 +64,7 @@ default:torch 99,default:cobble 99
 # starting biome, is used.
 # Default value is false.
 #engine_spawn = false
+
+# Whether river water source nodes create flowing sounds.
+# Helps rivers create more sound, especially on level sections.
+#river_source_sounds = false

mods/env_sounds/README.txt

+Minetest Game mod: env_sounds
+=============================
+See license.txt for license information.
+
+Authors of source code
+----------------------
+paramat (MIT)
+
+Authors of media (sounds)
+-------------------------
+Yuval (CC0 1.0)
+https://freesound.org/people/Yuval/sounds/197023/
+  env_sounds_water.*.ogg

mods/env_sounds/init.lua

+-- Parameters
+
+local radius = 8 -- Water node search radius around player
+
+-- End of parameters
+
+
+local river_source_sounds = minetest.settings:get_bool("river_source_sounds")
+
+
+-- Update sound for player
+
+local function update_sound(player)
+	local player_name = player:get_player_name()
+	local ppos = player:get_pos()
+	local areamin = vector.subtract(ppos, radius)
+	local areamax = vector.add(ppos, radius)
+	local water_nodes = {"default:water_flowing", "default:river_water_flowing"}
+	if river_source_sounds then
+		table.insert(water_nodes, "default:river_water_source")
+	end
+	local wpos, _ = minetest.find_nodes_in_area(areamin, areamax, water_nodes)
+	local waters = #wpos
+	if waters == 0 then
+		return
+	end
+
+	-- Find average position of water positions
+	local wposav = vector.new()
+	for _, pos in ipairs(wpos) do
+		wposav.x = wposav.x + pos.x
+		wposav.y = wposav.y + pos.y
+		wposav.z = wposav.z + pos.z
+	end
+	wposav = vector.divide(wposav, waters)
+
+	minetest.sound_play(
+		"env_sounds_water",
+		{
+			pos = wposav,
+			to_player = player_name,
+			gain = math.min(0.04 + waters * 0.004, 0.4),
+		}
+	)
+end
+
+
+-- Update sound 'on joinplayer'
+
+minetest.register_on_joinplayer(function(player)
+	update_sound(player)
+end)
+
+
+-- Cyclic sound update
+
+local function cyclic_update()
+	for _, player in pairs(minetest.get_connected_players()) do
+		update_sound(player)
+	end
+	minetest.after(3.5, cyclic_update)
+end
+
+minetest.after(0, cyclic_update)

mods/env_sounds/license.txt

+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
+
+
+Licenses of media (sounds)
+--------------------------
+
+CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
+Yuval
+
+No Copyright
+
+The person who associated a work with this deed has dedicated the work to the
+public domain by waiving all of his or her rights to the work worldwide under
+copyright law, including all related and neighboring rights, to the extent
+allowed by law.
+
+You can copy, modify, distribute and perform the work, even for commercial
+purposes, all without asking permission. See Other Information below.
+
+Other Information:
+
+In no way are the patent or trademark rights of any person affected by CC0, nor
+are the rights that other persons may have in the work or in how the work is
+used, such as publicity or privacy rights.
+
+Unless expressly stated otherwise, the person who associated a work with this
+deed makes no warranties about the work, and disclaims liability for all uses
+of the work, to the fullest extent permitted by applicable law.
+
+When using or citing the work, you should not imply endorsement by the author
+or the affirmer.
+
+For more details:
+https://creativecommons.org/publicdomain/zero/1.0/

mods/env_sounds/mod.conf

+name = env_sounds
+description = Minetest Game mod: env_sounds
+depends = default

settingtypes.txt

@@ -64,3 +64,7 @@ enable_stairs_replace_abm (Replace old stairs) bool false
 #    If enabled, use the engine's spawn search which does not check for a
 #    suitable starting biome.
 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