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.

mods/env_sounds/init.lua

@@ -0,0 +1,64 @@
+-- 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)