Add API to weather mod

Co-authored-by: Till Affeldt <t.affeldt@tu-braunschweig.de>

game_api.txt

@@ -1169,3 +1169,21 @@ the log.
  * after logging the action, the original callback (if any) is called
  * `def`     See [Node definition]
  * `name`    Description of the node in the log message
+
+
+Weather API
+-----------
+
+The weather mod will constantly adjust weather effects seen by the player
+(that is: cloud parameters and shadow intensity).
+These can be influenced using this API.
+
+#### `weather.get = function(player)`
+
+* Returns the current weather effects seen by the player.
+  It returns a table with two keys:
+  * `clouds`:   A table (or `nil`) with cloud data following the same format as used for `player:set_clouds()`.
+  * `lighting`: A table (or `nil`) with lighting data following the same format as used for `player:set_lighting()`.
+* `player`: ObjectRef of the relevant player
+* You can override this function to change the weather effects by simply returning different values.
+  Setting `clouds` or `lighting` in the result table to `nil` will *prevent* those from changing.

mods/weather/api.lua

@@ -0,0 +1,32 @@
+local CYCLE = 8 -- Time period of cyclic clouds update in seconds
+
+weather = {}
+
+-- default implementation is empty
+function weather.get(player)
+	return {}
+end
+
+local function do_update()
+	for _, player in ipairs(minetest.get_connected_players()) do
+		local params = weather.get(player)
+		assert(params ~= nil, "weather.get() must not return nil")
+		if params.clouds then
+			player:set_clouds(params.clouds)
+		end
+		if params.lighting then
+			player:set_lighting(params.lighting)
+		end
+	end
+end
+
+local function cyclic_update()
+	do_update()
+	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)
+	do_update()
+end)

mods/weather/init.lua

@@ -1,10 +1,13 @@
+-- Always load the API
+dofile(minetest.get_modpath(minetest.get_current_modname()) .. "/api.lua")
+
 -- Disable by mapgen or setting
 
-local mg_name = minetest.get_mapgen_setting("mg_name")
 if minetest.settings:get_bool("enable_weather") == false then
 	return
 end
 
+local mg_name = minetest.get_mapgen_setting("mg_name")
 if mg_name == "v6" or mg_name == "singlenode" then
 	-- set a default shadow intensity for mgv6 and singlenode
 	minetest.register_on_joinplayer(function(player)
@@ -14,10 +17,9 @@ if mg_name == "v6" or mg_name == "singlenode" then
 	return
 end
 
--- Parameters
+-- Default implementation for noise based cloud appearance
 
 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,
@@ -59,19 +61,11 @@ local np_speedz = {
 	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
@@ -88,7 +82,7 @@ do
 	end
 end
 
-local function update_clouds()
+function weather.get(player)
 	-- Adjusted time in seconds
 	local time = math.floor(minetest.get_gametime() - t_offset)
 
@@ -102,42 +96,28 @@ local function update_clouds()
 	local n_speedx = nobj_speedx:get_2d({x = time, y = 0}) -- -1 to 1
 	local n_speedz = nobj_speedz:get_2d({x = time, y = 0}) -- -1 to 1
 
-	for _, player in ipairs(minetest.get_connected_players()) do
+	-- Fallback to mid-value 50 for very old worlds
-		-- Fallback to mid-value 50 for very old worlds
+	local humid = minetest.get_humidity(player:get_pos()) or 50
-		local humid = minetest.get_humidity(player:get_pos()) or 50
+	-- Default and classic density value is 0.4, make this happen
-		-- Default and classic density value is 0.4, make this happen
+	-- at humidity midvalue 50 when n_density is at midvalue 0.5.
-		-- at humidity midvalue 50 when n_density is at midvalue 0.5.
+	-- density_max = 0.25 at humid = 0.
-		-- density_max = 0.25 at humid = 0.
+	-- density_max = 0.8 at humid = 50.
-		-- density_max = 0.8 at humid = 50.
+	-- density_max = 1.35 at humid = 100.
-		-- density_max = 1.35 at humid = 100.
+	local density_max = 0.8 + ((humid - 50) / 50) * 0.55
-		local density_max = 0.8 + ((humid - 50) / 50) * 0.55
+	-- Range limit density_max to always have occasional
-		-- Range limit density_max to always have occasional
+	-- small scattered clouds at extreme low humidity.
-		-- small scattered clouds at extreme low humidity.
+	local density = rangelim(density_max, 0.2, 1.0) * n_density
-		local density = rangelim(density_max, 0.2, 1.0) * n_density
+
-		player:set_clouds({
+	return {
+		clouds = {
 			density = density,
 			thickness = math.max(math.floor(
 				rangelim(32 * humid / 100, 8, 32) * n_thickness
 				), 2),
 			speed = {x = n_speedx * 4, z = n_speedz * 4},
-		})
+		},
-		-- now adjust the shadow intensity
+		lighting = {
-		player:set_lighting({ shadows = { intensity = 0.7 * (1 - density) } })
+			shadows = { intensity = 0.7 * (1 - density) }
-	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)