gravelsieve distribution tweaks

gravelsieve/init.lua

@@ -44,7 +44,16 @@ gravelsieve = {
 
 dofile(minetest.get_modpath("gravelsieve") .. "/hammer.lua")
 
-gravelsieve.ore_rarity = tonumber(minetest.setting_get("gravelsieve_ore_rarity")) or 1
+local settings_get
+if minetest.setting_get then
+	settings_get = minetest.setting_get
+else
+	settings_get = function(...) endminetest.settings:get(...) end
+end
+gravelsieve.ore_rarity = tonumber(settings_get("gravelsieve_ore_rarity")) or 1.16
+gravelsieve.ore_max_elevation = tonumber(settings_get("gravelsieve_ore_max_elevation")) or 0
+gravelsieve.ore_min_elevation = tonumber(settings_get("gravelsieve_ore_min_elevation")) or -30912
+local y_spread = math.max(1 + gravelsieve.ore_max_elevation - gravelsieve.ore_min_elevation, 1)
 
 -- Increase the probability over the natural occurrence
 local PROBABILITY_FACTOR = 3
@@ -71,6 +80,17 @@ if minetest.get_modpath("pipeworks") and pipeworks ~= nil then
 	pipeworks_after_place = pipeworks.after_place
 end
 
+local function harmonic_sum(a, b)
+	return 1 / ((1 / a) + (1 / b))
+end
+
+local function calculate_probability(item)
+	local ymax = math.min(item.y_max, gravelsieve.ore_max_elevation)
+	local ymin = math.max(item.y_min, gravelsieve.ore_min_elevation)
+	return (gravelsieve.ore_rarity / PROBABILITY_FACTOR) *
+			item.clust_scarcity / (item.clust_num_ores * ((ymax - ymin) / y_spread))
+end
+
 -- collect all registered ores and calculate the probability
 local function add_ores()
 	for _,item in  pairs(minetest.registered_ores) do
@@ -84,24 +104,24 @@ local function add_ores()
 			and item.clust_scarcity ~= nil and item.clust_scarcity > 0
 			and item.clust_num_ores ~= nil and item.clust_num_ores > 0
 			and item.y_max ~= nil and item.y_min ~= nil then
-				local probability = (gravelsieve.ore_rarity / PROBABILITY_FACTOR) * item.clust_scarcity /
-						(item.clust_num_ores * ((item.y_max - item.y_min) / 65535))
-				if gravelsieve.ore_probability[drop] == nil then
-					gravelsieve.ore_probability[drop] = probability
-				else
-					-- harmonic sum
-					gravelsieve.ore_probability[drop] = 1.0 / ((1.0 / gravelsieve.ore_probability[drop]) +
-							(1.0 / probability))
+				local probability = calculate_probability(item)
+				if probability > 0 then
+					local cur_probability = gravelsieve.ore_probability[drop]
+					if cur_probability then
+						gravelsieve.ore_probability[drop] = harmonic_sum(cur_probability, probability)
+					else
+						gravelsieve.ore_probability[drop] = probability
+					end
 				end
 			end
 		end
 	end
 	local overall_probability = 0.0
 	for name,probability in pairs(gravelsieve.ore_probability) do
-		minetest.log("info", string.format("[gravelsieve] %-32s %u", name, probability))
+		minetest.log("info", ("[gravelsieve] %-32s %.02f"):format(name, probability))
 		overall_probability = overall_probability + 1.0/probability
 	end
-	minetest.log("info", string.format("[gravelsieve] Overall probability %g", overall_probability))
+	minetest.log("info", ("[gravelsieve] Overall probability %f"):format(overall_probability))
 end
 
 minetest.after(1, add_ores)

gravelsieve/mod.conf

@@ -1 +1,4 @@
 name=gravelsieve
+description=This mod includes a hammer to produce gravel from Cobblestone and a sieve to sift gravel to find ores.
+depends=default
+optional_depends=moreblocks,tubelib,hopper,pipeworks

gravelsieve/settingtypes.txt

@@ -2,4 +2,6 @@
 # 1.0 is according to the mapgen generator
 # 2.0 means half as many ores as result
 # 0.5 means twice as many ores as result
-gravelsieve_ore_rarity (Rarity factor to find ores) float 1.5
+gravelsieve_ore_rarity (Rarity factor to find ores) float 1.16
+gravelsieve_ore_max_elevation (Maximum elevation considered when calculating ore distribution) int 0 -30912 30927
+gravelsieve_ore_min_elevation (Minimum elevation considered when calculating ore distribution) int -30912 -30912 30927