mods that hopefully work for a TechAge-based pack

mods/techage_modpack/techage/basis/gravel_lib.lua

@@ -0,0 +1,118 @@
+--[[
+
+	TechAge
+	=======
+
+	Copyright (C) 2019 Joachim Stolberg
+
+	AGPL v3
+	See LICENSE.txt for more information
+
+	Gravel Sieve basis functions
+
+]]--
+
+-- Increase the probability over the natural occurrence
+local PROBABILITY_FACTOR = 2
+
+-- Ore probability table  (1/n)
+local ore_probability = {
+}
+
+local ProbabilityCorrections = {
+	["default:tin_lump"] = 0.3,  -- extensively used
+	["default:coal_lump"] = 0.2,  -- extensively used
+	["default:iron_lump"] = 0.5,  -- extensively used
+	["techage:baborium_lump"] = 99999,  -- mining required
+}
+
+local function wherein(item)
+	if type(item.wherein) == "table" then
+		for _,v in ipairs(item.wherein) do
+			if v == "default:stone" then
+				return true
+			end
+			if v == "everness:mineral_cave_stone" then
+				return true
+			end
+		end
+		return false
+	else
+		return item.wherein == "default:stone"
+	end
+end
+
+-- collect all registered ores and calculate the probability
+local function add_ores()
+	for _,item in  pairs(minetest.registered_ores) do
+		if not ore_probability[item.ore] and minetest.registered_nodes[item.ore] then
+			local drop = minetest.registered_nodes[item.ore].drop
+			if type(drop) == "string"
+			and drop ~= item.ore
+			and drop ~= ""
+			and item.ore_type == "scatter"
+			and wherein(item)
+			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 factor = 0.5
+				if item.y_max < -250 then
+					factor = -250 / item.y_max
+				end
+				local probability = (techage.ore_rarity / PROBABILITY_FACTOR) * item.clust_scarcity /
+						(item.clust_num_ores * factor)
+				-- lower value means higher probability
+				ore_probability[drop] = math.min(ore_probability[drop] or 100000, probability)
+			end
+		end
+	end
+	-- some corrections
+	for key, correction in pairs(ProbabilityCorrections) do
+		if ore_probability[key] then
+			ore_probability[key] = ore_probability[key] * correction
+			-- consider upper and lower level
+			ore_probability[key] = techage.in_range(ore_probability[key], 10, 100000)
+		end
+	end
+	local overall_probability = 0.0
+	for name,probability in pairs(ore_probability) do
+		minetest.log("info", string.format("[techage] %-32s %u", name, probability))
+		overall_probability = overall_probability + 1.0/probability
+	end
+	minetest.log("info", string.format("[techage] Overall probability %g", overall_probability))
+end
+
+minetest.register_on_mods_loaded(add_ores)
+
+--
+--  Change the probability of ores or register new ores for sieving
+--
+function techage.register_ore_for_gravelsieve(ore_name, probability)
+	ore_probability[ore_name] = probability
+end
+
+-- determine ore based on the calculated probability
+function techage.gravelsieve_get_random_gravel_ore()
+	for ore, probability in pairs(ore_probability) do
+		if math.random(probability) == 1 then
+			return ItemStack(ore)
+		end
+	end
+	if math.random(2) == 1 then
+		return ItemStack("default:gravel")
+	else
+		return ItemStack("techage:sieved_gravel")
+	end
+end
+
+function techage.gravelsieve_get_random_basalt_ore()
+	if math.random(techage.basalt_sieve_chance) == 1 then
+		return ItemStack("default:coal_lump")
+	elseif math.random(techage.basalt_sieve_chance) == 1 then
+		return ItemStack("default:iron_lump")
+	elseif math.random(2) == 1 then
+		return ItemStack("techage:basalt_gravel")
+	else
+		return ItemStack("techage:sieved_basalt_gravel")
+	end
+end