Extended the API yet again, this time adding a Perlin-based temperature map

(two new variables defining min and max temperature, normalized to 0.53 = 0
degrees centigrade).

The values used for this new Perlin layer come from Splizard's Snow Biomes mod,
so other mods that use plantlife to create biomes should be able to blend
nicely with that mod.

plants_lib/init.lua

@@ -2,6 +2,10 @@
 -- 2013-01-00
 --
 -- License:  WTFPL
+--
+-- I got the temperature map idea from "hmmmm", values used for it came from
+--
+
 
 -- Various settings - most of these probably won't need to be changed
 
@@ -13,6 +17,11 @@ local perlin_octaves = 3
 local perlin_persistence = 0.6
 local perlin_scale = 100
 
+local temperature_seeddiff = 112
+local temperature_octaves = 3
+local temperature_persistence = 0.5
+local temperature_scale = 150
+
 local plantlife_limit = 0.1 -- compared against perlin noise.  lower = more abundant
 
 -- Local functions
@@ -35,7 +44,29 @@ end
 
 -- The spawning ABM
 
-spawn_on_surfaces = function(sdelay, splant, sradius, schance, ssurface, savoid, seed_diff, lightmin, lightmax, nneighbors, ocount, facedir, depthmax, altmin, altmax, sbiome, sbiomesize, sbiomecount, airsize, aircount)
+spawn_on_surfaces = function(
+						sdelay,
+						splant,
+						sradius,
+						schance,
+						ssurface,
+						savoid,
+						seed_diff,
+						lightmin,
+						lightmax,
+						nneighbors,
+						ocount,
+						facedir,
+						depthmax,
+						altmin,
+						altmax,
+						sbiome,
+						sbiomesize,
+						sbiomecount,
+						airsize,
+						aircount,
+						tempmin,
+						tempmax)
 	if seed_diff == nil then seed_diff = 0 end
 	if lightmin == nil then lightmin = 0 end
 	if lightmax == nil then lightmax = LIGHT_MAX end
@@ -49,6 +80,8 @@ spawn_on_surfaces = function(sdelay, splant, sradius, schance, ssurface, savoid,
 	if sbiomecount == nil then sbiomecount = 1 end
 	if airsize == nil then airsize = 0 end
 	if aircount == nil then aircount = 1 end
+	if tempmin == nil then tempmin = -2 end
+	if tempmax == nil then tempmax = 2 end
 	minetest.register_abm({
 		nodenames = { ssurface },
 		interval = sdelay,
@@ -57,9 +90,14 @@ spawn_on_surfaces = function(sdelay, splant, sradius, schance, ssurface, savoid,
 		action = function(pos, node, active_object_count, active_object_count_wider)
 			local p_top = { x = pos.x, y = pos.y + 1, z = pos.z }	
 			local n_top = minetest.env:get_node(p_top)
-			local perlin = minetest.env:get_perlin(seed_diff, perlin_octaves, perlin_persistence, perlin_scale )
-			local noise = perlin:get2d({x=p_top.x, y=p_top.z})
-			if noise > plantlife_limit and is_node_loaded(p_top) then
+			local perlin1 = minetest.env:get_perlin(seed_diff, perlin_octaves, perlin_persistence, perlin_scale)
+			local perlin2 = minetest.env:get_perlin(temperature_seeddiff, temperature_octaves, temperature_persistence, temperature_scale)
+			local noise1 = perlin1:get2d({x=p_top.x, y=p_top.z})
+			local noise2 = perlin2:get2d({x=p_top.x, y=p_top.z})
+			if noise1 > plantlife_limit 
+			  and noise2 >= tempmin
+			  and noise2 <= tempmax
+			  and is_node_loaded(p_top) then
 				local n_light = minetest.env:get_node_light(p_top, nil)
 				if minetest.env:find_node_near(p_top, sradius + math.random(-1.5,2), savoid) == nil
 				  and n_light >= lightmin
@@ -93,7 +131,20 @@ end
 
 -- The growing ABM
 
-grow_plants = function(gdelay, gchance, gplant, gresult, dry_early_node, grow_nodes, facedir, need_wall, grow_vertically, height_limit, ground_nodes, grow_function, seed_diff)
+grow_plants = function(
+					gdelay,
+					gchance,
+					gplant,
+					gresult,
+					dry_early_node,
+					grow_nodes,
+					facedir,
+					need_wall,
+					grow_vertically,
+					height_limit,
+					ground_nodes,
+					grow_function,
+					seed_diff)
 	if need_wall ~= true then need_wall = false end
 	if grow_vertically ~= true then grow_vertically = false end
 	if height_limit == nil then height_limit = 62000 end
@@ -144,10 +195,12 @@ grow_plants = function(gdelay, gchance, gplant, gresult, dry_early_node, grow_no
 				end
 			else
 				if seed_diff == nil then seed_diff = 0 end
-				local perlin = minetest.env:get_perlin(seed_diff, perlin_octaves, perlin_persistence, perlin_scale )
-				local noise = perlin:get2d({x=pos.x, y=pos.z})
-				dbg("Want to execute "..grow_function.."("..dump(pos)..","..noise..")")
-				assert(loadstring(grow_function.."("..dump(pos)..","..noise..")"))()
+				local perlin1 = minetest.env:get_perlin(seed_diff, perlin_octaves, perlin_persistence, perlin_scale)
+				local perlin2 = minetest.env:get_perlin(temperature_seeddiff, temperature_octaves, temperature_persistence, temperature_scale)
+				local noise1 = perlin1:get2d({x=p_top.x, y=p_top.z})
+				local noise2 = perlin2:get2d({x=p_top.x, y=p_top.z})
+				dbg("Call function: "..grow_function.."("..dump(pos)..","..noise1..","..noise2..")")
+				assert(loadstring(grow_function.."("..dump(pos)..","..noise1..","..noise2..")"))()
 			end
 		end
 	})