Realm limits with exponential blend

README.txt

@@ -1,4 +1,4 @@
-subterrain 0.1.0 by paramat
+subterrain 0.1.1 by paramat
 For Minetest 0.4.8 stable
 Depends default
 Licenses: code WTFPL

init.lua

@@ -1,13 +1,14 @@
--- subterrain 0.1.0 by paramat
+-- subterrain 0.1.1 by paramat
 -- For Minetest 0.4.8 stable
 -- Depends default
 -- License: code WTFPL
 
 -- Parameters
 
-local YMAX = -113
-local TCAVE = 0.6 -- Cave threshold.
-		-- 1 = small rare caves, 0 = 1/2 ground volume, 0.5 = 1/3rd ground volume 
+local YMIN = -33000 -- Cave realm limits
+local YMAX = -256
+local TCAVE = 0.6 -- Cave threshold. 1 = small rare caves, 0.5 = 1/3rd ground volume, 0 = 1/2 ground volume
+local BLEND = 128 -- Cave blend distance near YMIN, YMAX
 
 -- 3D noise for caves
 
@@ -24,10 +25,13 @@ local np_cave = {
 
 subterrain = {}
 
+local yblmin = YMIN + BLEND * 1.5
+local yblmax = YMAX - BLEND * 1.5
+
 -- On generated function
 
 minetest.register_on_generated(function(minp, maxp, seed)
-	if maxp.y > YMAX then
+	if minp.y > YMAX or maxp.y < YMIN then
 		return
 	end
 
@@ -56,9 +60,17 @@ minetest.register_on_generated(function(minp, maxp, seed)
 	local nixyz = 1
 	for z = z0, z1 do -- for each xy plane progressing northwards
 		for y = y0, y1 do -- for each x row progressing upwards
+			local tcave
+			if y < yblmin then
+				tcave = TCAVE + ((yblmin - y) / BLEND) ^ 2
+			elseif y > yblmax then
+				tcave = TCAVE + ((y - yblmax) / BLEND) ^ 2
+			else
+				tcave = TCAVE
+			end
 			local vi = area:index(x0, y, z)
 			for x = x0, x1 do -- for each node do
-				if nvals_cave[nixyz] > 0.6 then
+				if nvals_cave[nixyz] > tcave then
 					data[vi] = c_air
 				end
 				nixyz = nixyz + 1
@@ -71,6 +83,7 @@ minetest.register_on_generated(function(minp, maxp, seed)
 	vm:set_lighting({day=0, night=0})
 	vm:calc_lighting()
 	vm:write_to_map(data)
+
 	local chugent = math.ceil((os.clock() - t1) * 1000)
 	print ("[subterrain] "..chugent.." ms")
 end)