rewrite vacuum propagation

physics_propagation.lua

@@ -6,31 +6,40 @@ if has_monitoring then
   metric_space_vacuum_abm = monitoring.counter("vacuum_abm_count", "number of space vacuum abm calls")
 end
 
--- vacuum/air propagation
+-- vacuum propagation
 minetest.register_abm({
-  label = "space vacuum",
+  label = "air -> vacuum replacement",
 	nodenames = {"air"},
 	neighbors = {"vacuum:vacuum"},
 	interval = 1,
 	chance = 1,
 	action = vacuum.throttle(1000, function(pos)
-
+    -- update metrics
 		if metric_space_vacuum_abm ~= nil then metric_space_vacuum_abm.inc() end
 
-		if vacuum.no_vacuum_abm(pos) then
-			return
+		if vacuum.is_pos_in_space(pos) and not vacuum.near_powered_airpump(pos) then
+			-- in space, evacuate air
+			minetest.set_node(pos, {name = "vacuum:vacuum"})
 		end
+	end)
+})
+
+-- air propagation
+-- works slower than vacuum abm
+minetest.register_abm({
+  label = "vacuum -> air replacement",
+	nodenames = {"vacuum:vacuum"},
+	neighbors = {"air"},
+	interval = 1,
+	chance = 2,
+	action = vacuum.throttle(1000, function(pos)
+
+    -- update metrics
+		if metric_space_vacuum_abm ~= nil then metric_space_vacuum_abm.inc() end
 
 		if not vacuum.is_pos_in_space(pos) or vacuum.near_powered_airpump(pos) then
 			-- on earth or near a powered airpump
-			local node = minetest.find_node_near(pos, 1, {"vacuum:vacuum"})
-
-			if node ~= nil then
-				minetest.set_node(node, {name = "air"})
-			end
-		else
-			-- in space, evacuate air
-			minetest.set_node(pos, {name = "vacuum:vacuum"})
+			minetest.set_node(pos, {name = "air"})
 		end
 	end)
 })