Process ABMs in a spherical volume instead of cubic

Increase active_block_range default to a 3 mapblock radius.

builtin/settingtypes.txt

@@ -758,7 +758,7 @@ active_object_send_range_blocks (Active object send range) int 3
 
 #    How large area of blocks are subject to the active block stuff, stated in mapblocks (16 nodes).
 #    In active blocks objects are loaded and ABMs run.
-active_block_range (Active block range) int 2
+active_block_range (Active block range) int 3
 
 #    From how far blocks are sent to clients, stated in mapblocks (16 nodes).
 max_block_send_distance (Max block send distance) int 10

minetest.conf.example

@@ -913,7 +913,7 @@
 #    How large area of blocks are subject to the active block stuff, stated in mapblocks (16 nodes).
 #    In active blocks objects are loaded and ABMs run.
 #    type: int
-# active_block_range = 2
+# active_block_range = 3
 
 #    From how far blocks are sent to clients, stated in mapblocks (16 nodes).
 #    type: int

src/defaultsettings.cpp

@@ -273,7 +273,7 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("profiler_print_interval", "0");
 	settings->setDefault("enable_mapgen_debug_info", "false");
 	settings->setDefault("active_object_send_range_blocks", "3");
-	settings->setDefault("active_block_range", "2");
+	settings->setDefault("active_block_range", "3");
 	//settings->setDefault("max_simultaneous_block_sends_per_client", "1");
 	// This causes frametime jitter on client side, or does it?
 	settings->setDefault("max_simultaneous_block_sends_per_client", "10");

src/environment.cpp

@@ -397,8 +397,11 @@ void fillRadiusBlock(v3s16 p0, s16 r, std::set<v3s16> &list)
 	for(p.Y=p0.Y-r; p.Y<=p0.Y+r; p.Y++)
 	for(p.Z=p0.Z-r; p.Z<=p0.Z+r; p.Z++)
 	{
-		// Set in list
-		list.insert(p);
+		// limit to a sphere
+		if (p.getDistanceFrom(p0) <= r) {
+			// Set in list
+			list.insert(p);
+		}
 	}
 }