Any idea what affects the execution of ABMs?

[whoanders]

I've discovered minetest recently. To try out mod creation, I decided to create the project any good troll would make. I'm not going to explain it right away, this video should make the concept clear:

https://www.youtube.com/watch?v=qF_yTnX_s94

That's it: a self-replicating block. I made it by creating a block and applying the following ABM to it:

Code: Select all

minetest.register_abm({ nodenames = {"expanding_orb:orb"}, interval = 5, chance = 5,
			action = function(pos)
					for x = -1,1,1 do
						for y = 0,1,1 do
							for z = -1,1,1 do
								tempPos = vector.new(pos.x, pos.y, pos.z) -- Vector copy
								tempPos.x = tempPos.x + x
								tempPos.y = tempPos.y + y
								tempPos.z = tempPos.z + z
								minetest.add_node(tempPos, {name="expanding_orb:orb"})
							end
						end
					end
				 end
			})

As you can see by this piece of code, the block should multiply in all directions equally. However, as you can see in the video, blocks tend to appear way more in a certain direction. Where does this bias come from?

I haven't put this in the "problems" section as I don't really see this as a problem, but I'm curious about specifically why this happens.

[Desour]

Some of the newly added nodes are considered for abms in the current abm application. This is also why it grows so fast. The directional bias comes from the traversal order. See here: <https://github.com/minetest/minetest/bl ... t.cpp#L873>

P.S.: Make your variable local.

[whoanders]

That makes sense. Thanks for the explanation and source code link!

P.S.: Oops, you're right about the variable. I've not gotten fully used to this quirk of lua yet.