61 lines
2.2 KiB
Markdown
61 lines
2.2 KiB
Markdown
---
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title: Active Block Modifiers
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layout: default
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root: ../../
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---
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## Introduction
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An active *A**ctive **B**lock **M**odifier (**ABM**) allows you to run code on
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certain nodes at specific intervals.
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Please be warned, ABMs which are too frequent or act on a large number of nodes
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cause massive amounts of lag. Use them sparingly.
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* Special Growing Grass
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* Your Turn
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## Special Growing Grass
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If you want to make a mod that adds a type of grass called alien grass
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- it grows near water on grassy blocks - you first register the grass, then
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write an ABM.
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{% highlight lua %}
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minetest.register_node("aliens:grass", {
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description = "Alien Grass",
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light_source = 3, -- The node radiates light. Values can be from 1 to 15
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tiles = {"aliens_grass.png"},
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groups = {choppy=1},
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on_use = minetest.item_eat(20)
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})
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minetest.register_abm({
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nodenames = {"default:dirt_with_grass"},
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neighbors = {"default:water_source", "default:water_flowing"},
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interval = 10.0, -- Run every 10 seconds
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chance = 50, -- Select every 1 in 50 nodes
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action = function(pos, node, active_object_count, active_object_count_wider)
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minetest.set_node({x = pos.x, y = pos.y + 1, z = pos.z}, {name = "aliens:grass"})
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end
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})
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{% endhighlight %}
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This ABM runs every ten seconds. There is a 1 in 5 chance of the ABM running on each
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node that has the correct name and the correct neighbors. If the ABM runs on a
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node, an alien grass node is placed above it. Please be warned, this will delete any
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node previously located in that position. To prevent this you should include a check
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using minetest.get_node to make sure there is space for the grass.
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Specifying a neighbor is optional. If you specify multiple neighbors, only one of them
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needs to be present to meet the requirements.
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Specifying chance is also optional. If you don't specify the chance, the ABM will
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always run when the other conditions are met.
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## Your Turn
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* **Midas touch**: Make water turn to gold blocks with a 1 in 100 chance, every 5 seconds.
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* **Decay**: Make wood turn into dirt when water is a neighbor.
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* **Burnin'**: Make every air node catch on fire. (Tip: "air" and "fire:basic_flame").
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Warning: expect the game to crash.
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