Applying constant Effects to Entities

This tutorial aims to show how to apply status effects to entities as long as these entities stand on the block. There are few issues that can encounter during trial-and-error, this guide is a workaround to these issues. List of potential problems is attached on the bottom of this page. Please visit Blocks 1.16.100+ first to have better understanding of components used in this tutorial.

Code #

We will need to add a couple things to our code, first let's start with property that will hold true and false values:

{
	"properties": {
		"wiki:is_on_block": [true, false]
	}
}

Now we need minecraft:ticking component that will check if our property is set to true and if so, trigger the event causing the effect to apply:

{
	"minecraft:ticking": {
		"range": [1, 1],
		"looping": true,
		"on_tick": {
			"event": "wiki:add_effect_event",
			"target": "self",
			"condition": "query.block_property('wiki:is_on_block`) == true"
		}
	}
}

We will use minecraft:on_step_on component to fire the event that will set our wiki:is_on_block to true:

{
	"minecraft:on_step_on": {
		"event": "wiki:change_property",
		"target": "self"
	}
}

Time to setup events section. First let's set the wiki:change_property event:

{
	"wiki:change_property": {
		"set_block_property": {
			"wiki:is_on_block": true
		}
	}
}

The last thing to add is event that will trigger the effect:

{
	"wiki:add_effect_event": {
		"run_command": {
			"command": ["effect @e[r=1] wither 2 2 false"]
		}
	}
}

And done! The code above will trigger the desired status effect as long as the entity is standing on a block.

Notes and issues #

Some context for the last part of the code:

• Q: Why does the status effect is triggered via run_command event function if there's already add_mob_effect event function that does that?

• A: add_mob_effect seems to not work if triggered from minecraft:ticking, that's why we use run_command as a workaround.

• Q: What is false value in wiki:is_on_block used for?

• A: false value is needed as setting wiki:is_on_block: true crashes the game. Setting wiki:is_on_block: [true] seems to work, however creates many debug log errors.

Depending on the desired outcome, there is a potential issue if effect duration is set to less than 2 seconds. If the effect is causing damage to an entity (for example via poison), that damage will be applied as soon as the effect is triggered. This results in the situation where entity receives damage faster than in vanilla Minecraft, since applying effect is quicker than damage that occurs from effects applied for more than 2 seconds (considering the entity is moving). To better understand this, simply set the effect duration in command to 1 second and compare the results. Having a 2 second duration allows the game to apply the damage in correct pace.

{
	"format_version": "1.16.100",
	"minecraft:block": {
		"description": {
			"identifier": "wiki:damage_block",
			"properties": {
				"wiki:is_on_block": [true, false]
			}
		},
		"components": {
			"minecraft:unit_cube": {},
			"minecraft:creative_category": {
					"category": "nature"
			},
			"minecraft:loot": "loot_tables/empty.json",
			"minecraft:on_step_on": {
				"event": "wiki:change_property",
				"target": "self"
			},
			"minecraft:ticking": {
				"range": [1, 1],
				"looping": true,
				"on_tick": {
					"event": "wiki:add_effect_event",
					"target": "self",
					"condition": "query.block_property('wiki:is_on_block') == true"
				}
			},
			"minecraft:breakonpush": true,
			"minecraft:destroy_time": 0.2,
			"minecraft:explosion_resistance": 1,
			"minecraft:friction": 0.6,
			"minecraft:flammable": {
				"flame_odds": 0,
				"burn_odds": 0
			},
			"minecraft:map_color": "#181818"
		},
		"events": {
			"wiki:change_property": {
				"set_block_property": {
					"wiki:is_on_block": true
				}
			},
			"wiki:add_effect_event": {
				"run_command": {
					"command": ["effect @e[r=1] wither 2 2 false"]
				}
			}
		}
	}
}