[1.15.2] Find nearest structure locks

[Luminaire]

The following is a sample event handler.  One the following seed '45343', if you immediately walk towards the town in view from spawn, it will work for about 20 animals, and then always lock on one specific sheep, and all entities stop functioning forever.

 

Any idea how to accomplish below without jamming the server?

 

Thanks.

 

public class TestVillage {
    @SubscribeEvent
    public void checkSpawns(LivingSpawnEvent.CheckSpawn event) {

        Entity entity = event.getEntity();
        if (event.getWorld().isRemote()) {
            return;
        }
        if (!(entity instanceof LivingEntity)) {
            return;
        }

        if (entity instanceof AnimalEntity){
            BlockPos pos = entity.getPosition();
            ServerWorld entityWorld = (ServerWorld) entity.getEntityWorld();
            //The following will lock on one sheep after about 20 animals
            BlockPos block = entityWorld.findNearestStructure(Feature.VILLAGE.getStructureName(), pos, 70, false );
        }
    }
}
 

[ChampionAsh5357]

I'm confused on this statement. It doesn't lock onto one sheep, it finds the nearest village structure within 70 blocks of the specified position regardless of if the chunk exists or not. It will also only call whenever an animal is trying to be spawned in the world, so this seems a bit flawed for testing if a structure is present.

 

It doesn't lock necessarily, you'll just find the same structure within the specified distance unless you get far enough away for an animal to not be in range of a village. Not really deterministic.

[Luminaire]

My goal is to only allow certain animals to spawn when they are close to a village. That’s why I check each spawning entity to see if they are close to the village, and then deny any that aren’t close. 
 

The problem is for that sheep the findNearestStructure function just never returns, and all the entities just stop moving. I’m not sure why the function works fine for a bunch of animals, and then just never returns for one. 

[ChampionAsh5357]

1 hour ago, Luminaire said:

The problem is for that sheep the findNearestStructure function just never returns, and all the entities just stop moving.

Ok, can you show the entire code block for the event then? Because with what I see now, I think it might be a different place that is causing the infinite check. 

[Luminaire]

Here is the full code block for the event, that demonstrates all the functionality I am going for.  If you run this and walk into the nearby town, all the mobs will stop moving at that one sheep.

 

package com.luminairefarmanimals;

import net.minecraft.entity.Entity;
import net.minecraft.entity.LivingEntity;
import net.minecraft.entity.passive.AnimalEntity;
import net.minecraft.util.math.BlockPos;
import net.minecraft.world.gen.feature.Feature;
import net.minecraft.world.server.ServerWorld;
import net.minecraftforge.event.entity.living.LivingSpawnEvent;
import net.minecraftforge.eventbus.api.Event;
import net.minecraftforge.eventbus.api.SubscribeEvent;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import java.util.ArrayList;

public class TestVillage {
    private static final Logger LOGGER = LogManager.getLogger();

    @SubscribeEvent
    public void checkSpawns(LivingSpawnEvent.CheckSpawn event) {
        ArrayList<String> animals = new ArrayList<String>();
        animals.add("minecraft:pig");
        animals.add("minecraft:sheep");
        animals.add("minecraft:cow");
        animals.add("minecraft:chicken");
        Entity entity = event.getEntity();
        BlockPos pos = entity.getPosition();
        LOGGER.info("Entity Type:" + entity.getEntityString() + " - at: " + pos.getX() + ":" + pos.getZ()+ ":" + pos.getY());
        if (event.getWorld().isRemote()) {
            return;
        }
        if (!(entity instanceof LivingEntity)) {
            return;
        }

        if (entity instanceof AnimalEntity){
            ServerWorld entityWorld = (ServerWorld) entity.getEntityWorld();
            //The following will lock on one sheep after about 20 animals
            BlockPos block = entityWorld.findNearestStructure(Feature.VILLAGE.getStructureName(), pos, 70, false );
            if (block != null){
                if (!animals.contains(entity.getEntityString())){
                    event.setResult(Event.Result.DENY);
                }
            } else {
                if (animals.contains(entity.getEntityString())){
                    event.setResult(Event.Result.DENY);
                }
            }
        }
    }
}
 

[Draco18s]

46 minutes ago, Luminaire said:

        ArrayList<String> animals = new ArrayList<String>();
        animals.add("minecraft:pig");
        animals.add("minecraft:sheep");
        animals.add("minecraft:cow");
        animals.add("minecraft:chicken");

Don't recreate this array every time. Create it once.

 

47 minutes ago, Luminaire said:

        if (event.getWorld().isRemote()) {
            return;
        }
        if (!(entity instanceof LivingEntity)) {
            return;
        }

Use an || and do this as the first thing you do, so you don't create local unused variables for the garbage collector to clean up.

50 minutes ago, Luminaire said:

if (entity instanceof AnimalEntity){

Oh, you actually don't care about living entities, you care about AnimalEntities. Why the fuck didn't you use this as your early exit condition?

 

Not that either are related to your issue, but good coding practices should still be followed.

[Luminaire]

Once I have it actually working I will clean up the code.  I shoved everything into one class as well for this example, but I'll break it up into better pieces that can be reused if/when I add more features to the mod.

[Luminaire]

Any thoughts on how I can figure out why entityWorld.findNearestStructure never returns?

 

I'm really not sure what's going on.  Such a simple in theory mod to make animals only spawn near villages that is turning out to be really hard.

[Luminaire]

Looked more into this, and tried tracing the code.  It appears that the LivingSpawnEvent.CheckSpawn event cannot reliably get any information about the world around it, because during the time the chunk is loading if you attempt to do anything that affects the chunks (such as spawn a creature, or find a village) it will eventually lock up. The function ServerChunkProvider#getChunk uses multithreading and doesn't return.  This apparently was introduced as part of the 1.14 update, because before that you could do those things (such as how animania replaces animal spawns with it's own animals).

 

It appears that the entity spawning events became useless after 1.12 except for basic things.

 

I'm not sure what the replacement option is that can let me stop mob spawns, or replace mob spawns during generation based on the world, but I'm back to the drawing board.  Even if I could figure out in the CheckSpawn event when the chunks have loaded, most of the mobs the user would see would already be there.

I wonder what the minecraft developers would do here, and whether they came up with some alternate method.

[Beethoven92]

Have you considered looking into the jigsaw structure generation system? You know that when a village generates some entities are spawned with it...farm animals, cats, iron golem. I have personally never tried to mess with the jigsaw but probably there is a way to add new jigsaw pieces to the villages pool and making those pieces spawn entities.

[Luminaire]

My initial goal was to only allow farm animals (cows, chickens, pigs, sheep) near a village, and not allow them away from a village.  I wanted the wilds to feel wild, and farm animals to only be near villages where it makes sense.

This was supposed to go along with mods that add mobs so away from villages you'll find deer and wolves and bears, etc.

Unfortunately the most important part of this (stopping farm animals from spawning away from villages) can't use the new jigsaw pieces unless I don't understand their use.

[Beethoven92]

You just have to cancel the spawn of all farm animal entities, no matter where, handling the apposite event (or, perhaps, directly removing the animals from the every biome's spawn list?) . Then you would let your custom jigsaw pieces generate in villages, and have the farm animals generate with them.