So I'm trying to make an anti-Undead spell that deals direct damage to the Undead, but I'm having a problem actually dealing damage.

attackEntityFrom() seems to fail on the worldObj.isRemote check, indicating that the world is indeed, remote. When I put in a check for it, it fails it and attackEntityFrom() never gets called.

 

What can I do about this?

 

Code posted below.

@Override
public ItemStack onItemUseFinish(ItemStack itemStack, World world, EntityPlayer player)
{
	int mana = 0;
	ItemStack wand = FindWand(player);

	if(wand != null)
	{
		if(wand.getTagCompound() != null)
		{
			mana = wand.getTagCompound().getInteger("mana");
		}
		if(mana >= COST)
		{
			int distance = 64;

			//MovingObjectPosition position = Minecraft.getMinecraft().getRenderViewEntity().rayTrace(distance, 1.0f);
			Entity target = Minecraft.getMinecraft().objectMouseOver.entityHit; 

			if(target != null)
			{					
				if(target instanceof EntityLiving)
				{
					EntityLiving livingTarget = (EntityLiving)target;
					if(livingTarget.getCreatureAttribute() == EnumCreatureAttribute.UNDEAD)
					{
						ItemBaseWand castWand = (ItemBaseWand)wand.getItem();

						livingTarget.attackEntityFrom(DamageSource.inFire, DAMAGE);
						livingTarget.setFire(10);

						if(!world.isRemote)
						{	
							castWand.ModMana(wand, -COST);
						}
					}
				}
			}
		}
	}
	return itemStack;
}

You code has logical mistakes:

 

1st things 1st - why does "FindWand" starts with capital :C

 

Back to case:

Minecraft class is @SideOnly(Side.CLIENT) - therefore your item code will crash on dedicated.jar startup.

I am refering to this: Minecraft.getMinecraft().objectMouseOver.entityHit - this is for client-only usage and only via proxy code.

This is technical mistake. Based on this mistake you make next one:

You are using Client-sided code from server logical thread (!world.isRemote).

And calling data-changing methods from client logical side (data can be only manipulated on server thread) - I am talking about applying damage.

 

Some reading:

http://www.minecraftforge.net/forum/index.php/topic,33918.msg178740.html#msg178740

http://www.minecraftforge.net/forum/index.php/topic,22764.0.html

 

Now: In common code (Item's methods) you can perform proxy calls that can use Minecraft class - but that won't give you shit, because you don't need and can't do anything from client logical thread (only server can actually edit real data, client only displays it). What you need is to inside (!world.isRemote) call a method that will obtain target entity using server logical code.

 

To do that you could lookup e.g Arrow's code (for hitting targets) or you can almost literally copy client's method that does that, but do it on server thread.

You code has logical mistakes:

 

1st things 1st - why does "FindWand" starts with capital :C

It's just personal preference, and something drilled into me by my work. Variables start with lowercase, functions start with a capital.

 

Some reading:

http://www.minecraftforge.net/forum/index.php/topic,33918.msg178740.html#msg178740

http://www.minecraftforge.net/forum/index.php/topic,22764.0.html

Thanks! Very helpful.

 

Now: In common code (Item's methods) you can perform proxy calls that can use Minecraft class - but that won't give you shit, because you don't need and can't do anything from client logical thread (only server can actually edit real data, client only displays it). What you need is to inside (!world.isRemote) call a method that will obtain target entity using server logical code.

 

To do that you could lookup e.g Arrow's code (for hitting targets) or you can almost literally copy client's method that does that, but do it on server thread.

There's a problem there; using an axis aligned bounding box needs an Entity. I only have an Item. I'd need to create or get (I don't know from where) an Entity to use that. Could I use the player?

You code has logical mistakes:

 

1st things 1st - why does "FindWand" starts with capital :C

It's just personal preference, and something drilled into me by my work. Variables start with lowercase, functions start with a capital.

 

Really? For Java? That isn't really typical. Of course the compiler doesn't care and so the code will work fine, but whenever you share code (like how you're asking for help here, it hurts the other human's ability to quickly read your code).

Fixed it, finally. For those hoping to achieve similar results, try the following:

 

A simple function to find a target:

protected MovingObjectPosition FindTarget(EntityPlayer player, World world)
{		
Vec3 playerPosition = new Vec3(player.posX, player.posY + player.getEyeHeight(), player.posZ);
Vec3 normalisedLook = player.getLookVec().normalize();

Vec3 targetPosition = new Vec3(playerPosition.xCoord + (normalisedLook.xCoord * DISTANCE),
		playerPosition.yCoord + player.eyeHeight + (normalisedLook.yCoord * DISTANCE), 
		playerPosition.zCoord + (normalisedLook.zCoord * DISTANCE));

MovingObjectPosition position = world.rayTraceBlocks(playerPosition, targetPosition, true, true, false);

return position;
}

 

If you want to find all entities within an area, simply use the World.getEntitiesWithinAABBExcludingEntity(player, box) (I used player as I had no other entity available), where 'box' is a bounding box assembled from the data you get from your FindTarget call.

 

Hope this helps!