I've been working on homing arrows for ProjectE and I have the homing part working. However, after finding the entity to attack, the arrow doesn't change it's yaw or pitch and I have no clue about how to work this out. Does anybody know how I'd go about this? The class of code is below:

 

package moze_intel.projecte.gameObjs.entity;

import moze_intel.projecte.utils.WorldHelper;
import net.minecraft.entity.Entity;
import net.minecraft.entity.EntityLiving;
import net.minecraft.entity.EntityLivingBase;
import net.minecraft.entity.projectile.EntityArrow;
import net.minecraft.util.AxisAlignedBB;
import net.minecraft.world.World;

import java.util.List;

public class EntityHomingArrow extends EntityArrow
{
EntityLiving target;
World world;

private void init(World world)
{
	this.world = world;
}

public EntityHomingArrow(World world)
{
	super(world);
	init(world);
}

public EntityHomingArrow(World world, EntityLivingBase par2, float par3) 
{
	super(world, par2, par3);
	init(world);
}

@Override
public void onUpdate()
{
	//TODO Create proper custom arrow. This one is duplicating because of the super call for onUpdate();
	super.onUpdate();

	AxisAlignedBB box = this.boundingBox;

	if (target == null && !WorldHelper.isArrowInGround(this))
	{
		System.out.println("TARGET == NULL");
		AxisAlignedBB bBox = box.expand(8, 8, ;
		List<EntityLiving> list = this.worldObj.getEntitiesWithinAABB(EntityLiving.class, bBox);

		double distance = 100000;

		double disToEnt1 = 1000;

		for (EntityLiving entity : list)
		{
			double toIt = distanceTo(entity);

			double disToEnt2 = distanceTo(entity);

			if(disToEnt2 < disToEnt1){
				disToEnt1 = disToEnt2;
				target = entity;
			}

//				if (distance > toIt)
//				{
//					distance = toIt;
//					target = entity;
//				}
		}

		if (target == null)
		{
			return;
		}

		double xyz[] = checkDistance(target, this.posX, this.posY, this.posZ);

		double x = xyz[0];
		double y = xyz[1];
		double z = xyz[2];

		this.setThrowableHeading(x, y, z, 2.0F, 0.0F);
	}
	else if (!WorldHelper.isArrowInGround(this))
	{
		System.out.println("TARGET != NULL");
		if (target.getHealth() == 0) 
		{
			target = null;
			return;
		}

		world.spawnParticle("flame", box.maxX, box.maxY, box.maxZ, 0.0D, 0.0D, 0.0D);

		this.setPositionAndRotation(target.posX, target.posY, target.posZ, target.rotationYaw, target.rotationPitch);

		double xyz[] = checkDistance(target, this.posX, this.posY, this.posZ);

		double x = xyz[0];
		double y = xyz[1];
		double z = xyz[2];

		this.setThrowableHeading(x, y, z, 2.0F, 0.0F);
	}
}

private double distanceTo(EntityLiving entity)
{
	double [] ds = new double []
	{
		this.posX - entity.posX,
		this.posY - entity.posY,
		this.posZ - entity.posZ
	};

	double d = 0;

	for (int i = 0; i < 3; i++)
		d += ds[i] * ds[i];

	return Math.sqrt(d);
}

private double[] checkDistance(EntityLiving entity, double x, double y, double z){
	double rX, rY, rZ;

	System.out.println("LOCATION OF ENTITY: " + entity.posX + ", " + entity.posY + ", " + entity.posZ);

	rX = x;
	rY = y;
	rZ = z;

	if(entity.posX != x){
		if(entity.posX > x){
			rX =+ entity.posX;
		} else{
			rX--;
		}
	}

	if(entity.posY != y){
		if(entity.posY > y){
			rY =+ entity.posY;
		}
	}

	if(entity.posZ != z){
		if(entity.posZ > z){
			rZ =+ entity.posZ;
		} else{
			rZ--;
		}
	}

	double rValues[] = {rX, rY, rZ};

	for(int i = 0; i < rValues.length; i++){
		if(i == 0){System.out.println("x " + rValues[i]);}
		if(i == 1){System.out.println("y " + rValues[i]);}
		if(i == 2){System.out.println("z " + rValues[i]);}
	}

	return rValues;
}
}

Does the arrow still go toward the target it is homing?

 

If so then via basic trigonometry you can figure the pitch and yaw out. Sorry, I cant exactly post and example code as I am going to class but that is the basic thing to do.

Even if you had the correct code for targeting, your arrow would not work because you extend EntityArrow - the EntityArrow's onUpdate method and yours are conflicting.

 

A workaround is to override onUpdate and make sure to NOT call super.onUpdate; instead, call super.onEntityUpdate - this will bypass the EntityArrow update code (meaning you will need to duplicate it in your class, changing it where you need) and go straight to Entity#onUpdate, which you still need to be called.

 

For homing, the basic trig looks about like this:

double dx = target.posX - this.posX;
double dy = target.boundingBox.minY + (double)(target.height) - this.posY;
double dz = target.posZ - this.posZ;
setThrowableHeading(dx, dy, dz, 3.0F, 1.0F);

Of course, it can get more complicated if you want the arrow to have a pretty arc instead of aiming directly at the target every tick.