I have been working on a new halo mod and wanted to know how to make an item shoot out a beam to attack entities

Look into entities, items, the vanilla bow and arrow, and check the forge wiki for a gun tutorial (I think I remember seeing one).

If you mean a continuous beam you have problems.

 

Well, only problem here would be handling dealing effect and rendering.

 

Make item have look at rightclicking and use methods. (I've never used this one but looks promising: onUsingTick())

In your ItemStack you will have to store ammo (power) that would decrement with rightclick/using.

Then you will need to use some GL and math (vectors and shit) to make a beam with limited range (that's just visual effect, client-side)

And ofc. to apply your actual effect you will need to use raytracing (have look at MovingObjectPosition.class, server-side)

Problem could be making limited range - don't make it too far, most of code for getting player's eyes direction are in vanilla so that should save time (you know, cross-hair?)

 

If you would have any actual code that would be nice.

i will see if i can get this to work with your suggestions.

 

ok as it seems i do not understand this at all, but i did make an outline for the item

package com.licky.items;

import com.licky.llb.StringLibrary;
import com.licky.mobs.CustomArrow;
import com.licky.mobs.EntityGrenade;
import com.licky.mobs.FuelRodBolt;

import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.enchantment.Enchantment;
import net.minecraft.enchantment.EnchantmentHelper;
import net.minecraft.entity.Entity;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.entity.projectile.EntitySnowball;
import net.minecraft.init.Items;
import net.minecraft.item.EnumAction;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.world.World;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.event.entity.player.ArrowLooseEvent;
import net.minecraftforge.event.entity.player.ArrowNockEvent;
import cpw.mods.fml.relauncher.Side;
import cpw.mods.fml.relauncher.SideOnly;

public class SentinelBeam extends Item{

private static final String __OBFID = "CL_00001777";

public SentinelBeam() {
	this.maxStackSize = 1;
	this.setMaxDamage(384);
}

public int getMaxItemUseDuration(ItemStack p_77626_1_) {
	return 72000;
}


public EnumAction getItemUseAction(ItemStack p_77661_1_) {
	return EnumAction.bow;
}
public ItemStack onUsingTick(ItemStack ItemI, World Seven,
	EntityPlayer Me){

return ItemI;

}

public ItemStack onItemRightClick(ItemStack p_77659_1_, World Seven,
		EntityPlayer Me) {

	if (Me.capabilities.isCreativeMode) {

	}
	//if (Me.inventory.hasItem(Items.redstone)) {


	//	this.getMaxItemUseDuration(p_77659_1_);
	//	}


	return p_77659_1_;
}


}