XNA create differences in enemies

Question

I created an enemy class for my game. It works well, except for one dilemma. When I spawn more than one enemy, eventually they begin to "overlap" and look like one enemy. I was wondering if anyone had any ideas on how to create more differences and spontaneity between the enemies. All help would be greatly appreciated.

Here is the class:

using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
using Microsoft.Xna.Framework.Net;
using Microsoft.Xna.Framework.Storage;

namespace Defender
{
public class Enemy
{


    Vector2 Location;
    public static Texture2D texture;


    float rotation;
    Rectangle rectangle;
    int shootTimer = 50;





    public void Draw(SpriteBatch spriteBatch)
    {
        rectangle = new Rectangle((int)Location.X, (int)Location.Y, 32, 32);
        spriteBatch.Draw(texture, Location, null, Color.White, rotation, new Vector2(16, 16), 1, SpriteEffects.None, 0);

    }



    public void Update(GameTime gameTime)
    {
        Rotate();
        Shoot();
        Move(gameTime);



    }

    public void Move(GameTime gameTime)
    {
        if (Vector2.Distance(Location, Game.player.Location) > 75)
        {

                Location.X += findDirection(Game.player.Location).X * (float)(gameTime.ElapsedGameTime.TotalMilliseconds / 20);
                Location.Y += findDirection(Game.player.Location).Y * (float)(gameTime.ElapsedGameTime.TotalMilliseconds / 20);

        }

    }


    private void Rotate()
    {



            float XDistance = Location.X - Game.player.Location.X;
            float YDistance = Location.Y - Game.player.Location.Y;


            rotation = (float)Math.Atan2(YDistance, XDistance);


    }

    private Vector2 findDirection(Vector2 target)
    {

            Vector2 direction = target - Location;
            direction.Normalize();
            return direction;

    }

    public void Shoot()
    {
        if (shootTimer > 0)
        {
            shootTimer--;
        }
        if (shootTimer == 0)
        {

            //find slope


            //create bullet
            Bullet bullet = new Bullet(Location, findDirection(new Vector2(Game.player.Location.X, Game.player.Location.Y)));
            Game.bulletList.Add(bullet);

            //reset timer 
            shootTimer = 50;


        }

    }



    public Enemy(Vector2 loc)
    {

        Location = loc;
    }


}

}

Answer 1

There are a couple of things you can do to fix this.

First off, you can try implementing collision on enemies so that they don't walk through one another. Depending on the enemy type you're fighting, it may or may not make sense for them to easily pass through one another (flying bugs, ghosts, and small creatures might make sense, but who knows how those T-rexes are all running in the same spot).

Alternately, you can try and add some random factor to the pathing algorithm your enemies are using. A couple of people talked about this in more detail on this page: Making the AI take different paths to each other

Answer 2

Have a look at Steering Behaviors.

There are many different kinds of behaviors that could help your enemies navigate more realistically, but one behavior that relates to what you are looking for is a "Separation" type of behavior (often used in Flocking behaviors (or boids)). This behavior states that all entities under this "rule" try to keep a small distance between each other. Using this rule, your enemies wouldn't overlap, and you wouldn't need to check for collisions either.

Some pseudo-code can be found here as well as a bit more in-depth explanation of how it works and can be implemented.

Answer 3

Well, you can use random number generator to create a little differences between enemy characteristics (speed, initial position, etc.)