What's the best way to move enemies around?

Unity Engine
1

I been working on a small tower defense style game and want to eventually have 100+ enemies moving about on my map at any given time and was wondering what the easiest way to manage their movement without dragging the game to a crawl.

so far I have tried rigid body, character controller and straight up translate:

Rigidbody method:

// code fragment dealing with enemy movment toward a target
        direction = mainTarget.transform.position - myTrans.position;
        targetRotation = Quaternion.LookRotation(direction, Vector3.up);
        myTrans.rotation = targetRotation;
        myTrans.rigidbody.velocity = direction.normalized * speed;

CharacterController:

        direction = mainTarget.transform.position - myTrans.position;
        targetRotation = Quaternion.LookRotation(direction, Vector3.up);
        myTrans.rotation = targetRotation;
        myController.SimpleMove(direction.normalized * speed );

These both work OK… probably since they are so similar, but the tend to lag up the system around 100 enemies in. With translate, my turrets fail to detect the enemies. Is there an easier way to move enemies around without using physics or an easier method for finding a direction / moving that has less impact on frame rate?

The character controller route lags a bit more then the rigid body route, but it also looks better since the enemies aren’t influenced by gravity (my rigid body enemies sometimes lay down on the job).

2

Why is that? Do they detect based on velocity?

3

I actually posted a solution to this earlier today.

http://forum.unity3d.com/threads/74963-Player-lt-gt-object-interaction

Basically you use a big trigger and maintain an array of transforms. You remove people from the list when they leave the trigger so it stays clean. (or when they die) They you can make decisions based off of distance, speed or whatever.