how to move an object, but make it stay on the ground

Question

im working on an enemy in my game that will shoot the player from a vertain distance, but move towards him and use melee attacks if it gets closer. everything for it is working so far except when my player jumps, the enemy follows it in the air. The line im using to make it follow the player is transform.Translate(Vector3.forward * moveSpeed * Time.deltaTime);

the problem is that im also making him rotate towards the players location so it can shoot from a distance

Quaternion rotation = Quaternion.LookRotation (target.position - transform.position); transform.rotation = Quaternion.Slerp(transform.rotation, rotation, Time.deltaTime * speed);

so how can i make him move toward the players location, but not be floating in the air to follow him when he jumps?

Answer 1

Hi

By default transform.Translate operates in local space, hence you being able to use 'vector3.forward' - i.e. move along your own forward (z) axis. That works fine until, as you say, your player jumps!

As you want to do something based on world space now ('up' from the point of view of the world) you'll need to start moving based on world space values. The simplest way I can see of writing this code in your game might be:

 //get our forward in world space
 Vector3 my_forward = transform.forward;
 
 //clear the y so we dont move up or down
 my_forward.y = 0;
 
 //normalize it, so we have a unit vector even after chopping out the y bit
 my_forward = my_forward.normalized;
 
 //scale it by the amount we want to move
 my_forward *= moveSpeed * Time.deltaTime;
 
 //and do our translation in world space 
 //(could be written transform.position += my_forward)
 transform.Translate(my_forward, Space.World);
 
 //or on much fewer lines!
 //Vector3 my_forward = transform.forward;
 //my_forward.y = 0;
 //transform.position += my_forward.normalized * moveSpeed * Time.deltaTime;

Lots of ways to write it that may vary depending on your situation, but that's the basic concept - get the direction you want to move, chop out the bits you don't want, renormalize it and then move by however much you want.

-Chris

how to move an object, but make it stay on the ground

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