moving object on x axis without affecting z axis

Question

I have an NPC object in my 2d sidescrolling game. While he is far away from the player, I want him to patrol nearby area, by changing it's x coordinate in a range, but while x coordinate is changing, z coordinate is changing too. Here is the code:

 #pragma strict
 var range : float;
 private var start_x : float;
 
 
 
 function Start () {
     start_x = transform.position.x;
     range = gameObject.GetComponent(NPC_set_attributes).npc_patrolling_range;
 }
 
 function Update () {
 
     transform.Translate(Vector3(gameObject.GetComponent(NPC_set_attributes).npc_move_speed*Time.deltaTime, 0.0, 0.0), Space.Self);
     
     if(transform.position.x >= start_x + range){
         Change_direction();
     } else if(transform.position.x <= start_x-range) {
         Change_direction();
     }
 }
 
 function Change_direction () {
     gameObject.GetComponent(NPC_set_attributes).npc_move_speed = -gameObject.GetComponent(NPC_set_attributes).npc_move_speed;
     gameObject.GetComponent(NPC_set_attributes).npc_facing_left = !gameObject.GetComponent(NPC_set_attributes).npc_facing_left;
 }

Don't know what to do. "Freeze Position Z" won't help, because I need to be able to move my object on z axis too.

Answer 1

Space.Self in Translate makes the object move in its local directions - if the object has any rotation, it will move in other axes too. Try Space.World instead: this will Translate only in the X axis with this code. By the way, you could improve performance and write a lot less if the script reference was cached in a variable at Start:

 #pragma strict

 var range : float;
 private var start_x : float;
 private var attribs: NPC_set_attributes; // reference to the NPC_set_attributes script
 
 function Start () {
     start_x = transform.position.x;
     attribs = GetComponent(NPC_set_attributes); // get the script
     range = attribs.npc_patrolling_range;
 }
 
 function Update () {
     transform.Translate(Vector3(attibs.npc_move_speed*Time.deltaTime, 0.0, 0.0), Space.World);
     if(transform.position.x >= start_x + range){
         Change_direction();
     } else if(transform.position.x <= start_x-range) {
         Change_direction();
     }
 }
 
 function Change_direction () {
     attribs.npc_move_speed = -attribs.npc_move_speed;
     attribs.npc_facing_left = !attribs.npc_facing_left;
 }

moving object on x axis without affecting z axis

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