How to prevent the player to move beyond certain x-position value

Question

Hey,

I'm pretty new to Unity and I'm currently working on a 3D asteroid evasion game. The player is piloting a ship through an asteroid field. The ship moves constantly forward and the player can only navigate up, down, left and right. As I don't want to make an infinite asteroid field, I want my player to stay inside the field and stop him from moving out of it. The field goes from -10 to 10 on the X and -10 to 10 on the Y. I want to track the player position and if he moves past the -10 or 10 on the X position, his x-position should be set to 10 (or -10). Same on the Y-position. Any idea on how to do that in C#?

Thanks and best, Mat

Answer 1

Ok I've got it to work now.

this is the final, working code:

 using UnityEngine;
 
 public class PlayerMovement : MonoBehaviour {
 
     public Rigidbody player;
 
     public float forwardForce = 2000f;
     public float sidewaysForce = 500f;
     void SetTransformX(float n)
     {
         player.transform.position = new Vector3(n, player.transform.position.y, player.transform.position.z);
     }
     void SetTransformY(float n)
     {
         player.transform.position = new Vector3(player.transform.position.x, n, player.transform.position.z);
     }
 
     // Update is called once per frame
     void FixedUpdate () {
 
         player.AddForce(0, 0, forwardForce * Time.deltaTime);
 
         if (Input.GetKey("d"))
         {
             player.AddForce(sidewaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
            
         }
 
         if (Input.GetKey("a"))
         {
             player.AddForce(-sidewaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
           
         }
 
         if (Input.GetKey("w"))
         {
             player.AddForce(0, sidewaysForce * Time.deltaTime, 0, ForceMode.VelocityChange);
         }
 
         if (Input.GetKey("s"))
         {
             player.AddForce(0, -sidewaysForce * Time.deltaTime, 0, ForceMode.VelocityChange);
         }
         if (player.transform.position.x >= 10) { SetTransformX(10.0f); player.velocity = new Vector3(0, player.velocity.y, player.velocity.z); }
         if (player.transform.position.x <= -10) { SetTransformX(-10.0f); player.velocity = new Vector3(0, player.velocity.z, player.velocity.z); }
         if (player.transform.position.y <= 0) { SetTransformY(0.0f); player.velocity = new Vector3(player.velocity.x, 0, player.velocity.z); }
         if (player.transform.position.y >= 10) { SetTransformY(10.0f); player.velocity = new Vector3(player.velocity.x, 0, player.velocity.z); }
     }
 }

--- old response ---

Ok, I might need to clarify my struggle a bit. I understand the code you guys posted and that is also what I had in mind, but I don't know how to do it with the code I currently have.
This is my current player movement code:

 using UnityEngine;
 
 public class PlayerMovement : MonoBehaviour {
 
     public Rigidbody player;
 
     public float forwardForce = 2000f;
     public float sidewaysForce = 500f;
     // Update is called once per frame
     void FixedUpdate () {
 
         player.AddForce(0, 0, forwardForce * Time.deltaTime);
 
         if (Input.GetKey("d"))
         {
             player.AddForce(sidewaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
             player.transform.Rotate(0, 0, 20 * Time.deltaTime);
         }
 
         if (Input.GetKey("a"))
         {
             player.AddForce(-sidewaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
             player.transform.Rotate(0, 0, -20 * Time.deltaTime);
         }
 
         if (Input.GetKey("w"))
         {
             player.AddForce(0, sidewaysForce * Time.deltaTime, 0, ForceMode.VelocityChange);
         }
 
         if (Input.GetKey("s"))
         {
             player.AddForce(0, -sidewaysForce * Time.deltaTime, 0, ForceMode.VelocityChange);
         }
 
     }
 }

If I use this simple code-snippet:

 if (player.transform.position.x >= 10) { player.transform.position.x = 10; }

Visual Studio gives me the following error:

player.transform.position.x is not a variable and therefore cannot be changed

so this seems not to work... :-/

Answer 2

Answer by Pandaa2610 · Feb 18, 2018 at 02:02 PM

You answered your own question,Just write:

If (transform.position.x < 10) { transform.position.x = 10 }

Four times for x,y axis (Positive and negative value)

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Answer 3

Answer by yokenstein · Feb 18, 2018 at 02:08 PM

You can do this 2 ways: 1) use colliders and place them on the boundaries of your screen (make sure they're not isTrigger). This will be easier and a more preferable way to do it 2) in code, you could set constraints of your spaceship:

 if(transform.position.x > 10) 
 {
      transform.position.x = 10;
 }
 else if(transform.position.x < -10)
 {
      transform.position.x = -10;
 }
 
 if(transform.position.y > 10)
 {
     transform.position.y = 10;
 }
 else if(transform.position.y < -10)
 {
     transform.position.y = -10;
 }

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How to prevent the player to move beyond certain x-position value

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