What is wrong with this code ?

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Hereunder is he health bar code I have for my units (a green bar floating above the units - RTS style). The problem is that the bar does not stick to the unit (or move together with it). In the second i move the camera the health bar moves in that direction.

Can you please help ?

     using UnityEngine;
     using System.Collections;
      
      
     public class AIHealth : MonoBehaviour {
     public int maxHp;
     public int currentHp;
     public Camera mainCamera;
     public Texture2D hpBarBG;
     public Texture2D hpBarCurrent;
         public Transform target; 
      
     private float offsetY;
      
     //script will be atached to each GameObject that can suffer dmg.
     void Start () {
     //put it on top of the character
     offsetY=gameObject.collider.bounds.size.y-2;
     Debug.Log(offsetY);
     }
      
     void Update () {
             health h=(health)GetComponent("health");
             h.currenthealth = currentHp;
             h.maxhealth = maxHp;
             var wantedPos = Camera.main.WorldToViewportPoint (target.position);
          transform.position = wantedPos; 
     }
      
     void OnGUI(){
     //the hp bar background location on screen
     Rect rcBg = new Rect(0,0,60,14);
     //the current HP bar
     Rect rcCurrent = new Rect(0,0,((currentHp)/maxHp)*56,8);
      
     //the important part : where this object is located in my screen
     Vector3 point = mainCamera.WorldToScreenPoint(new Vector3(
     transform.position.x,
     transform.position.y+offsetY,
     transform.position.z)
     );
      
     //had to add the substraction since my Y axis were revesed (
     rcBg.y = Screen.height-point.y;
      
     //do some ugly hardcoding so the bar is pretty and centered
     rcBg.x = point.x-30;
     rcCurrent.x=rcBg.x+2;
     rcCurrent.y=rcBg.y+3;
     GUI.DrawTexture(rcBg,hpBarBG);
     GUI.DrawTexture(rcCurrent,hpBarCurrent);
      
     }
      
     }

Answer 1

Best Answer

Answer by Chronos-L · Jun 06, 2013 at 07:38 AM

The combination of these lines is creating the problem:

 var wantedPos = Camera.main.WorldToViewportPoint (target.position);
 transform.position = wantedPos; 
 
 ...
 
 //the important part : where this object is located in my screen
 Vector3 point = mainCamera.WorldToScreenPoint(new Vector3(
 transform.position.x,
 transform.position.y+offsetY,
 transform.position.z)
 );

The calculation, setting the transform.position to a viewportPoint, doesn't makes sense to me. I clean up some of the lines, attached the script to a simple cube, and I got a working health bar right under the cube.

 using UnityEngine;
 using System.Collections;
 
 public class AIHealth : MonoBehaviour {
     public int maxHp;
     public int currentHp;
     public Texture2D hpBarBG;
     public Texture2D hpBarCurrent;
     
     private float offsetY;
     
     void Start () {
         offsetY=gameObject.collider.bounds.size.y-2;
     }
     
     void Update () {
         //I commented these 3 lines out when I tested it
         health h=(health)GetComponent("health");
         h.currenthealth = currentHp;
         h.maxhealth = maxHp;
         
         //Removed the 2 line here, they are screwing things up
     }
     
     void OnGUI(){
         Rect rcBg = new Rect(0,0,60,14);
         
         //Fixed this: added in the 1.0f to correct the calculation
         Rect rcCurrent = new Rect(0,0,((currentHp)*1.0f/maxHp)*56,8);
         
         //Just a simple clean up
         Vector3 point = Camera.main.WorldToScreenPoint(
             transform.position + Vector3.up * offsetY
         );
         
         //Everything else are the same from here on
         ...
     }
 }

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primus88 · Jun 06, 2013 at 07:54 AM 0

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I receive each frame :

NullReferenceException UnityEngine.Camera.WorldToScreenPoint (Vector3 position) (at C:/BuildAgent/work/7535de4ca26c26ac/Runtime/ExportGenerated/Editor/UnityEngineCamera.cs:327) AIHealth.OnGUI () (at Assets/$$anonymous$$yScripts/AIHealth.cs:32)

FOR :

Vector3 point = Camera.main.WorldToScreenPoint(transform.position + Vector3.up * offsetY);

I attached the script to my unit.

Chronos-L · Jun 06, 2013 at 08:00 AM 0

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Do you have a legit main camera in your scene?

http://docs.unity3d.com/Documentation/ScriptReference/Camera-main.html

primus88 · Jun 06, 2013 at 08:02 AM 0

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I forgot that I have to attach a camera because using the default setting wouldn't find my camera... Yeah I sorted it out. It looks ok now. Still doing some tests.

primus88 · Jun 06, 2013 at 08:10 AM 0

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Ok, works almost perfect. Why almost ? Because it works great if I attach the script to an existent game object, but if I do the same thing by attaching it to a prefab then spawning it, if the spawned objects move, the hb doesn't. It remain in the same place.

Help ?

Chronos-L · Jun 06, 2013 at 09:35 AM 0

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if I do the same thing by attaching it to a prefab then spawning it, if the spawned objects move, the hb doesn't.

I wrote a simple script to do the same and it is working fine at my machine, I can spawn a tons of object and move them anywhere I want and there is no problem.

It remain in the same place.

Is there any runtime error?

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