Fade GUITexture

Question

This is a multi part question. Sorry if this has been asked before, I've searched for awhile and didn't find what I was looking for.

I'm making a simple meter to represent a battery for a flashlight using two GUI textures(one is just the outline of a battery, the other a gradient of red to green, if it helps).

Here's my code:

 using UnityEngine;
 using System.Collections;
 
 public class HUD : MonoBehaviour {
 
     // various textures to display on screen
     public Texture2D reticle;
     public Texture2D batteryIcon;
     public Texture2D batteryMeter;
 
     public float maxBatteryHealth = 100;        // the max amount of battery health
     public float curBattHealth;                    // the current amount of battery health
     public float batteryDecayRate = 1;            // the rate at which the battery will decay
 
 
     public bool battAreDead = false;            
 
     // Use this for initialization
     void Start () {
 
         curBattHealth = maxBatteryHealth;        // set the current battery health to the max battery health to start
         Screen.showCursor = false;                // Hide the mouse 
     }
 
     void OnGUI()
     {
         // code for the on screen reticle
         float xMin = (Screen.width / 2) - (reticle.width / 2);        // reticle x position
         float yMin = (Screen.height / 2) - (reticle.height / 2);    // reticle y position
         GUI.DrawTexture (new Rect (xMin, yMin, reticle.width, reticle.height), reticle);    // draw the reticle to positions
 
         // Code for the battery icon                
         GUI.DrawTexture (new Rect (1300, 545, batteryIcon.width / 5, batteryIcon.height / 5), batteryIcon);
 
         // Code for the battery meter
         GUI.DrawTexture (new Rect (1300, 545, batteryMeter.width / 5, batteryMeter.height / 5), batteryMeter);
 
     }
 
 
     // Update is called once per frame
     void Update () 
     {
         if (GameObject.Find("flashlight.GetComponent<Flashlight>().flashLightEnabled") == true) // find the flashlight to
                                                                                                 // check if it's on
         {
             curBattHealth -= Time.deltaTime - (batteryDecayRate * 2);    // drain curbattHealth here, the equation is wrong!
 
         }
         else
         {
             // if the flashlight is off, do nothing to the battery
         }
 
         if (curBattHealth <= 0)         
         {
             curBattHealth = 0;
             battAreDead = true;        // if the batteries have no health left they are dead, TO DO: disable the flashlight
         }
     }
 }

Now for the questions:

How do I fade the battery meter GUI texture based on the value of curBattHealth?
What's the code for draining the battery over time? The code I have doesn't seem to do anything.
If the flashlight is off, do I need to add code to stop the battery from draining?
If the flashlight is off, how do I store the curBattHealth?

Pretty new to programming myself so any advice/tips etc. would be greatly appreciated.

Answer 1

Well, I will rewrite your code and I will add comments that you understood responses to your questions:

  using UnityEngine;
  using System.Collections;
 
  public class HUD : MonoBehaviour {
 
   // various textures to display on screen
   public Texture2D reticle;
   public Texture2D batteryIcon;
   public Texture2D batteryMeter;
 
   public float maxBatteryHealth = 100; // the max amount of battery health
   public float curBattHealth; // the current amount of battery health
   public float batteryDecayRate = 1; // the rate at which the battery will decay

   public bool BattAreDead = false;

   // My variable
   public float speedBatt = 10.0f // Speed of fading of the battery 10 unit per second
      
 
   // Use this for initialization
   void Start () {
    curBattHealth = maxBatteryHealth; // set the current battery health to the max battery health to start
    Screen.showCursor = false; // Hide the mouse 
   }
 
   void OnGUI() {
     if (GameObject.Find("flashlight") != null && !battAreDead) { //checks battery object
      // code for the on screen reticle
      float xMin = (Screen.width / 2) - (reticle.width / 2);      // reticle x position
      float yMin = (Screen.height / 2) - (reticle.height / 2);    // reticle y position
      GUI.DrawTexture (new Rect (xMin, yMin, reticle.width, reticle.height), reticle);    // draw the reticle to positions
 
      // Code for the battery icon                
      GUI.DrawTexture (new Rect (1300, 545, batteryIcon.width / 5, batteryIcon.height / 5), batteryIcon);
 
      // Code for the battery meter
      //Fade out battery
      GUI.color = new Color(1.0f, 1.0f, 1.0f, curBattHealth / maxBatteryHealth);
      GUI.DrawTexture (new Rect (1300, 545, batteryMeter.width / 5, batteryMeter.height / 5), batteryMeter);
    }
   }
 
   // Update is called once per frame
   void Update () {
    // In my opinion, it is necessary to find only object battery  
    if (GameObject.Find("flashlight") != null && !battAreDead) { // find the flashlight
     curBattHealth -= speedBatt*Time.deltaTime;   // drain curbattHealth
     if (curBattHealth <= 0) {
      curBattHealth = 0;
      battAreDead = true; //and destroy flashlight
      Destroy(GameObject.Find("flashlight").gameObject);
     }  
    } else { //re-drain battery
     curBattHealth += speedBatt*Time.deltaTime;
     if (curBattHealth >= maxBatteryHealth) {
      curbattHealth = maxBatteryHealth;
      battAreDead =false;
     }
    }
   }
  }

And attach this script to any object (except flashlight object) on scene, for example, MainCamera.

Fade GUITexture

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