Fade GUITexture

Questions & Answers
1

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:

  1. How do I fade the battery meter GUI texture based on the value of curBattHealth?
  2. What’s the code for draining the battery over time? The code I have doesn’t seem to do anything.
  3. If the flashlight is off, do I need to add code to stop the battery from draining?
  4. 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.

2

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.