Efficient Health Bar

Question

I implemented the Health Bar solution found here: http://answers.unity3d.com/questions/4456 for health bars. The problem is, once I get 4 or 5 instances of the health bars on the screen the frames per second is down a good amount.

For a single bar it might be fine, but for a larger number it doesn't appear to be viable. Any recommendations?

Edit: Found a code problem which helped... but I still wonder if there is a quicker way to draw the bars.

Answer 1

Answer by Loius · Dec 17, 2010 at 09:08 PM

Calling OnGUI from multiple objects might be the culprit. Try assembling a group of healthbars into an array and only having one handler object run OnGUI over those objects.

Something like this pair - Create exactly one Healthbars object and any number of LivingThing objects.

LivingThing.js

var health : float; var maxhealth : float;

function Start() {
  Healthbars.AddBar( this );
}

Healthbars.js

static var healthbars : Array(); static var instance : Healthbars;

function Start() {  
  if ( instance ) throw ("Duplicate Healthbars instance: " + gameObject.name );
  instance = this;
}

static function AddBar( lt : LivingThing ) {
  healthbars.Add( lt );
}

function OnGUI() {
 for ( var lt : LivingThing in healthbars ) {
   // display code goes here
 }
}

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Ejlersen · Dec 18, 2010 at 09:33 PM 0

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Good example, but one thing about the code makes me a bit confused. Its the "for(var lt : LivingThing in healthbars)". I only code in C# in Unity, but that looks very much like a foreach. They are quite expensive, since they have to check the type of each element in the array. But okay, that may not be a problem in javascript, however isen't there something with for-in in javascript that iterates through the array abitrarily? That might give a weird effect on the screen, if the healthbars are on top of each other.

Loius · Dec 20, 2010 at 03:28 PM 0

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It goes through the array in order. If speed is a problem, you can use a builtin array (square brackets), but you'll have to manually resize that yourself. If your healthbars are added in an arbitrary order (which they're pretty much guaranteed to be), and that creates problems, you'll have to arrange the healthbars somehow to not overwrite each other, either by noting what screen space is taken up by already-drawn ones and rearranging the others, or by using some other form of control. Honestly it might be better to use actual healthbar objects to display health if you worry about overlap.

Efficient Health Bar

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