Question by Arthur_Gentz · May 05, 2021 at 04:30 PM · performance tag caching

Is it okay to assign and 'un-assign' game object tags at runtime, will it come back to bite me?

Does assigning/'un-assigning' a game object's tag have some 'scene recalculation' penalty? Or can i assign/'un-assign' tags willy-nilly?

I'm working on some interactivity between objects in the scene, and the interactivity has become a great big web. The initiation of interactions relies on identifying initiates by their tags.

The methods of 'halting' interactivity between objects during certain scenarios has reached a level of complexity that I don't want to add upon.

After some thought, the simplest way forward seems to be the simple setting/'unsetting' of tags of the interaction initiating game objects. Which would allow my current setup to easily handle enabling/disabling of any number of concurrent interactions.

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Llama_w_2Ls · May 05, 2021 at 07:23 PM 0

AFAIK, tags are just meta-data assigned to a game object, that specify a reference word for a group of objects.

Assigning this meta-data would likely have a very $$anonymous$$imal impact on performance, so assigning tags on a large scale very rapidly, doesn't seem to have a major impact.

There is no scene recalculation penalty, I believe. When you use tag functions such as FindObjectWithTag or CompareTag, it reads the meta-data directly from the game object. The objects with certain tags aren't kept in some special list (afaik), and so there is no scene recalculations done.

You could try a stress test yourself that creates a bunch of empty objects, assigns random tags every update, and checks the time it takes to find a random object by tag, and see if the frame rate is impacted by this in any way, for example:

 public class StressTest : MonoBehaviour
 {
     public int Entities;
     public string[] Tags;
 
     GameObject[] EntityArray;
 
     void Update()
     {
         print(System.DateTime.Now.ToString());

         EntityArray = new GameObject[Entities];
 
         for (int i = 0; i < Entities; i++)
         {
             EntityArray[i] = new GameObject(i.ToString())
             {
                 tag = RandomTag
             };
         }
 
         var randomObj = GameObject.FindGameObjectWithTag(RandomTag);
         print(System.DateTime.Now.ToString());

     }
 
     string RandomTag
     {
         get
         {
             return Tags[Random.Range(0, Tags.Length)];
         }
     }
 }