Object Creation (29128)

Questions & Answers
1

I have a problem that I cannot seem to solve. I want to fetch a file or files from a URL and parse each line in said file(s) to create new objects in my game.

A line looks like this:

rock_001,1.5,0,.01,0,0,0,1,1,1

where
rock_001 is the prefab name

the next 3 elements (1.5,0,.01) are the position

the 2nd set of 3 elements (0,0,0) is the rotation

and the 3rd set of 3 elements (1,1,1) is the scale

I’ve successfully fetched and parsed the file from the URL then I pass it off to the following function.

I have the following code that works but it basically creates an empty game object (object with no substance - mesh, colliders, and certainly not the prefab as defined by info[0], etc).What I’m having difficulties with is info[0] contains the “rock_001” value in which I have a prefab called that. Is there a way to instantiate this prefab? I would rather not create giant if else/case statement for all the prefabs possibilities.

static function CreateObject(line : String) {

    // define the variables
	var position : Vector3;
	var rotation : Quaternion;

    // parse the line into it's elements
	var info = line.Split(","[0]);

    // simple debug output to verify elements of the input line
	for(var i = 0;i<info.length;i++) {
		Debug.Log("info["+i+"]: "+info*);*
  • }*

// define variables based on the input line

  • var newObj : GameObject = new GameObject(info[0]);*
  • var px : float = parseFloat(info[1]);*
  • var py : float = parseFloat(info[2]);*
  • var pz : float = parseFloat(info[3]);*
  • var rx : float = parseFloat(info[4]);*
  • var ry : float = parseFloat(info[5]);*
  • var rz : float = parseFloat(info[6]);*

//create position and rotation based on the input line elements

  • position = Vector3(px,py,pz);*
    rotation = Quaternion.Euler(rx,ry,rz);

//assign the position and rotation to the new object

  • newObj.transform.position = position;*

  • newObj.transform.rotation = rotation;*

  • Debug.Log("newObj: "+newObj.ToString);*
    }

3

If you place your prefabs in a folder called ‘Resources’ you can load them dyamicly like this:

 var rock:GameObject = Recources.Load("rock_001");

Where ‘rock_001’ is the name of the prefab you want to load. Read this part of the documentation.

2

It appears that you are looking for either a [Hashtable][1] or a [Dictionary][2]. These are collections of objects that allow you to access them based on a key (usually a string - hey look at that)

Advantages to these types of data structures:

  • Can store a varibable number of Objects
  • You can refer to each object via a string, for example “rock_001”
  • Finding, adding, removing, retrieving elements from the list is easy and efficient

Keep in mind that these have a very high memory overhead in their use.

The example code in the linked reference (near the bottom) is written in C#, so here’s how to create and work with a Hashtable in Javascript:

import System.Collections.Hashtable;
var prefabs : Hashtable = new Hashtable();
var rockPrefab : GameObject;

function Start()
{    
    addEntry( "rock_001", rockPrefab); 
    Debug.Log(  (prefabs["rock_001"] as GameObject).name  );
}

function addEntry( key : String, value : GameObject)
{    prefabs[key] = value;    }

function createObject( name : String )
{
    Instantiate( prefabs[name] as GameObject, transform.position, transform.rotation);
}

One thing you have to be careful about using Hashtables is that you ONLY use one type of objects as keys (String) and that you ONLY put one type of object into it (choose GameObject or Transform and stick with), and that you ALWAYS cast the result of the Hashtable to the correct type of object.

The Dictionary takes care of this problem by using Generics (see the example code at the bottom of the links). The Dictionary makes sure that you never accidentally put a Rigidbody in where a Transfrom should be.
[1]: Hashtable Class (System.Collections) | Microsoft Learn
[2]: Dictionary<TKey,TValue> Class (System.Collections.Generic) | Microsoft Learn