I want to know in Unity3d has relative souce file like Unreal Engine?

some thing like this.

 

I have no idea what a relative source file does. Lazy googling hasn't really revealed anything for me. Care to elaborate on what it does, and then we can tell you how to accomplish the equivalent in Unity.

 

I believe this is referring to relative vs. absolute paths.

From wikipedia:

So an absolute path might be "C:\Projects\YourGame\Assets\Textures\whatever.png", whereas a relative path will be something like "..\Textures\whatever.png".

As for Unity, since you can move project folders around and everything still works it's clearly not using absolute paths in the classic sense. My guess is that all paths are stored relative to the project's root directory, but it's honestly never mattered to me so I've never checked.

 

Paths to assets are stored in the asset database. (I would assume relative, internally). But, pathing is not critical as it’s handled by the asset database. For external files, it’s absolute.

 

From what I understand unity uses the GUIDs and not the paths at all, which is why you need to move things inside of the Unity editor if you want it to continued working

 

Yes, (ish). The guid is the unique identifier for an ement’s entry in the AssetDatabase. The path to assets location is stored there. When you move something in the editor the path is updated. If you move outside of that, the path isn’t updated and broken.

 

To get full or relative path:

Code (CSharp):

1.  
2.         public GameObject thingToFind;
3.        
4.         public void ShowPath()
5.         {
6.             var path = AssetDatabase.GetAssetPath(thingToFind);
7.             var assets = Application.dataPath.Replace("/Assets", "");
8.             // relative to Assets folder
9.             Debug.Log(path);
10.             // full path
11.             Debug.Log(assets+"/"+path);  
12.         }
13.  
14.  

Result:

 

This. It's easy to verify too. Simply create a blank project in the newer releases of Unity, open the AssetDatabase binary file in a text editor (like Visual Studio Code), and search for the name of the scene file that the latest release generates with a blank project.

 

Unity is designed in a manner where you as the game developer should not need to be concerned with the path of your source files in most cases, as you access them through references established in the editor's inspector starting from objects (and their attached components) you place in a scene rather than from their file path on disk. This is regardless of how the information is tracked by Unity internally (interesting discussion above though).

A couple exceptions are when loading assets at runtime either from a Resources folder or from an Asset Bundle, where you can use a relative path to the asset from its Resources folder or of the asset bundle respectively, not their absolute path on disk.

https://docs.unity3d.com/ScriptReference/Resources.Load.html
https://docs.unity3d.com/ScriptReference/AssetBundle.LoadAsset.html