native texture pointer returns 0 in headless build

Question

When I run the following code inside a Unity Editor, or if I build and run it (not in headless mode) GetNativeTexturePtr() returns a value >0 for the texture id, etc.

However, when building the app having a Server Build option enabled GetNativeTexturePtr() always returns 0. Even when IsCreated() returns true.

Any ideas what is happening here?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class test : MonoBehaviour
 {
     private RenderTexture m_RenderTexture;
 
     // Start is called before the first frame update
     void Start()
     {
         m_RenderTexture = new RenderTexture(256, 256, 24, RenderTextureFormat.ARGB32);
         m_RenderTexture.Create();
         RenderTexture.active = m_RenderTexture;
         if (!m_RenderTexture.IsCreated())
         {
             Debug.LogError("RenderTexture could not be created");
         }
         Debug.Log("texture id = " + m_RenderTexture.GetNativeTexturePtr().ToString());
     }
 }

Answer 1

Well, I'm not 100% sure but when you run Unity or a build in headless mode no graphics context is generated at all. In order to create a graphics context you need a window you can draw to (a device context). So in headless mode you don't actually require or use the GPU at all. So of course there would be no native texture pointer since the texture isn't uploaded to the GPU at all. Anything CPU based should still work.

The main issue is probably that almost all default drivers and APIs require a device context which is always bound to some kind of window. If you run in headless mode Unity is supposed to run even in CLI environments without any kind of window support. So it would be difficult to actually accomplish any kind of GPU based rendering.

See this SO question for some insight
This also might be related

If you generally search for GPU rendering in CLI mode you will find a lot blender related posts. However blender mainly uses CUDA or OpenCL for rendering and not the actual GPU rendering pipeline. So I don't think that this possible with Unity. Though I really don't know so this is just a wild guess. Maybe someone from the Unity team could shed some light on this (Maybe @Aras ?)

Answer 2

Answer by Lazuli · Oct 27, 2020 at 08:11 AM

I believe EGL was developed for just such a problem. Is there any way we could convince the Unity team to implement the ability to use an EGL context instead? (Or maybe someone could write a Native plugin..?)

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Answer 3

Answer by avtarsohi · Apr 01 at 05:22 PM

You need to run X11 server for that. Here is the post which will help you: https://towardsdatascience.com/how-to-run-unity-on-amazon-cloud-or-without-monitor-3c10ce022639

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native texture pointer returns 0 in headless build

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