Question Hololens 2 Project: UnityEngine.XR.ARSubsystems and ARFoundation do not exist in UnityEngine.XR

Hello alltogether,

today I encountered an error I could not fix various attempts and research:

In my Unity project for the Hololens 2, I get two errors:
1)
Severity Code Description Project File Line Suppression State
Error CS0234 The type or namespace name 'ARSubsystems' does not exist in the namespace 'UnityEngine.XR' (are you missing an assembly reference?)

2)
Severity Code Description Project File Line Suppression State
Error CS0234 The type or namespace name 'ARFoundation' does not exist in the namespace 'UnityEngine.XR' (are you missing an assembly reference?)

I do not know why, but Unity/VS2022 keeps telling me there are no such packages ARSubsystems and ARFoundation within UnityEngine.XR...

I am using Unity 2021.3.2f1, the packages: OpenXR Plugin 1.4.2, AR Foundation 4.2.3, AR Subsystems 4.2.3, ARCore XR Plugin and ARKit XR Plugin 4.2.3, XR Plugin Management 4.2.1, among some others.

When I type "using UnityEngine.XR." Visual Studion (2022) only proposes "using UnityEngine.XR.WSA" and "using UnityEngine.XR.Provider".

Has anyone any thoughts on this one? I would appreciate it.

Thanks
Robin

 

Thank you for the reply. The error occurs in my own script where I try using ARFoundation and ARSubsystems. I don't have custom assembly definitions.

I tried deleting the library folder having Unity re-import all packages - sadly it did not help.

I would appreciate other thoughts on it. Thank you.

 

Does creating new project with freshly import all packages working without any dependency problem?

If yes, could be there is a script update (automatically, or manually by package manager, idk), which makes the dependency goes wrong.
If no, then might want to re-install the unity engine (not Editor, just engine, e.g., 2022.X.XXX), then re-install the ARFoundation for Hololens 2 from package manager.

Hopefully can help.

 

Thank you for the answers. For some reason which I cannot retrace, the mentioned errors disappeared after I used another project that worked with the packages and migrated my code of the current project to it... awkwardly weird.

However, this created another error:
The type or namespace name 'WindowsMREnvironment' does not exist in the namespace 'UnityEngine.XR.WindowsMR' (are you missing an assembly reference?)

The manifest of the current project looks like this:

{
"dependencies": {
"com.fhgigdvrar.simpleusermenu": "file:../simpleusermenu-master",
"com.microsoft.mixedreality.input": "file:MixedReality/com.microsoft.mixedreality.input-0.9.2006.tgz",
"com.microsoft.mixedreality.openxr": "file:MixedReality/com.microsoft.mixedreality.openxr-1.4.4.tgz",
"com.microsoft.mixedreality.toolkit.extensions": "file:MixedReality/com.microsoft.mixedreality.toolkit.extensions-2.8.2.tgz",
"com.microsoft.mixedreality.toolkit.foundation": "file:MixedReality/com.microsoft.mixedreality.toolkit.foundation-2.8.2.tgz",
"com.microsoft.mixedreality.toolkit.standardassets": "file:MixedReality/com.microsoft.mixedreality.toolkit.standardassets-2.8.2.tgz",
"com.microsoft.mixedreality.toolkit.tools": "file:MixedReality/com.microsoft.mixedreality.toolkit.tools-2.8.2.tgz",
"com.microsoft.mrtk.graphicstools.unity": "file:MixedReality/com.microsoft.mrtk.graphicstools.unity-0.4.0.tgz",
"com.unity.collab-proxy": "1.15.18",
"com.unity.feature.development": "1.0.1",
"com.unity.ide.rider": "3.0.13",
"com.unity.ide.visualstudio": "2.0.14",
"com.unity.ide.vscode": "1.2.5",
"com.unity.test-framework": "1.1.31",
"com.unity.textmeshpro": "3.0.6",
"com.unity.timeline": "1.6.4",
"com.unity.ugui": "1.0.0",
"com.unity.visualscripting": "1.7.6",
"com.unity.xr.arfoundation": "4.2.3",
"com.unity.xr.arkit": "4.2.3",
"com.unity.xr.openxr": "1.4.2",
"org.khronos.unitygltf": "https://github.com/dschie/UnityGLTF.git?path=/UnityGLTF/Assets/UnityGLTF",
"com.unity.modules.ai": "1.0.0",
"com.unity.modules.androidjni": "1.0.0",
"com.unity.modules.animation": "1.0.0",
"com.unity.modules.assetbundle": "1.0.0",
"com.unity.modules.audio": "1.0.0",
"com.unity.modules.cloth": "1.0.0",
"com.unity.modules.director": "1.0.0",
"com.unity.modules.imageconversion": "1.0.0",
"com.unity.modules.imgui": "1.0.0",
"com.unity.modules.jsonserialize": "1.0.0",
"com.unity.modules.particlesystem": "1.0.0",
"com.unity.modules.physics": "1.0.0",
"com.unity.modules.physics2d": "1.0.0",
"com.unity.modules.screencapture": "1.0.0",
"com.unity.modules.terrain": "1.0.0",
"com.unity.modules.terrainphysics": "1.0.0",
"com.unity.modules.tilemap": "1.0.0",
"com.unity.modules.ui": "1.0.0",
"com.unity.modules.uielements": "1.0.0",
"com.unity.modules.umbra": "1.0.0",
"com.unity.modules.unityanalytics": "1.0.0",
"com.unity.modules.unitywebrequest": "1.0.0",
"com.unity.modules.unitywebrequestassetbundle": "1.0.0",
"com.unity.modules.unitywebrequestaudio": "1.0.0",
"com.unity.modules.unitywebrequesttexture": "1.0.0",
"com.unity.modules.unitywebrequestwww": "1.0.0",
"com.unity.modules.vehicles": "1.0.0",
"com.unity.modules.video": "1.0.0",
"com.unity.modules.vr": "1.0.0",
"com.unity.modules.wind": "1.0.0",
"com.unity.modules.xr": "1.0.0"
}
}

 

Currently, I am using Unity 2021.3.2f1.

So I am not quite sure. What would you suggest?

 

This is only my suggestion.
Based on Mr. Ankur said, the Unity 2021 version has some deprecated library, which might be one of the cause of your problem.
If it's possible, I think you can try cloning the project, use the latest Unity 2022 version, then let the Unity update the library from 2021 (previous project) to the newer one.
If it still occur the problem, I might want to remake the project using the latest version, but I know it will be pain.

The terms of remake, not creating all stuffs from scratch.
It's create a fresh new project, then try to migrate scripts, assets, etc., one by one.

Good luck!

 

It means some code in your project references the Windows MR package, which does not exist in 2021 LTS (only up to 2020).

If it's your code, you can try rewriting that part to use the OpenXR package instead. If it's third party code, well...you could try downgrading to 2020 LTS if you don't need any features that are 2021-only.

We're using 2020 LTS for a HoloLens 2 project right now and it works ok so far.