Developer Resources

1. 01Enable Unity OpenXR

   Configure the Unity project for Steam Frame by following Valve’s Unity integration guide.

2. 02Preserve output alpha

   Set the Camera component to clear to transparent black, remove any skybox or opaque background, and ensure rendering effects preserve alpha through to the compositor.

3. 03Request alpha blending

   Add EnvironmentBlendFeature.cs below and enable “Arcturus: Environment Blend” in the Android OpenXR feature settings. The feature applies the required blend mode when the OpenXR session starts.

   EnvironmentBlendFeature.cs

   Copy code

   using UnityEngine;
   using UnityEngine.XR.OpenXR.Features;
   using UnityEngine.XR.OpenXR.NativeTypes;
   #if UNITY_EDITOR
   using UnityEditor;
   using UnityEditor.XR.OpenXR.Features;
   #endif
   
   namespace Arcturus.Passthrough
   {
       // Reusable part of the sample. No camera textures or vendor passthrough extension.
   #if UNITY_EDITOR
       [UnityEditor.XR.OpenXR.Features.OpenXRFeature(UiName = "Arcturus: Environment Blend",
           Desc = "Request core OpenXR alpha blending for compositor passthrough.",
           Company = "Arcturus", Version = "0.1.0",
           FeatureId = "vision.arcturus.sample.environment-blend",
           BuildTargetGroups = new[] { BuildTargetGroup.Android, BuildTargetGroup.Standalone })]
   #endif
       public sealed class EnvironmentBlendFeature : OpenXRFeature
       {
           public bool SessionRunning { get; private set; }
           public bool PassthroughRequested { get; private set; } = true;
           public XrEnvironmentBlendMode ReportedMode => GetEnvironmentBlendMode();
   
           protected override void OnSessionBegin(ulong session)
           {
               SessionRunning = true;
               Apply();
           }
   
           protected override void OnSessionEnd(ulong session) => SessionRunning = false;
           protected override void OnSessionDestroy(ulong session) => SessionRunning = false;
           protected override void OnInstanceDestroy(ulong instance) => SessionRunning = false;
   
           public void RequestPassthrough(bool enabled)
           {
               PassthroughRequested = enabled;
               if (SessionRunning) Apply();
           }
   
           void Apply()
           {
               var mode = PassthroughRequested ? XrEnvironmentBlendMode.AlphaBlend : XrEnvironmentBlendMode.Opaque;
               SetEnvironmentBlendMode(mode);
               // The native plugin applies this asynchronously. Read the reported mode later.
               Debug.Log($"[Passthrough] Requested {mode}; waiting for native submission.");
           }
       }
   }
   

using Arcturus.Passthrough;
using UnityEngine.XR.OpenXR;

var feature = OpenXRSettings.Instance
    .GetFeature<EnvironmentBlendFeature>();
feature.RequestPassthrough(true);

Reference docs