When you wear a mixed reality headset, it becomes the center of your holographic world. The Unity Camera component will automatically handle stereoscopic rendering and will follow your head movement and rotation when your project has "Virtual Reality Supported" selected with "Windows Mixed Reality" as the device (in the Other Settings section of the Windows Store Player Settings). This may be listed as "Windows Holographic" in some versions of Unity.
However, the following settings should be manually applied to the cameras in your app to optimize it for your holographic experience:
Note: These settings need to be applied to the Camera in each scene of your app.
By default, when you create a new scene in Unity, it will contain a Main Camera GameObject in the Hierarchy which includes the Camera component but does not have the above settings properly applied.
The default settings on the Unity Camera component are for traditional 3D applications which need a skybox-like background as they don't have a real world.
You can use script code to determine at runtime whether the headset is immersive or holographic by checking HolographicSettings.IsDisplayOpaque.
It will be easier to lay out your app if you imagine the starting position of the user as (X: 0, Y: 0, Z: 0). Since the Main Camera is tracking movement of the user's head, the starting position of the user can be set by setting the starting position of the Main Camera.
Rendering content too close to the user can be uncomfortable in mixed reality. You can adjust the near and far clip planes on the Camera component.
When there are multiple Camera components in the scene, Unity knows which camera to use for stereoscopic rendering and head tracking by checking which GameObject has the MainCamera tag.