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If you've ever wanted to be a Virtual Reality (VR) Spectator (from a third-person perspective) while others are interacting with a VR environment (from a first-person perspective), then Unreal Engine 4's (UE4) VR Spectator Screen is the ideal feature for you. While running the VR Spectator Screen, you'll be able to observe other players with your computer monitor (or television), which is valuable when you're gathering feedback on an immersive VR experience.

_{Images Courtesy of GhostPaint.com}

On the left side, you (the spectator) are watching this artist paint a brick wall in VR, while on the right side, the artist is focusing on the painting in VR.

Depending on the Head Mounted Display (HMD) manufacturer, a VR Spectator Screen could be synonymous with a VR Social Screen; or VR Spectator Mode could be synonymous with VR Mirror Mode. Within the context of this documentation, the Spectator Screen is a standard output device (such as a computer monitor or television) that is connected to a VR device. Additionally, enabling Spectator Mode means that you can observe (or, in certain scenarios, interact) with the VR experience while a player uses a HMD in a VR environment.

Supported Platforms

The following platforms currently support Spectator Screen Mode in UE4:

• HTC Vive

• Oculus Rift
  

• Steam VR

• PlayStation VR (PS VR)

Although we expect this feature to be supported by other personal computing devices and consoles, we don't anticipate Mobile VR devices (platforms) to support this feature.

Getting Started with Spectator Screen Mode

When working with textures in Spectator Screen Mode, the upper left coordinate represents minimum coordinate values, while the lower right coordinate represents maximum coordinate values.

Spectator Screen Blueprint Nodes

For the Example Usage, we're using the following Blueprint interface:

Example Usage

1. Go ahead and set up a VR project for one of the platforms that support a Spectator Screen.

2. Now, you'll want to create a new Blueprint script, specifying the image that you want to render to the Spectator Screen. For illustrative purposes, the following Blueprint nodes respond to three Keyboard inputs:

   1. For example, when the 1 key is pressed, this first Blueprint node specifies a static texture, which will be drawn in the Texture area.

   2. When the 2 key is pressed, this second Blueprint node specifies a layout where the HMD eye view is being drawn to the entire screen (with the Texture being drawn in the upper left quadrant of the screen). Additionally, this node specifies the Texture layout while making sure to draw the Eye layout first.

      The Eye and Texture rectangle minimum and maximum values are normalized between [0.0, 1.0] .

   3. Finally, when the 3 key is pressed, this third Blueprint node enables (thereby switching to) TexturePlusEye mode.

End Result

In summary, your new Blueprint sets the Spectator Screen's Texture (along with its Eye and Texture layout) along with the Spectator Screen Mode that you'd like to use.

Although the Texture can serve as a render target (which you can write to from a SceneCaptureComponent2D ), or a container for User Interface elements, it's important to note that SceneCapture can be computationally expensive.

Switching Modes

If you'd like to switch to a new Spectator Screen Mode, you can open the Console and input vr.SpectatorScreenMode Value . For example, entering vr.SpectatorScreenMode 2 enables Distorted mode, which is currently supported by Oculus Rift.

Supported Modes

Depending on your platform, certain Screen Spectator Modes are supported, including the following:

Optimizing Spectator Screen Mode

Currently, there is no standard optimization setting for Spectator Screen mode. If you'd like to implement your own optimization solution for Spectator Screen mode, it's recommended to perform scene captures at 30 fps (assuming your VR application is running at 60, 90, or 120 fps). Additionally, it's recommended to limit the Spectator Screen output to 30 fps. Please be aware that if you attempt to limit Spectator Screen output on certain hardware, you might run into rendering issues if the VR framerate is running at 90 fps (basically, every third frame will be dropped).

Currently Known Issues for Version 4.17

• RenderTargets created at runtime are not assigned as the Spectator Texture until one frame has passed, thereby silently failing until the application's first frame has already been rendered.

• Currently, if a RenderTarget is destroyed (released) while being assigned as the Spectator Texture, the application might crash.