UE5 nDisplay Top-Bottom Stereo Viewport size

Hi all

I am trying to create content for a CAVE. I am using Unreal Engine 5.1 with nDisplay. The environment is Linux with nVidia GPUs. Stereo is passive top-bottom layout (similar to left-right side-by-side). X is configured with one 1600x3200 screen stretched vertically across two 2560×1600 monitors.

I managed to package and start a Vulkan for Linux. The window correctly covers the entire screen. Unfortunately, the stereo viewports within the window do not stretch correctly. The width is too large, but the height is too small. This is a screenshot taken from the front node:

This is the nDisplay configuration: NDC_Cave.ndisplay (9.1 KB)

This is the command I use to start the packaged binary with:

./nDisplayTest.sh "" -messaging -dc_cluster -fixedseed -NoVerifyGC -noxrstereo -xrtrackingonly -RemoteControlIsHeadless -StageFriendlyName="node_front" -dc_cfg="NDC_Cave.ndisplay" -dc_dev_top_bottom -dc_node=node_front Log=node_front.log -ini:Engine:[/Script/Engine.Engine]:GameEngine=/Script/DisplayCluster.DisplayClusterGameEngine,[/Script/Engine.Engine]:GameViewportClientClassName=/Script/DisplayCluster.DisplayClusterViewportClient -unattended -handleensurepercent=0 -ExecCmds="DisableAllScreenMessages"
  -WINDOWED -ForceRes WinX=0 WinY=0 ResX=1600 ResY=3200

If using -FULLSCREEN instead of -WINDOWED …, the window will only use one monitor instead of the entire screen.

How can I convince Unreal Engine 5 to keep the viewports at the configured size?

Kind Regards
Hermann

A solution turns out to be „RTFM“: As a workaround, do not use the stereo setting in the switchboard dc_dev_top_bottom, but to use monoscopic rendering dc_dev_mono and an explicit viewport configuration as described here: Stereoscopic Rendering with nDisplay in Unreal Engine | Unreal Engine 5.1 Documentation