Monoscopic view through HMD

Development Platform & Builds XR Development
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1

Hello everybody,

I am planning an experiment in which I want to investigate the impact of spatial cues on the VR experience.
For this purpose I would like to disable stereoscopic rendering for my VR application. So I would like to have the same image being rendered on both eyes of the HMD.

I use the console command ‘vr.bEnableStereo False’ to do this. However as soon as I trigger this command the HMD is disabled - I see a “Waiting …” sign through the HMD and still parts of the virtual environment.
However the mirror works as expected - the view direction follows the head tracking of the HMD and it switches to only one view. When I switch back to stereo mode the application and the HMD work as expected.

When I try to enable the HMD with the ‘Enable HMD’ node while in monoscopic mode, the application autmoatically goes back to stereoscopic mode.
There seems to be something that prevents the haedset being enabled while not in stereoscopic mode.
I am working with UE 4.27, the HTC Vive Pro and SteamVR.

I already tried out some of the VR specific commands of unreal and I even read through the source code of the SteamVR plugin - but there is nothing that would explain this behavior.

Is there a way to achieve a monoscopic view through the HMD?

2

There isn’t any monoscopic VR rendering support built into Unreal, turning off vr.bEnableStereo will just turn of the VR rendering system.

The easiest way to disable stereo rendering would be to modify the FSteamVRHMD::GetRelativeEyePose() function in the SteamVR plugin to output the same pose for both eyes. As a bonus that would also give you full control over the eye position. The eye offset has a huge impact on spatial cues from parallax when rotating the head, so choosing a good position for a single eye would be important.