Hello,
if you want to have dedicated access to the rendered images for left and right eye using the “ScreenPosition” node in Unreal Engine 4.x you must turn off “Project Settings → Rendering → VR → Instance Stereo”.
At least I can confirm this with HTC Vive and Unreal Engine 4.14.3.
“Instanced Stereo” was introduced in Unreal Engine 4.11 and increases the performance tremendously.
Any ideas how to avoid to turn off “Instanced Stereo” are welcomed.
Best,