Just realized what causes that: the capture component FOV is too low (I think it’s the default 90 Degrees?) If you up the capture component FOV to 130 degrees you won’t have those edge problems at the cost of lower resolution. This can be implement via blueprint e.g.
That said this fov will vary with HMDs in the future so a complete solution would likely need to be done in the c++ layer, probably adjusting it somewhere here: https://github.com/FreetimeStudio/PortalPlugin/blob/master/Plugins/PortalPlugin/Source/PortalPlugin/Private/PortalFunctionLibrary.cpp#L89 this would also likely fix the portal/hmd fov mismatch that currently exists (notice how the portal floor doesn’t appear to align with the perspective of the floor outside).
Another good addition would be an easy way to specify the resolution of the portal being captured to compensate for loss in resolution or to be able to dynamically adapt to heavy scenes while maintaining a good framerate.