Great job on your portal work, EgoMoose! My TARDIS portal demo was based on the exact same principles, though I never resized the viewport due to the same concerns with blurring (not that it worked, if you walked too far away you’d just see blank space).
As it would so happen, in the past week I’ve rewritten the portal with a different method and have reached a near-complete state. It allows for the viewport to maintain quality as it does not need to move nor resize, but issues with perspective come with it that ruin the effect as does blurring.
You can see the warping effect most obviously at the bottom while up close, and in the center while moving left and right, but it is otherwise pretty subtle . I just need some way to distort the viewport’s camera’s rotational matrix so it ‘faces the player’s center of view’, but I don’t understand CFrame matrices enough to do this, or if it’s even technically possible. Might need to ping a CFrame expert like AxisAngles.