Actually, I just had another idea that I can try, which is a combination of a tutorial about crossfading cameras and everything I have seen on how the portals were made in the portal games. I could try streaming the surface level in a separate area. A second camera and a fake player model would be mimicking the rotation of the true camera and player above the area where the flat map will stream in. The second camera’s location over the flat-level would be determined by some math I will have to figure out that would convert the polar coordinates of where the player is in relation to the planet’s sphere to a spot over the flat map. As the player gets close enough, the flat level would stream in and a crossfade would start from the main camera to the second camera and, when the fade finishes, the main camera, and the player would be teleported to the exact locations of the fake player and second camera which would then be disabled until they are needed again.