e.g. a 1x1 portal leading into a 1x2 portal, where only the vertical direction is stretched

To make the teleportation seamless, it also requires the player to enter a "stretched view" state.

@qouteall what if the portal transition was animated? So like as you walked through the block size started getting shortened to be able to fit more blocks in your view. The concept of teleporting be changed to "transitioning", currently you're either on one side of the portal or the other. What if instead the portals themselves had an assigned thickness, and depending on how far you are between the edges of the portal fame it would change how much you were in one world or the other. This could make it feel more "real" (as you could watch someone fall through a portal and shrink or grow in real time rather than it happening instantly) also users need to provide the thickness if they want to enable this feature.

We could also control the users opacity to make a really cool "ghost" effect, so let's say they were standing exactly in the middle of a portal, so they're 50% in each world. The user would have two bodies (one in each world), but both of their opacities would be halved. Whichever world the user walked into their opacity would return to normal as they left the portal, but in the other world their body would fade away (like a ghost)

There's also the question of what happens if you look at it from it's side, and I'm not sure what the best answer is but one answer could be to just make the portal invisible from the side (but leave the users inside it visible)

@L1lith It would be cool but it's very hard to implement. It requires a huge refactoring of the mod so it's not being considered for now.

To make the teleportation seamless, it also requires the player to enter a "stretched view" state.