How can I make one scene transition into another?

Imagine falling through Jupiter. You would encounter the atmosphere, and it would get darker, and eventually, you would be in a layer of very bright, mirror-ish hot liquid hydrogen that transitions in between the layers kinda like mist.

What I am talking about is blending two scenes together when the player passes between them. How can I do this?

The player must not be duplicated between scenes.

2D wise, making a simple overlay that does these effects, whether through material nodes or post-process scripts is easy enough.

3D wise… that’s a bit more complicated. A simple transition would be that you’ve linked all of the mentioned dynamic elements to animation drivers, or perhaps more logical, game properties. That way you can sync/control the scenes to exact visuals, more or less.

If you want to go mega complex, you could use two overlay scenes together or two cameras w/ two overlay scenes. They’re more complicated to control because of physics and other logical interactions, but it’s doable, if you want. For example here’s my 1v1 demo of two different type of players in legacy UPBGE (still doable in current UPBGE versions) where I controlled what one player saw and what another player saw by separating them with individual scenes and cameras. Left side is first-person view, facing a mostly invisible opponent, while right side has a visible opponent and a third-person view. Inspired by Ubisoft’s famous game mode: Splinter Cell’s, Spies vs. Mercs.