Btw, they don't just refactor the game with a new rendering engine.
The Unreal-Project is something entirely new, it's a completely different game. A free roaming 3D environment can't be compared to just showing images one after another And there is a lot - and I really mean a LOT - more animations to do than in everything we saw so far.
A real free roaming 3D environment cannot be done by rendering in advance
any possible 2D frame like the current game we are commenting in this thread. Or 100 terabytes would not be enough to contain all the possible frames, and the algorithm to choose the correct sequence of frames according to the movement of the virtual camera would be more complicated than the rendering algorithm itself...
...I think that the only way to do it is runtime rendering (or at most you can render in advance some basic positions of the bodies, but then use them as 3D sprites that you still have to project in 2D to decide which pixels should be lit), and this requires the player to own a very powerful machine... IDK how many of us are willing to invest 5k $ just to play a porn virtual reality game.
This technology will be available and it will make big money... But only when the top shelf user hardware will cost no more than 1k $, and medium-level 500$... By now it appears to be premature.
As you said, it's a completely different technology. People want new contents on new technology, not adaptations of old contents born in a different technology.
The first 3D games to be successful were Doom and Tomb Raider. Before them, 3D CGI was used to adapt PacMan in 3D, but it was never a success: same as 2D pacman but you could also jump over the ghosts to avoid them. Bummer.
This is going to be the same: I don't care if I can roam the house freely in 3D if the NPC just remain freezed in their position when it's not their turn to interact with the MC.
Can you hear that damned buzzer noise when you click on a NPC and the system replies "I don't need to talk her now"?
To exploit a 3D free roaming environment NPCs should act like in Doom, or Tomb Raider, or whatever young people play nowadays in a non porn game.
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By the way, this is the reason why in current version movements in animations appear reasonably natural, while the walking Megan in the preview appears to be more robotic than the movements of Lara Croft in the first Tomb Raider in the Nineties: because if you render in advance a 3D animation
a) only the developers must have cutting edge machines, and the user is ready to go with a medium level machine
b) you can make any needed calculation, because it's not a problem if rendering a 5-minute animation takes 1 hour of computing time, if the result is more realistic.