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freshworks
Member
Hi,
Today ive bought a game called braid. The game is very genieus because of the rewind effect. In game you need to solve puzzles by sometime rewind the scene. Also you can't die cause of the rewind effect :)
The technic used is awesome. Does anybody know of this technic or have any idea of how to implement this into a game?
Storing all positions in arrays or :) ?
Link to video : http://braid-game.com/
Cheers,
Jespar
Ok I have no idea how they did it but the way it works in my head is as follows:
Think of your current world and think of this second as a state in time. Freeze it and you have all the information about this state in space. Position, energy, age, whatever.
I guess what I'd do is through every frame I'd save the state of the game universe in an array (of course you'd have to cap it, say saving like a minute at most or something) and rewinding would simply mean traversing backwards in your array through the previous states in the game universe. When you stop, you have a state, with all the needed information of the game universe so you can just start from there.
You'd probably have some main classes which imports everything else and handles the actual view of the screen and saving states would simply mean saving a COPY of the pointer to that main class. It wouldn't even kill memory because all you're saving is a pointer.
The key word is COPY. Because if you save the pointer alone then that element of the array will point to the current working main class so you couldn't actually rewind, copying it and storing the pointer essentially freezes the state in the game universe and you can reference it again in the future.
I hope that made sense and I've actually never done this, the logistics make sense in my head. I'm sorry if it's completely wrong and undoable lol.
BRAID is very well executed. I've done a game with the ability to rewind time and I can say that simply storing the positions/orientations of your objects is not enough. There are many other things to remember. Here's a couple:
- Random number generation seeds (so that if you fast forward all code using random numbers will get the same results and produce the same effect).
- Internal states for objects (e.g. going forward your character is in the RUNNING state, you then rewind, but forget to set him back to STANDING, now when you go forward again he's in a different state than he was originally).
If I were going to do it again I would design my game to be extremely Object Oriented (i.e. very few structs). I would then have all of my objects implement some sort of serialization scheme so that I could simply at the end of each frame ask everything important to serialize itself into a buffer. I could then compress this buffer in memory for later restoration.
I would also design all of my gameplay to not be reliant on things happening in order. I.e. it should not be a problem to instantly set my character to the RUNNING state, the logic should not require him to be in the STANDING state before I can set him to the RUNNING state. This would allow extreme flexibility, and allow me to have a buffer of arbitrary length (I don't have to worry about something important falling off the back of the buffer).
As long as you know you're going to do it, then it's not too bad as long as you design your game well.
IMO one of the things Braid did excellently is the reversal of their audio. You don't usually see that in games that allow you to rewind time.
Braid is a fantastic game on many levels. The rewind was executed flawlessly and the art direction was top notch. I loved playing it... Huge fan!
The project I am working on has a recording system for characters and clones of the character for playback. Very different in nature to Braid in the sense that you play the same segment of time with multiple clones instead of rewinding.. ie play for a set period of time with character 1, then it restarts and you can see character 1 do everything you did before while you play character 2, then character 3, etc. I can second Stormtap's comments about rewind not being trivial. It seems every time I think I have everything in regards to character and object states recorded for proper playback I find the next dozen things I need to consider.
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