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[Cruxador]

You know, I don't see why people are so down on this. Once interrupted worldgens work from a technical perspective (which they eventually will, there's enough people who want to be able to restart it and advance time) then this will very likely be trivial to implement. Keep in mind he's not suggesting it for Urist McAverageguy, he's suggesting it for gods.
So nobody that isn't player controlled does it, or if they do, nobody ever finds out about it.

Paradox and things are irrelevant - history is remade each time. If you journey to the past, you lose the present. And if you journey a thousand years into the future, you spend a significant portion of that time waiting on worldgen. ot something you'd do all the time, but something a time god should be able to do. Killing your grandfather should do nothing in this case, for simplicities sake.

With these things taken into account, only one criticism remains valid:

This just sounds like, World Gen, the game. For which I say, boo.

Luckily, people who don't want to mess with things like this can merely ignore it.

Indeed, the only real problem with this is that it belongs in the Suggestions forum.

[Mel_Vixen]

The thing we are picky about is that we want to have timetravel affect our game, that if someone else changes time that this change translates to a change for us the player.
 

Paradox and things are irrelevant - history is remade each time. If you journey to the past, you lose the present.

Even with a new branch in the timeline you have the special "meet yourself" problem . For example if the change in the past (like a change on a another continent) of a altered timeline wouldnt change anything in your parallel existence to the point where you meet yourself. It would just be akward how the player double acts etc. and you would need a good number of informations to reconstruct the players state at a given time.

[Soadreqm]

"Traveling to the future" and letting the worldgen run should be both possible and interesting, but it's hardly time travel. And you could restart worldgen and let it run for any time, recreating the past, letting you reverse the game to any point in time before it started. Actually, you can do that right now, but the characters can't. The obvious mechanical problems begin when you want to travel to a point in time where the worldgen was no longer running. Like a time jump of 20 minutes into the past. The game would have to keep detailed track of every player action, and recreate everything every time, which would lead to absolutely obscene loading times and save files ballooning with every keypress. But yeah, that's just an engineering problem, which will be solved when they dicover an automatic hyperthreading code optimization algorithm, letting you run DF on a city-sized cluster. Of course, we'll all be toiling in the Treacle Mines for our insect overlords by then, and won't have time for games, but I'm sure the brood leeches playing Slaves to Armok: Chapter 3: Ant Hive will appreciate the mechanic.

While only giving time travel in increments of centuries to the player playing as a god or something would be easier to do, we'd like all kinds of time powers. I would, at least. Like slowing time down or speeding it up for yourself. Or seeing events that happen in the past or the future. Or jumping to alternate timelines. Or getting an edge in a fight by summoning five copies of yourself from the future (that is, traveling to the past, from the future, when you've already won the fight), and winning a thought-hopeless battle with superior numbers and a stable time loop. Or a magic dagger that lets you anyone who wields it rewind thirty seconds. There's all kinds of stuff you can do with time magic! Or rather, can't.

[alway]

Timeline:
A-------B--------C--D-------E

Say you worldgen starting at A and ending at C. You then proceed to build a fort in time C. After building the fort, you get annoyed at Elves and travel back to time B. You slaughter all elves, triggering a new worldgen. You travel forward in time to D, only to find your fort is no longer there. Unfortunately, since it must trigger a worldgen to figure out the effects of your escapade in time period B, when it gets back to period C, your fort is no longer there since it would be unable to save future events (such as the construction of the fort) without running into extensive paradox problems.
These would range from the simple "dwarf X is a descendant of deceased party member Y and thus can not exist" to more subtle "how did they get the bones of elves who were never born to make those totems?" So it essentially becomes equivalent to worldgen savescumming for it to avoid possibly program crashing paradoxes. Time travel in a game as detailed and emergent as DF is no more useful than a skip X number of years button.
Or in summary: it is impossible, even without pesky relativistic causality rules.

[nenjin]

The self-paradox can be avoided Quantum Leap style. You become yourself at any given point in time, so you can't meet yourself. What's different is now you have foresight. And going to any point in time where you don't exist, you suddenly do. The paradox then becomes internal, and we don't have to worry about it.

I still forsee staring at a motionless screen for three minutes, when you just stab the King's son in the throat, and the game has to recalculate what happened since you just murdered the world's greatest hero.

[alway]

The problem is not self paradoxes: those can be removed with a small wave of the hand. It is the problem of the king's son's son's daughter being the 4th migrant of wave #2 in your fort in the future. And say she is your only mason, who was solely responsible for building both most of your furniture and the blocks for the walls of your entire aboveground fortress. There is no way to just wave that away without it resulting in making either fort mode or the time travel itself pointless.
Or another example: kill off the goblins in the past who in the future came and killed 10 of your fort of 30. Even compensating by resurecting the originally dead dwarfs, it will cause problems in things as mundane as the food and ale supply. No matter how your compensate, it will result in paradoxes which if a magic wand is waved over them in an attempt to resolve them, they merely create more paradoxes to which the only solution is completely replaying the future fort, or in other words, deleting it.

[Cruxador]

The thing we are picky about is that we want to have timetravel affect our game, that if someone else changes time that this change translates to a change for us the player.

But the only possible change there would be easy to implement - suddenly there's a new god, who says he's from the future. Of course, this shouldn't happen often. Perhaps once every five pantheons, tops.

Paradox and things are irrelevant - history is remade each time. If you journey to the past, you lose the present.

Even with a new branch in the timeline you have the special "meet yourself" problem . For example if the change in the past (like a change on a another continent) of a altered timeline wouldnt change anything in your parallel existence to the point where you meet yourself. It would just be akward how the player double acts etc. and you would need a good number of informations to reconstruct the players state at a given time.
[/quote]There are two possibilities here: You don't encounter yourself, for whatever reason, or you encounter an NPC with your name. Which one is appropriate depends on how history-integrated player controlled gods are.

The problem is not self paradoxes: those can be removed with a small wave of the hand. It is the problem of the king's son's son's daughter being the 4th migrant of wave #2 in your fort in the future. And say she is your only mason, who was solely responsible for building both most of your furniture and the blocks for the walls of your entire aboveground fortress. There is no way to just wave that away without it resulting in making either fort mode or the time travel itself pointless.
Or another example: kill off the goblins in the past who in the future came and killed 10 of your fort of 30. Even compensating by resurecting the originally dead dwarfs, it will cause problems in things as mundane as the food and ale supply. No matter how your compensate, it will result in paradoxes which if a magic wand is waved over them in an attempt to resolve them, they merely create more paradoxes to which the only solution is completely replaying the future fort, or in other words, deleting it.

You cannot have two games active on the same world at once. You can be playing either God OR Fortress. Ergo, no problem.

[Dakk]

Currently its technicaly impossible to do realistic timetravel

realistic timetravel

realistic timetravel

Some sort of time travel IS possible, throught time dilatation, which has been proven to be a real phenomena. When you travel at very high speeds for a very long period of time, like the astronauts living for a whole year on board of a space station, time goes a bit slower to your then it does to everything else, so if you stay in space moving at about 300 kilometers per second for about a year, you

[darius]

realistic timetravel

What about wormhole time travel? As far as i remember it allows (theoretically) to travel back in time but not before wormhole was constructed.

[Draco18s]

How has no one mentioned Achron yet?

[Soralin]

The self-paradox can be avoided Quantum Leap style. You become yourself at any given point in time, so you can't meet yourself. What's different is now you have foresight.

That's called loading an old saved game.

How has no one mentioned Achron yet?

I agree, it should be added, so I went back and put it there yesterday.

[orbcontrolled]

tl;dr: Travel to any day in history. Only 546 gigabytes for a 200 year old world.

I think time travel in DF is plausible, and would also be useful, even if paradoxless-time travel is basically just an advanced form of savescumming. I personally find savescumming immensely useful, and it wouldn't even be cheating if you were a demi-god or whatever. Time travel would be even better because your character would retain all his attributes/items from the previous timeline.
The possibilities become even greater if you could carry a whole fortress (or at least a small sphere of tiles) into the past/future with you.
Imagine the very first elven settlement in the world being crushed out of existence as a mature fortress materializes around it. Alternatively, imagine your entire fortress exploding with the force of an A-bomb because you accidentally materialized it on top of some elves.

Technology-wise, all you need for that kind of time traveling is frequent save states. Choose one, and the game makes a copy of your character/fort, restores the state, and inserts your character/fort back into it (ability to go back to original timeline: optional depending how much hard drive space you're willing to give it).
All that we need to travel into the future is the ability to give the world back to worldgen for a period of time.


Just for fun, I did some (very very) quick-and-naive calculations of what it would take to be able to savescum to (almost) any point in your world history.

My current one-fortress save file (I think its a medium world, not sure) is 7.48 MB.
I'll assume each save would be roughly that big. We could reduce the amount with compression, and a bunch of other tricks, but I can't begin to imagine how that would affect the numbers, so for now, each save is 7.48MB.

Lets say the game makes a backup of the state of the world at the beginning of every day (whether you are in fortress mode, adventure mode, or world gen, it doesn't matter), for a 200 year old world that works out to 73000 days, and 546GB.
The estimate could also be much lower if the game only starts saving states after the player first takes control, before that you can just tell world gen to stop at x amount of days.

I think 546GB is actually not too bad. Terabyte drives are only $100-$200 at staples.

With some optimization you could probably get the game to save without lag by streaming the data to disk as the day proceeds, or saving the previous day to disk while the current day happens. Adventure mode would be a lot easier than fortress mode since days are so much longer, and worldgen doesn't need to save it's state much at all since it can just re-run itself starting from a state.


And there you have it. DF time travel for the cost of just a few hundred gigabytes.


Also:
Imagine being able to give those saved states to something like VisualFortress, and make a stop-motion movie of your fort being built, or the world evolving!

[Cruxador]

tl;dr: Travel to any day in history. Only 546 gigabytes for a 200 year old world.

[omitted for brevity]

First of all, nobody's suggesting the ability to uproot sites from their position in time. That's a bad idea, and is functionally impossible. Supposing, however, that this was somehow made possible, there would still be no need to replicate the save daily. That merely leaves us with fortresses following the same rules as individual creatures, specifically, gods.
Luckily for this situation, all necessary data exists within the history files. Thus your save would be 7.48MB.

[darius]

And it really could be done. E.g using similar tech to "time machine"(tm)(r)(apple) which basically has all the data in you computer at any given save point. Save points are distributed like this:

Time Machine saves the hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for everything older than a month.

What would be hard is logics of time travel: e.g elf genocide in past => fort now has no elf totems. This could be solved in number of different ways:
1. no totems at all. (including profit lost, items no bought etc)
 implications: if no item is present so it would leave random empty places. This could be intentionally left as it is (needing you to go back and fix problems) or could be solved by 2 (replace missing empty places with something)
2. replacement. (no elfs => more goblins=> goblin totems)
3. 1.+ smart ai. Probably the hardest. All fortress(or adv) activity would be replaced by AI which interprets your previous buildings, status as a suggestion. If they succeed fort is restored to normal (exact state) except elf totems missing. If they fail... Oh well you screwed with time
4. <no elf> totems. easiest way: replace all elf totems with <OMG TIMEERROR> totems and destroy when possible (simulating a time way crashing only present time.

I would probably go with 3 coz it's the most challenging and it solves numerous problems e.g. killed not only elves but goblins, kobolds and other dwarves in the past. Or killed all the dwarves. And so on.

[Osmosis Jones]

realistic timetravel

What about wormhole time travel? As far as i remember it allows (theoretically) to travel back in time but not before wormhole was constructed.

The problem is, wormholes aren't realistic. Outside of possible quantum froth behaviour (which is so small that if it was scaled up to the point where it would be of an observable size, an atom scaled by the same amount would be larger than the observable universe), wormholes are generally accepted as requiring either a type of matter that has no theoretical or observed reason to exist, crossing a literal point of no return (with the other end also being inside such an event horizon) or otherwise requiring manipulations of spacetime that beggar the imagination.