Automated storytelling and interactive plot in games

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Original post by Balaam This a great collection of resources! Thanks for posting. I've recently implemented a very simple reusable plot framework and am interested in seeing how far I can take it.

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In an old post I said that the simplest possible plot consists of 3 objects: a PC who can take actions and has a motivation of wanting a goal, a 'goal object' (obtaining which is the climax of the plot) and an obstacle to keep the PC from just immediately obtaining the goal object. So in a sense you are choosing the conclusion (obtaining the goal object) and working backwards to create the starting game setup. You really do have to choose the 'victory condition' and work backwards to create the story. But that can work fine with interactivity. :) It's not obvious in this simplest possible setup, since interactivity comes from making choices, so let's make it a little more complex: the obstacle between the PC and the goal is an NPC guard. The player can choose whether to talk to the guard in an attempt to persuade him to give them the goal, or to punch the guard in the nose in an attempt to force him to give them the goal. So the player makes a decision and takes action, the NPC responds appropriately, and the game state has changed depending on the players action so that the next step toward reaching the goal is different. Maybe the guard can be persuaded, but not once he's been punched. Maybe the first punch just makes him mad, but the second one knocks him unconscious. So either way the PC eventually gets the goal object, but meanwhile the player has lived one of two totally different stories: one about persuasion, or one about violence. Voila, interactivity! [smile]

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Original post by sunandshadow This is the first time I've seen Trapper Zoid's thesis, so I'll comment on that first. :) I largely agree with this paper and the preferability of the plot-based system in the driver's seat, supported by good NPC and NPC interaction simulation. There are only two nits I'd like to pick: 1) The paper analogizes an interactive story as an equal conversation between actors and the audience in an interactive play. I think this is misleading - whether the story of a game is interactive or not there is a fundamental difference in the job of the game and the job of the player. A much more accurate way to imagine things is Neoshaman's analogy that the game functions as the DM or GM in a tabletop roleplaying game, while the player functions as a player. I believe that the job of the program is to create the world and establish the rules within which the player must struggle to accomplish goals, while the job of the player is NOT to create any of the world's content but instead to express opinions (by preferentially attempting to accomplish the goal by one of a variety of available actions) which in turn influences the game's selection of content to present to the player. So it's not by any means a conversation between equals.

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2) The problem with using a plot structure such as that of Propp, Polti, or Campbell, is not that they are too complicate, but that they are over-specified. The same problem exists to a lesser degree with the terms 'key' and 'door' - using such concrete terms prevernts people from realizing that any character action can function as a key, and obstacle can function as a door, and in a non-linear game each door ought to have several alternative keys. It's important to define the objects a story-generation engine would need to understand in as few classes, as generically, simply, and clearly as possible like a logical programming language so that the program can truly understand them and accurately manipulate them. What we want is the storytelling equivalent of a GUI toolkit such as QT or GTK, so the storytelling engine can select a class from the library and instantiate a specific unique version of it for a particular game session.

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Oh, one more thing: There may be only one overall goal in a game story, but in a game with levels, chapters, or episodes, each of these should have a subgoal. The subgoal essentially functions as an obstacle between sections of the game, with all the gameplay of the chapter adding up to unlock the door (and the door automatically locking once the player has passed through to control player progression, because the player should only ever be moving forward toward the climax, you lose dramatic tension and immersiveness if the player can go backwards.

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EDIT: It might also be desireable to provide more than one goal and have the player's choice of which goal to persue influence the game in the same way the player's choice of which method to use to persue the goal influences the game. But the more goals there were the less unity your plot would have, and items and objects relevant to one goal might be confusing red herrings to a player not persuing that goal.

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Original post by achilles_ Ah, interactive stories. My favourite topic of discussion. :) I always wonder why it is that people like to make the distinction between plot-led and character-led games. It strikes me that they really are both incomplete methods of interactive storytelling, neither really capable of accomplishing much without the other.

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You can see the results of story-based games everywhere. We get FPS-twitch games such as Half Life 2, which is really little more than a test of your reactions with a pretty slideshow story, and yet the industry heaps praise upon it as "advancing the state of the art". Advancing the state of the art for ATI and nVidia corporate accounts, maybe...

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Character-based games are a little harder to come by, because it's a lot harder to code a convincing facsimile of a human personality. (Although possibly not quite as hard as the appalling AI in Daikatana made it look!) Interestingly, some games developers have capitalised on this problem, and have done away with coding characters in favour of simply bringing real people together and letting them interact. Whilst the possibilities for inane gossip are almost infinite, the current state of character-based gaming leaves all essence of story to the players, providing nothing more than a series of mediocre public challenges with some half-baked excuse of a plot that every single player must work their way through. Even Everquest 2 and World of Warcraft can do little to disguise what is no more than a gruelling social experiment in repetition and toil.

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I've spent the last 6 months or so working on my own storytelling system. I was tempted down the story-based route at first, simply because it was so much easier to implement a rigidly-connected series of events than it was to develop a framework for social interaction with artifical entities. The route that I finally took is based more than a little on the discussions of interactive storytelling system in Crawford's book, and a lot of additional research into simplified natural language systems, I went down the route of creating the character framework first, and then introducing plot elements through agents. Agents can be characters (adding a murderer to a village full of people), or "fate" (for manipulation of intangibles, such as disease or luck). I give characters a routine, a base personality, a volatile memory, and a couple of motivations, and let them go off and do their thing. I then introduce appropriate agents for a story into the system, and then allow the player to start interacting. The player has exactly the same freedoms as any character in the system, and I allow them to form their own goals based on their experiences in the game. This way, whilst all the ingredients are in place for a story to evolve, I avaoid confining the player to any specified series of events, and shattering the illusion of freedom.

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So far, I've got a mostly-working prototype based on Agatha Christie's "Mousetrap", which has led to some rather interesting situations. It's obviously not as nuanced as the original, but it's recognisable as the same situation, and can lead to a number of reasonably convincing outcomes. (Though getting the murderer not to just shoot everyone immediately was an interesting exercise in tuning algorithms. :)

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I'm fascinated to find out what practical approaches others are taking, and especially how they see the field developing. For example, trying to actually specifically model a plot and develop (or implement) a grammar seems like a pretty intense method to provide the player with a limiting system for interaction. It seems to me that the act of implementing a plot structure that the player must adhere to is going to grossly limit the level of interaction allowed to the player. I like the idea of using an algorithmic approach to assembling a grammar of narrative into a dynamic story, and using that to direct events. It would certainly offer a great deal in terms of replay value. It would be interesting to see the result of synthesised story, I fear that it might feel slightly generic without the "art" that a human storyteller brings.

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Original post by Trapper Zoid I've seen the MMORPG approach as a 'solution' to the problem, but it's really just a way of deflecting it. It does nothing for the single-player RPG, and is reliant on everyone 'playing their part', which is not feasible for an open-to-the-public MMORPG. I guess you could model this with half a dozen human actors for every player, but that's not economically feasible.

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Original post by HAM ACtually I think you might be overlooking something. What could be very benificial to your goals would be to create a multiplayer game, were one of the key features of the game is story telling. Provide the players with mechanisisms to tell stories. This way you could concentrate on root mechanics and completely ignore AI. The AI is more than likely the biggest challenge. Seems to me what would be best is to have a very, very solid framework of mechanics and tools that the AI would use. Make a constrained tool set for telling stories. Let humans use it. Look at the results, modify the toolset. Repeat. During the course of this you will no doubt find mechanics that can be automated (a few steps closer to teh AI). And when you finally get something that is usable and workable, then try and tackle how the AI could mimic human choices made with that toolset. Dunno, Just one approach on research and developement.

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Original post by HAM Just curious. What games/systems have you made to tell stories? Have you ever created a simple story with branches and multiple endings?

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Have you ever written a choose your own adventure book?

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Seems the best approach would be to look at those systems you have previously made , and concretely isolate and describe thier short falls.

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I don't think this subject is any different than the other topics on these forums? You want to make a game? Don't start with a 3D MMORPG. Start with a text game first, then build up from there. You want to make automatic story system? Start with what is simple. I agree with you that the subject is difficult but possible. Like wise, there will be MANY ways to accomplish it. Starting with a base static system, and then attempting to add automation to it would seem to be a good approach.

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Original post by HAM Just curious. What games/systems have you made to tell stories? Have you ever created a simple story with branches and multiple endings? Have you ever written a choose your own adventure book? Seems the best approach would be to look at those systems you have previously made , and concretely isolate and describe thier short falls. I don't think this subject is any different than the other topics on these forums? You want to make a game? Don't start with a 3D MMORPG. Start with a text game first, then build up from there. You want to make automatic story system? Start with what is simple. I agree with you that the subject is difficult but possible. Like wise, there will be MANY ways to accomplish it. Starting with a base static system, and then attempting to add automation to it would seem to be a good approach.

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Original post by Vanquish Ok here are my favorite 2 links on this subject:

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Original post by sunandshadow I'd like to answer this too. [wink] I have indeed written a choose your own adventure book/simple branching game: I made one on paper way back when I was in 5th or 6th grade, and one with HyperCard a few years later, featuring a cadet entering a space academy and trying to start a romance with a fellow student. My current game design is _Xenallure: A Tapestry of Hearts_, which is a single player dating sim/RPG/adventure with a branching (but not at all automatically generated) multi-ending story.

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But studying these previous/current creations isn't terribly useful because it's an entirely different paradigm than a truly interactive game. It is much more useful to study what goes on in a writer's mind when they create a branching story, or a DM's mind when they run a tabletop roleplaying game. Like Trapper Zoid I learned in college that stories have a grammar just like language, and did a lot of research on plot structure. Being primarily a writer myself, I was interested in analyzing my own process of creating a story, since it seemed to me that if I can do it, and understand how I am doing it, I ought to be able to write a program which can do it too.

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It probably would be easiest to attempt to implement a story generation engine as an entirely text-based game first. The question is who's going to program it (since my programming skills are pathetic at best, I can describe how a story generation engine should work but I can't implement it myself). And how should it be implemented? A logical programming language (e.g. SOAR) database of specific game-objects which can be instantiated as part of each class? A standard searchable database (e.g. SQL) of all the properties of all the objects instantiated for a game session? What character creation and story type preference questions should we ask the player during the 'start new game' phase?

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Original post by Trapper Zoid The base of it was detailed character models like yours, except I also had hidden 'agents' that acted as overseers to the characters that dictates the plot elements. So you might have an agent that overserves the players actions to decide on the next plot point; as a loose example, if the player was busy stealing things, the agent would create and direct detectives to try and apprehend them. The idea was that the character were not fully autonomous but actors under the direction of higher controllers.

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Original post by Vanquish Not to interrupt, but some earlier posts caught my eye: "Agents can be characters (adding a murderer to a village full of people), or "fate" (for manipulation of intangibles, such as disease or luck). I give characters a routine, a base personality, a volatile memory, and a couple of motivations, and let them go off and do their thing. I then introduce appropriate agents for a story into the system, and then allow the player to start interacting. The player has exactly the same freedoms as any character in the system, and I allow them to form their own goals based on their experiences in the game. This way, whilst all the ingredients are in place for a story to evolve, I avaoid confining the player to any specified series of events, and shattering the illusion of freedom." That sounds amazing. Ive always thought that in an MMORPG setting what you really need is a civilization sim running (full city with npcs going about a schedule with needs) and maybe 25 special NPCs with a more detailed schedule and need structure, built for real interactivity.

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"So far, I've got a mostly-working prototype based on Agatha Christie's 'Mousetrap', which has led to some rather interesting situations. It's obviously not as nuanced as the original, but it's recognisable as the same situation, and can lead to a number of reasonably convincing outcomes. (Though getting the murderer not to just shoot everyone immediately was an interesting exercise in tuning algorithms. :)" Can I play? sounds great?