Oz Project

Posted by Michael on May 25th, 2006, in Projects

http://www.cs.cmu.edu/afs/cs.cmu.edu/project/oz/web/papers.html

These are my remarks on An Oz-Centric Review of Interactive Drama and Believable Agents by Michael Mateas which offers an overview of the project’s goals (1997).

Oz is a reserach project into believable agents and interactive drama. Like Drama Princess, the Oz project focuses on drama much more than scientific AI. Unlike our work at Tale of Tales, the Oz project values plot and story arc greatly. This leads them to build a piece of software called drama manager, which we consider to be a deus ex machina for plot-fetishists.
We believe that the plot belongs to lineair formats. Non-linear formats should not be structured along plot arcs. This is no different now, with interactive media, as it has been in the past, when architecture, sculpture and painting were also completely plotless narrative formats.

Interestingly, they also mention the problem that I refered to earlier as the Seduction of Realism: When attempting to marry a technical field like Computer Science with a cultural activity such as story telling, it is extremely easy to become sidetracked from the artistic goals and to begin pursuing purely technical research. (Michael Mateas)

From the same text, we learn about the “requirements for believability” in characters:

• Personality – Rich personality should infuse everything that a character does, from the way they talk and move to the way they think. What makes characters interesting are their unique ways doing things. Personality is about the unique and specific, not the general.
• Emotion – Characters exhibit their own emotions and respond to the emotions of others in personality-specific ways.
• Self-motivation – Characters don’t just react to the activity of others. They have their own internal drives and desires which they pursue whether or not others are interacting with them.
• Change – Characters grow and change with time, in a manner consistent with their personality.
• Social relationships – Characters engage in detailed interactions with others in a manner consistent with their relationship. In turn, these relationships change as a result of the interaction.
• Illusion of life – This is a collection of requirements such as: pursuing multiple, simultaneous goals and actions, having broad capabilities (e.g. movement, perception, memory, language), and reacting quickly to stimuli in the environment. Traditional character artists do not mention these requirement explicitly, because they often get them for free (from a human actor, or as a deep assumption in animation). But builders of interactive characters must concern themselves explicitly with building agent architectures that support these requirements.

While this list is very useful, it bothers me that it is still written from the assumption that the actor performing the character actually feels the emotions, drives and desires. While it would be more correct, in my opinion, to claim that the character only needs to show symptoms that can be read as if it would posses these traits.

About the difference between realism and believability:

When watching a play or film, viewers know that the characters are not “real” but that does not detract from being engaged by the character.

Oz’s Drama Manager serves the purpose of creating plot in an interactive story. To be able to do this, the Drama Manager needs certain rules, an “evaluation function”. To author this system, Michael Mateas suggests the following steps:

1. write some linear (non-interactive) story as a sequence of “important moments”
2. reverse-engineer your own thinking to figure out why you think that particular sequence is a “good” story
3. capture this aesthetic as a set of features (over sequences) in an evaluation function
4. make sure that you have (approximately) captured your aesthetic by comparing the output of the evaluation function with your own evaluation of a set of sequences (of course include the original story – the one your “really” want to tell)

I find this highly problematic. First I don’t like the typical scientific way of taking a whole, breaking it apart and then trying to put it back together. I believe that you lose the essence of the whole when you work like that. Second, not unrelated, never, in these steps, is the user mentioned. It’s all about the author and what she wants and never about what you want the user to experience, let alone how.

He then continues to describe how this Drama Manager would, at each plot point, evaluate all possible future interactions to then choose one that is rated high by the evaluation function and push the story in that direction. Not only does this strike me as a million times more difficult than creating a believable agent, I also have serious doubts about the desirability of such a system. Ultimately the best you could achieve is a formulaic story. Because you literally apply a formula to a narrative. And formulaic stories happen to be the worst that film and literature have to offer.
Does this mean that it is impossible to make narrative art with interactive media? No. It just means that interactive media are not suitable for writing novels or creating movies, much like novels and movies are not suitable for painting pictures or carving marble.

4 Comments »