Page 242 - Socially Intelligent Agents Creating Relationships with Computers and Robots

Towards Integrating Plot and Character 225

Major value changes occur in each scene. Each scene is a large-scale story
event, such as "Grace confesses her fears to the player". Scenes are composed
of beats, the smallest unit of value change. Roughly, a beat consists of one
or more action/reaction pairs between characters. Generally speaking, in the
interest of maintaining economy and intensity, a beat should not last longer than
a few actions or lines of dialog.

4.1 Scenes and Beats as Architectural Entities

Given that the drama manager’s primary goal is to make sure that activity in
the story world is dramatic action, and thus turns values, it makes sense to have
the drama manager use scenes and beats as architectural entities.
In computational terms, a scene consists of preconditions, a description of
the value(s) intended to be changed by the scene (e.g. love between Grace and
the player moves from low to high), a (potentially large) collection of beats
with which to construct the scene, and a description of the arc that the value(s)
changed by the scene should follow within the scene. To decide which scene to
attempt to make happen next, the drama manager examines the list of unused
scenes and chooses the one that has a satisfied precondition and whose value
change best matches the shape of the global plot arc.
Once a scene has been selected, the drama manager tries to make the scene
play out by selecting beats that change values appropriately. A beat consists
of preconditions, a description of the values changed by the beat, success and
failure conditions, and a joint plan to coordinate the characters in order to carry
out the specific beat.

4.2 The Function of Beats

Beats serve several functions within the architecture. First, beats are the
smallest unit of dramatic value change. They are the fundamental building
blocks of the interactive story. Second, beats are the fundamental unit of char-
acter guidance. The beat defines the granularity of plot/character interaction.
Finally, the beat is the fundamental unit of player interaction. The beat is
the smallest granularity at which the player can engage in meaningful (having
meaning for the story) interaction.

4.3 Polymorphic Beats

The player’s activity within a beat will often determine exactly which values
are changed by a beat and by how much. For example, imagine that Trip
becomes uncomfortable with the current conversation - perhaps at this moment
in the story Grace is beginning to reveal problems in their relationship – and he
tries to change the topic, perhaps by offering to get the player another drink. The
combination of Grace’s line of dialog (revealing a problem in their relationship),