GDnD Wiki

GDnD Wiki

This site is for Ulster University students and staff. Enter the class access password to continue.

NPC Behaviour Readability

3 min read

Summary

NPC behaviour readability is the degree to which a player can understand what an NPC is doing, about to do, or trying to do. The aim is not perfect realism. The aim is legibility: players should be able to interpret motion, posture, timing, and contextual cues quickly enough to respond. In practice this makes behaviour design partly an animation problem, partly an AI-architecture problem, and partly a communication problem. (Carlisle, Game AI Pro 2, see source-game-ai-pro-2; Dyckhoff, Game AI Pro 360: Guide to Character Behavior, see source-game-ai-pro-360-character-behavior)

Key ideas

  • Intention over realism: Believable behaviour is behaviour that players can parse. Perfect physical realism is less important than clear signalling.
  • Movement model matters: Animation-driven motion, game-driven motion, and hybrids each trade precision for legibility in different ways.
  • Telegraphs need time: If an attack, search action, or callout happens too fast, the player reads it as unfair rather than intelligent.
  • Interruptions must stay coherent: Blending, cancelling, and redirecting actions should not destroy the apparent intention of the character.
  • Visibility is part of design: If the player cannot see the behaviour happen, much of the sophistication is effectively wasted.

In practice

Useful readability checks for NPC behaviour:

  1. Can the player tell what state the NPC is in?
  2. Can the player tell what changed?
  3. Can the player predict the likely next action?
  4. Does failure feel fair when the behaviour succeeds against the player?

Typical readability tools:

  • anticipation animations
  • barks or callouts
  • stronger pose silhouettes
  • context-sensitive facing direction
  • consistent use of cover, search, and patrol rhythms
  • selective slowing or exaggeration for key state changes

For Unity teams, this usually means coordinating:

  • Animator state timing
  • AI state or BT transitions
  • audio callout hooks
  • UI or VFX support where appropriate

Evidence

  • Carlisle frames behaviour realization as the problem of clearly communicating both action and intention so the player can read the character correctly. (Game AI Pro 2, see source-game-ai-pro-2)
  • Dyckhoff’s work on Ellie in The Last of Us shows the same principle from the opposite side: callouts only help if they are reliable enough that the player trusts them. A warning about an enemy the player cannot find damages perceived intelligence. (Game AI Pro 360: Guide to Character Behavior, see source-game-ai-pro-360-character-behavior)
  • The implication is that AI quality is filtered through player perception. A sophisticated internal model can still feel bad if its outputs are not legible.

Implications

  • Readability links npc-perception-systems, buddy-ai, combat-coordinator-pattern, and character-design.
  • Overly subtle behaviour often fails in practice because players read games under time pressure, not like film viewers with unlimited interpretation time.
  • Designers should evaluate NPC behaviour by asking “what did the player think happened?” as well as “what did the system do?”

Open questions

  • How much readability should come from animation versus explicit UI/audio signalling?
  • At what point does exaggeration become patronising or reduce the sense of a living world?
  • How should readability rules differ for stealth enemies, companions, and crowd/background NPCs?

npc-perception-systems · buddy-ai · combat-coordinator-pattern · character-design · game-feel · source-game-ai-pro-2

Graph View

Backlinks