The Low-Tech AI of Elden Ring

8 hours ago

FROMSOFT's AI system in Elden Ring uses a low-tech but effective approach based on Havok Script (Lua).
AI decision-making is organized around 'Goals', which are states that can be stacked, turning the system into a Pushdown Automaton (PDA).
Goals are updated each frame and can push sub-goals onto the stack, with outcomes like Continue, Success, or Failure determining stack changes.
The 'activate' callback in Goals handles AI logic, often using weighted random selection to choose actions based on context and randomness.
Interrupts allow Goals to respond immediately to external events, such as damage or special effects, by modifying the goal stack.
Goals have timeouts to prevent stuck states and access actor data via an array of floats, avoiding complex systems like blackboards.
Actions are animation-driven, with animations carrying hitbox info, effects, and combo features, leveraging Havok middleware.
The system separates 'logic' and 'battle' scripts, allowing for reusable logic and bespoke battle behaviors.
Compared to Behavior Trees or planners, the pushdown automaton is faster and more flexible, avoiding state explosion.
The approach prioritizes designer and animator control, making it legible and effective for Soulsborne NPC and boss encounters.

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