The AI Systems of Left 4 Dead

https://cdn.fastly.steamstatic.com/apps/valve/2009/ai_systems_of_l4d_mike_booth.pdf

Slides hosted by Valve; venue from the AAAI AIIDE 2009 speaker list. AI Director adaptive pacing: per-survivor emotional intensity rises with damage, incapacitation, and nearby kills and decays when not engaged; phases Build Up, Sustain Peak (3-5 s), Peak Fade, Relax (30-45 s); mobs every 90-180 s on Normal; boss events (Tank, Witch, nothing) shuffled along the route.

Storyteller director