How 'Lord of the Rings' Used AI to Change Big-Screen Battles Forever

An invading force, 10,000 strong, marches through a storm toward a fortress built into the side of a mountain. From a distance, the combatants look like ants -- menacing and alarmingly well organized. They rattle their spears and snarl through teeth that have never known modern dentistry, and when lightning strikes, it reveals their sheer numbers. Volleys of arrows fly, swords find their way to the weak spots around breast plates. Bodies on both sides hit the ground. This bloody affair is the Battle of Helm's Deep, from The Lord of the Rings: The Two Towers.