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. It was one of the first cinematic battles powered by Massive, a piece of software designed specifically for Lord of the Rings to create computer-generated armies using artificial intelligence to simulate realistic battles on a tremendous scale.  

As movies like Star Wars have revolutionized special effects and studios like Pixar shaped the use of computers in cinema, Massive, first built by Stephen Regelous for the world-renowned, award-winning visual effect studio Weta Digital, helped elevate what audiences now expect from onscreen battles.