Multiple Agent Simulation System in Virtual Environment: MASSIVE. The Massive software was first developed in New Zealand by Stephen Regelous, primarily for the large-scale battle scenes in The Lord of the Rings. It was a huge stepping stone in filmmaking to be able to animate and control such large crowds. Through the use of fuzzy logic, Massive has the ability to allow individual characters (”agents”) to react to their independent environments while maintaining realistic motion without the need to animate each and every agent. 

Originating with UC Berkley professor Lotfi Zadeh, fuzzy logic is appropriately named. In fuzzy logic, not only can something be true and false, but can be true or false by varying degrees. The line between the true and false (or any set, for that matter) that is so prevalent in predicate logic is blurred. But this does not necessarily mean that the analysis is any less precise. Almost the opposite; fuzzy logic more closely resembles real life than does predicate logic. A simple logic set could consist of values “good” and “bad”. In defining a human, predicate logic would demand a value of either “good” or “bad”. But that just doesn’t happen in real life. A person can have good and bad qualities, which would alter their overall definition of either “good” or “bad”, and cannot carry only one label or the other. Fuzzy logic would allow a human to carry a proportion of each label. This same concept is applied to the Massive AI software, though on a much larger scale. In the case of a battle, some factors affecting a character’s actions would include: sight, hearing, proximity to others (comrades or opponents), basic emotion, energy level, aggressiveness, etc. In the agent’s effort to accomplish a given goal, these factors would impact their reaction, which would in turn alter the factors. If you have ever seen I, Robot, The Golden Compass, Happy Feet or many others., you can be thankful for Massive and the fuzzy logic that backs it. And the next time you see a large and intense battle scene, be aware that not all the characters are just acting, but making active decisions.

 http://en.wikipedia.org/wiki/Fuzzy_logic

http://www.massivesoftware.com/