Real world physics, simulated human behavior, and realistic interaction. Discover how AI-based ‘intelligent’ crowds are pervading Hollywood blockbusters… and how you can create your own digital army.

Richard Attenborough’s 1982 film Gandhi currently holds the world record for the largest number of extras in one film: 300,000. You read that correctly… over a quarter of a million people showed up for Gandhi’s funeral procession scene. Only 1/3 of those extras were paid.

But that would likely never happen today. The talent would still be unpaid, but it wouldn’t really be ‘talent’ at all… just digitally rendered animations. The area of crowd dynamics and crowd simulation in VFX has exploded over the last few years – with the ability to virtually create groups of ‘agents’ with lifelike characteristics.  Agents can appear so lifelike, that the need to bring in actual extras is in many cases unnecessary.

In 2001, Peter Jackson’s Lord of the Rings was a jumping off point for the development and acceleration of VFX crowd simulation in feature films and movies. Similarly, the lines are now blurring between crowd dynamics technology being used in film and video games. Let’s look deeper into crowd simulation and dynamics, real-world examples, and how you can utilize this VFX technology in your own projects.

Basics of Crowd Simulation

There are two fundamental ways to create crowd simulations. You either a) attach the crowd’s movement, reaction, etc to ‘particles’ or b) give your crowd ‘artificial intelligence’.

As you may have correctly assumed, the first route is the simplest. Movement and behavior of your crowd would simply be ‘attached’ to a path generated by point particles. With this process it’s possible to simulate realistic physics, but the crowd would be unintelligent and interaction amongst the agents would be limited.

That’s why AI-based crowd dynamics takes it to the next level. When Peter Jackson needed to simulate armies for fight scenes in Lord of the Rings, it was imperative that these AI-based agents be able to interact with each other and influence each other’s actions. Wikipedia breaks it down well:

Entities are given artificial intelligence, which guides the entities based on one or more functions, such as sight, hearing, basic emotion, energy level, aggressiveness level, etc. Entities are given goals and then interact with each other just as members of a real crowd would. They are often programmed to respond to changes in their environment; for example, they may climb hills, jump over holes, scale ladders, etc.

Because an AI-based system is more realistic, it’s more difficult to program and more expensive to implement. Over the last few years however, some of these VFX tools have trickled down from behind the closed doors of high-end visual effects studios (like Jackson’s WETA) into the hands of the everyday designer.

Note, in many cases, VFX artists will shoot small crowds and duplicate/composite this footage to create a more ‘full’ crowd, however the behavior of these crowds would not be dynamic (directly editable).

Crowd Simulation Software

There are other crowd simulation apps for civil and pedestrian engineering, but for the purpose of this post we’re just highlighting the most popular software options for film and video.

Golaem Crowd

Golaem Crowd is an Autodesk Maya plugin that makes high-end crowd dynamics accessible. Highlights of the plugin include built-in behaviors for agents, real-life physics, universal diversity controller (easily modify props, behavior and shading for a more diverse crowd) and obstacle detection. You can take Golaem Crowd for a free 30 day trial (Windows only). Renting it for 3 months will set you back nearly $2,000, while a permanent license is $6,599 USD.

Massive

Massive seems to be the Hollywood leader when it comes to high-end crowd dynamics VFX. Developed during the production of Lord of the Rings (2001-2003), Massive went on to become a standalone licensed software package. The AI component of Massive is industry leading – “the software enables every agent to respond individually to its surroundings, including other agents”.

Since then, Massive has been used on other Hollywood features including Avatar, King Kong, 300, The Hobbit and World War Z. A Massive license for Maya is currently $3,500 USD.

Miarmy

Miarmy is another Maya based plugin that has been used in a wide variety of Hollywood features including Sherlock Holmes, Insurgent and Ant Man.  With a host of built-in presets, Miarmy can take much of the labor out of agent interaction. In fact, the video at the top of this post (the entertaining “I’ve Fallen and I Can’t Get Up!”) was created using Miarmy. It’s also the lowest price of the three, with a price tag of $2,600 USD per license.

Examples of Crowd Dynamics in Film/Video

Want more examples of beautifully crafted crowd dynamics? Check out the following videos by leaders in the visual effects industry.