Like so many things in VFX, crowd simulation can be done to a good level by anyone inclined to learn it, but it also gets ultra specialised. There are artists who JUST do crowds, and software JUST made for them (called Massive - created for the armies in Lord of the Rings, way back when!).

But if you don't want to learn even more software, and you don't have $4000 handy for a Massive licence, this sheet should get you up and running with the basics! You can even export the end result and drop it straight into Blender/Unreal/wherever, if you want.

One Agent, Three Parts

Like real life, a crowd is a bunch of separate people lumped together. Not rocket science. In simulation, they're called “agents”, and they're made of three core components:

This is Agent Cooper (most Agents don't have names, but this one's a Twin Peaks fan). An Agent consists of 3 parts:

Asset. An agent is a basic, rigged model. This can be a few cubes, or a scan of a person - it depends on how close you get and how powerful your computer is.

Animation. It moves a selection of looping moves - either hand animated, or mocap driven. The bare minimum would be a walk, but normal “idle” loops are necessary (because not everyone wants to walk all the time). Variations help - repetition can become VERY obvious when there's a lot of people. Anything else will be dependent on your film - running and death animations would be essential for a battle, but probably of limited use in a romcom (if you DO use them in a romcom, PLEASE send me the film to watch).

Reason for living. Finally, each agent has a “brain”. The most basic brain just holds a destination and a bubble of personal space, like when you're commuting to work in the morning. More complex brains are necessary for more complex behaviour, but again that is going to be film specific.

Fight!

Battles are just crowds plus attack and death animations. A crowd artist on the original Lord of the Rings once told me that he'd accidentally made a bunch of the orcs too scared and they all started running away. Without time for re-simming, they just deleted the cowardly orcs. Lesson being - never overthink the simulation stage. You can't recreate human behaviour reliably, so instead study nature, get as close as you can, and fudge the rest.

When I shared this sheet with the Shoot First team, most of them instinctively made the odds uneven, and watched the losers die. I hope that you are better than that.

What’s Inside

•The Agent - Start with one basic rigged model.

•The Build - Give your model some looping moves, duplicate it, then vary the copies until nobody looks the same.

•Four Dials - Play with four simple attributes for very different crowds, from angry mob to chilled.

•Directing It - You can't order a crowd around, so learn to influence it with targets and barriers.

•Battle - The gloves come off - who are you rooting for?

•Swarm - Bugs and people aren't so different, so use the same rules to send a swarm looking for food.