Crowd Simulation
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!
One agent, three parts
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.
Take him for a walk
Agent Skating
Turn off stride matches speed and watch the feet. The agent can get slippy really quickly. This is something to be aware of in all looping animation - the figure is basically walking on the spot, and then moved around. The walk animation has to sync with the distance that they've travelled, otherwise they end up either frantically flapping their legs and making hardly any progress, or gliding around on concrete.
The order of work
- Build oneA body that reads at the size it will actually be on screen.
- Give it a few loopsIdle, walk, jog. Cycles that end where they started.
- Copy itScatter the copies across the ground you care about.
- Give them a wantA target, a barrier, a bubble of personal space.
- Break the samenessLarge changes to variety are easy to do and are what really make the difference. Just be aware that you need to go REALLY bold to properly break the feeling of sameness. Like with most creative things, if you go so far that it breaks, you can go JUST under that breaking point, and it'll work.
Angry Mob, Army, Chilled, Panic
4 simple attributes for very different results
Try these
Some presets to see how differently the crowd behaves just by playing with these 4 attributes
You can't make people do what you want by asking
Influence them instead
Tap the floor to move the target. The crowd re-plans instantly, because no one is following a path you drew.
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.
Stack the odds in favour of your favourite colour - when the other army has lost a third of their men, they'll break and be hunted down.
Different sizes, same brains
Bugs and people aren't so different when you're zoomed out. Both walking along the ground looking for something tasty to take back home.
In this case we've put some food on the ground. If you're feeling generous you can click on it and add some more. If the bugs are set to follow each other's trails, they'll find their own rhythm once a few of them have found the goods.
In terms of the technical setup, in VFX, it's all pretty much the same.