Plazanearly four hundred people cross a plaza in low evening sun, each heading somewhere and stepping around the othersBattletwo armies charge and pair off to fightFishtuna scatter as two big hunters cut through
a bus turns through a junction at dusk while people cross at the lights and vans wait their turn
01 · Traffic
Run a town at rush hour
Cars wait at the red lights while people cross in front of them, and buses pull in at their stops. Edit a street curve and the town rebuilds around it.
Draw the streets as curves, then pick them and choose Simulate > Street traffic.
The curves become roads with sidewalks and crosswalks, with lights on the junctions.
Add a stops node and click the bus stops onto the roads with the Target tool. Then set how often the bus runs and how long it waits at a stop.
Press Play and the traffic starts. Turn on curb parking and cars pull in and out.
two armies charge across a field, pair off to fight and fall
06 · Physics
Fight a battle
Two armies charge across a field and pair off to fight. A light hit makes a soldier stagger, and a heavy blow drops a soldier as a ragdoll that stays where it falls.
Load the stock soldiers. They come with their own weapons.
Lay out an army on its own side of the field, and give it a team and its colors.
Draw the states: advance, charge when the other side is near, fight when it is in reach.
Set get up to never, so a soldier who falls as a ragdoll stays down.
Pick a ground and choose Simulate > Crowd. A Crowd node lands in the scene, and when you press Play people start walking. Then tell them where to go, and give them states when a goal is not enough.
Click targets and exits onto the ground in the view, and draw the paths you want walked.
In the Behavior editor, states are linked by arrows with plain conditions, such as when a horse reaches its goal or after 1 to 2 seconds in a state.
3DGeoCrowd
Direct agent sends one agent along a path you draw from this frame on, and the crowd still makes room for it.
After the sim, pick agents and recolor, retime or remove them without running it again.
3DGeoCrowdEdit
Write a move of your own in Python, or in WGSL that runs on the GPU, one thread per agent. The zombies hunt with a few lines of Python.
3DGeoCrowdChainPython3DGeoCrowdChainShader
the Behavior editor for riders and their horses: states linked by arrows that say when they are taken
the crowd tools on the Simulate menu, Direct agent among them, over a plaza where a hero's drawn path cuts through the walkers
the cafe terrace playing in the app, its crowd node on the canvas belowdots steered by a WGSL shader on the GPU
Everyday life
Give them things to do.
Put tables, benches or tills in the scene and people use them: they find a free seat, stay a while and leave. A schedule sends them where they need to be at the times you set.
Cafe terracefriends take a table together and sit down to talkShopshoppers browse the shelves and pay at the tillsStation squaretired commuters sit down on the benches
Friends arrive in small groups, and a group always shares one table.
3DGeoCrowdPlacedObjects
Shoppers browse the shelves, then line up and pay at whichever till is free.
Commuters carry an energy need. When it runs low they find a free bench, and they head for the platform when the train is called at 07:44.
3DGeoCrowdObjects
A schedule takes forty people through an office day: desks from 08:00, meetings at 11:00 and 15:00, home after 17:00.
3DGeoCrowdSchedule
Two or more agents can do things together, such as talk in a circle or walk side by side.
A timeline marker, an OSC message or a MIDI note can tell the crowd something happened, and it reacts: the birds scatter at a bang and the office empties at an alarm. Scrub back over a live show and the crowd replays what it heard.
An alarm marker sends an office to the nearest of three exits along a shared flow field, and where it gets too crowded the panic spreads. Scrub back before the marker and everyone is calm again.
Show control sends OSC, and the last part of the address is the event: /stage/drop arrives as drop. A tick on a trigger input works too, from MIDI or anything else.
OSCReceive
Wire a tracker in and real people join the crowd as live agents. Everyone keeps clear of them, and anyone close can stop to watch.
3DGeoCrowdFromTracking
Traffic lights come out as numbers, 0 red, 1 amber and 2 green, ready for lamps in the scene or a lighting desk.
3DGeoNavSignals
Footsteps come out as events you can turn into sound, and the head count and how crowded it gets come out as values.
the alarm rings and a busy office floor heads for the nearest exits, threading around the desks as the lights drop to red
How it works
One node runs the whole crowd.
Pick a preset and wire a ground, and the crowd comes out ready to render. When you want a step the Behavior editor cannot express, right-click it and choose Split into chain for the same crowd as a ready-wired chain of nodes.
a crowd on a plaza, from the quick start in the app's Help
What an agent does on every frame
01Think
The brain checks which state the agent is in and whether an arrow out of it is now true.
02Steer
The moves of that state push it toward where it wants to go.
03Keep apart
Avoidance makes room, so nobody walks through anybody else.
04Move
It turns and speeds up within its limits and keeps to its ground.
05Animate
Its character plays the clips that match its speed and state, feet planted.
06Draw
Near agents are drawn in full detail, far ones with less, down to dots.
The settings you will touch.
PresetCrowd
Start from a ready-made crowd, such as Walkers, Street, Flock or School.
CountCrowd
How many agents. Raise it while it plays and new agents are born on the frame you are on.
GoalCrowd
Wander, walk to targets, follow paths, follow lanes or head for the exits.
SpeedCrowd
The walking speed they prefer. Settings like this apply live from the current frame.
AvoidanceCrowd
Smooth for polite crowds, Look ahead for streams crossing, Push for a crush, None for people who stay in their seats.
GroundCrowd
Wire a mesh and the crowd works out where people can walk, up to the tallest step and the steepest slope you allow.
SeedCrowd
Same seed, same crowd. Change it for a different one.
Motion matchCrowd
Blend walk and run by speed, or let agents pick the best bit of any clip, for smoother starts and turns.
DrawCrowd
Characters for the render; boxes or points while you block out the shot.
Compute deviceCrowd
Application Default, GPU or CPU. Big crowds belong on the GPU.
Feet that stay planted.
A motion set measures a character's clips, so walks and runs follow speed and feet do not slide. Legs bend to slopes and stairs, and agents start at different points in their clips, so five hundred people do not step in time.
3DGeoCrowdMotionSet3DGeoCrowdAnimate
Far agents cost less.
Near the camera an agent is the full skinned character. Farther out it drops to a lighter mesh, then a few stored poses, then a flat picture that turns to face the camera, then a dot. Add billboards bakes those pictures from the viewport.
3DGeoCrowdDraw3DGeoCrowdImpostorBake
The same crowd as a chain.
Source makes the agents and the chain sim runs the frames. Behavior nodes push, the solver moves everyone, then Animate and Draw pose and draw them.
Bring your characters and your set in from another app. Send the crowd back out to your renderer, or keep it in the file that runs the show.
Comes in
Characters: glTF, FBX, USD, VRMGrounds and buildings as meshesStreets, rails and rivers as curvesTracked peopleTimeline markersOSCMIDIPython and WGSL moves
Goes out
USD: each character once, moved per agentAlembic meshes, frame by frameFBX: one take per agentCSV agent tracksIts own recording, to replay with no simFrames: EXR and PNG sequencesVideo
3DGeoCrowdExport3DGeoCrowdCache
Live
Projectors and second screensNDISyphon on a MacArt-Net and sACNEvents and values for sound and lights
