Houdini 20.0 Crowd simulations

Crowd obstacles

How to set up obstacles for agents to avoid.

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You can specify static DOP objects for agents to avoid using a behavior. You can put this behavior before the behavior merge node.

Setting up static DOP objects as obstacles

  1. Make the obstacle object a static object in the crowd simulation.

  2. Select the obstacle object. On the Crowds shelf tab, click Obstacle.

The shelf tool creates a POP Steer Obstacle node, sets it to avoid the static object, and wires it after the merge_states node.

Because the POP Steer Obstacle is after the merge_states node, it applies to all agents regardless of state. To make agents avoid an obstacle only in one state, move the POP Steer Obstacle node between the State node and the merge_states node. See crowd simulation network and states and behaviors for more information.


Collisions and avoidance are calculated using the geometry bound to the character skeleton.

Crowd simulations

Getting started

  • Basics

    An overview of Houdini crowd simulation concepts.

  • Setup

    How to set up and edit a crowd simulation.

The moving parts

  • Agents

    About agents, the moving actors that make up a crowd simulation.

  • States

    About agent states, the virtual mood of each agent that controls the agent’s animation and the behaviors it runs.

  • Triggers

    How to specify conditions that cause agents to change from one state to another.

  • Caches

    Tips for efficiently caching and loading crowd sims.

SOP crowds



  • Diversity

    How to create a more realistic crowd by making agents look and act differently.

  • Attaching cloth

    You can add and constrain vellum cloth as part of agent shape geometry, and then simulate the cloth based on agent movements.


  • Foot planting

    How to set up agents to adapt their animation to terrain and prevent skating.

  • Terrain

    How to specify terrain geometry for agents to walk across.

  • Obstacles

    How to set up obstacles for agents to avoid.