Houdini 20.0 Crowd simulations

Specifying terrain for crowds

How to specify terrain geometry for agents to walk across.

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The crowd solver can have your agents stick to terrain geometry and perform foot placement on the terrain. Only one geometry object can be used as terrain with a crowd solver. If agents move off the terrain, they will snap to the ZX plane.

Set the terrain for a crowd simulation

  1. Select the geometry you want to use.

  2. On the Crowds shelf tab, select the Terrain tool.

    This turns on the terrain-following controls on the Terrain tab of the Crowd Solver node, and sets it to the selected geometry.

    You can limit the terrain-following behavior to certain groups by putting a space-separated list of group names in the Agent Group parameter on the Crowd Solver node.

    You can also adjust or turn off automatic foot placement.

Foot adaptation

The crowd solver can manipulate agent skeletons to automatically place agent feet in their proper positions as they walk along non-flat surfaces.

See also

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.