Houdini 20.0 Nodes Dynamics nodes

POP Steer Obstacle 2.0 dynamics node

Applies force to agents/particles to avoid potential collisions with static objects.

Since 14.5

This is a crowd behavior node, but you can also use it on regular particles (see the Output attribute parameter).

This node sends out a certain number of rays in a cone along its forward direction, and tries to avoid collisions based on the closest ray hit. It looks for the optimal path based on the least obstructed ray, and uses environment normal directions as the braking direction.

See crowd obstacles for how to set up obstacles using shelf tools.



When this is off, the node will have no effect. You can animate this to turn the behavior on or off at different times.


Only modify a certain group or groups out of all agents/particles. You can name groups of agents using the Group Name parameter on the Crowd Source geometry node.


If turned on, shows the guide geometry for this node.


Even if the guide geometry is turned on here, it can be turned off by using the Hidden flag on the DOP node.

Output Attribute

If you are working with agents, set this parameter to Crowds steerforce. If you are working with particles, set this parameter to POP force.

Controls whether the node modifies the agent’s steerforce attribute (used by the crowd solver) or the particle’s force attribute (used by the POP solver).


Available when Output Attribute is set to Crowd steerforce. This number is used by the crowd solver to normalize and scale multiple forces that apply to an agent.


Whether to get the obstacle geometry from a geometry (SOP) node, or a piece of simulation (DOP) data.

SOP Path

When Source is “SOP”, the path to an object (for example /obj/house) or geometry node (for example, /obj/house/walls) containing the obstacle geometry.

Obstacle DOP Data

When Source is “DOP Data”, the name of a piece of geometry data, such as created by a Static Object DOP.

Collision Padding

Increases the effective size of the object. This can be used to control how close to the geometry agents can be.

Particle Scale Multiplier

The node uses pscale as the size of each agent/particle when calculating potential collisions. You can use this parameter to scale the value of pscale in the calculation, allowing agents/particles to be more or less tightly packed. This parameter can be overridden by a pscalemultiplier point attribute.

Far Avoidance Force

Amount of force applied to alter agent path to avoid the obstacle. This force follows a linear model and is useful for long range anticipatory avoidance. This can be mixed with a Near Avoidance Force.

Near Avoidance Force

Amount of force applied to alter agent path to avoid the obstacle. This force follows a non-linear model which produces better results for short range anticipatory avoidance and for dense crowds. This can be mixed with a Far Avoidance Force.

Front Search Distance

The maximum distance (in meters) in front of the agent to look for collisions with the obstacle geometry.


Number of rays to send out looking for possible collisions. The more rays you send, the earlier and more accurate the avoidance will be, but the slower the node will operate.

Samples Seed

Seed for the random number generator used to generate sample rays.

Sample Weight Bias

Bias for longer ray samples to have more influence.

FOV Horizontal

Field of view (in degrees) in the horizontal direction.

FOV Vertical

Field of view (in degrees) in the vertical direction.

Terrain Projection

Option for whether to project the obstacle avoidance force onto a terrain.

See also

Dynamics nodes