Houdini 17.0 Nodes Dynamics nodes

POP Steer Seek dynamics node

Applies force to agents/particles to move them toward a target position.

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

Tip

To make agents chase the nearest goal: Use the Attribute Transfer geometry node to set up attributes on the goal points that contain the particle ID of the closest agent. Then set Match method to "Point per particle" and set Goal ID to the attribute you created with Attribute Transfer.

Parameters

Activation

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

Group

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.

Output Attribute

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

This 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).

Weight

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

Goal

Attraction Type

Position

Enter a set of "goal" coordinates for agents to move toward.

Particles

Specify a group of dynamics particles. Agents will move toward particles in that group.

Points

Specify point geometry. Agents will move toward the those points.

Surface Points

Specify surface geometry and UVW coordinates on that surface for the agents to move toward.

Goal

When Attraction type is "Position", the 3D position agents should move toward.

Point Group

When Attraction type is "Particles", the name of a group of dynamics particles to use. Leave this blank to use all particles in the system.

SOP Path

When Attraction type is "Points", the path to an object or geometry node containing the point geometry (for example, /obj/bird_locations).

Point Group

When Attraction type is "Points", the name of a group of points within the geometry to use. Leave this blank to use all points.

Match Method

When Attraction type is "Particles" or "Points", whether agents should move toward individual points or the average location of all points.

Average position

Move agents toward the average position of all goal points. (You can also specify a number of clusters to get multiple goal "averages".)

Point per particle

Match up agents/particles with goal points based on the value of attributes on each. For example, if Particle ID is foo and Goal ID is bar, then agents/particles will follow whichever goal point has the same value in the bar attribute as the agent/particle has in the foo attribute.

Number of Clusters

When Match method is "Average position", group the goal points into this many clusters. Agents will move toward the centroid of the nearest cluster.

Particle ID

When Match method is "Point per particle", the name of the attribute on the agent/particle to match up with a goal.

Goal ID

When Match method is "Point per particle", the name of the attribute on the goal to match up with the agent/particle.

Force

Force Scale

How much force to apply toward the agent’s goal point.

Maximum Distance

Maximum distance (in meters) to look for goal.

Arrival

Stop the agents/particles once they are near the goal position.

Braking Distance

When Arrival is on, the distance (in meters) at which agents/particles start to slow down.

Braking Scale

When Arrival is on, how fast the agents/particles slow down once they reach their goal.

Pursuit

Agents/particles chase the goal by anticipating where it will be.

Prediction Factor

When Pursuit is on, how many time steps to look ahead when predicting the course of the goal.

Examples

The following examples include this node.

Formation Crowd Example Example for Crowd Solver dynamics node

Crowd example showing a changing formation setup

The setup creates an army of agents. There are two paths created. Middle part of the army starts moving and then splits into two formations. One goes to the left, the other groups keeps marching forward and slowly changes formation to a wedge shape.

To keep the agents in formation a custom geo shape is used. It’s points are used as goals for indiviudal agents. Using blendshapes the shape can change allowing for different formation changes. Dive inside the crowdsource object to see the construction.

Note

The animation clips need to be baked out before playing the scene. This should happen automatically if example is created from Crowds shelf. Otherwise save scene file to a location of your choice and click Render on '/obj/bake_cycles' ropnet to write out the files. The default path for the files is ${HIP}/agents.

Street Crowd Example Example for Crowd Solver dynamics node

Crowd example showing a street setup with two agent groups

The setup creates two groups of agents. The yellow agents are zombies which follow a path of the street. The blue agents are living pedestrians that wander around until they come into proximity of the zombies and then they swtich into a running state.

Triggers to change agent states are setup in the crowd_sim dopnet. The zombies group uses proximity to the stoplights and the color of the light to transition into a standing state when lights are red. The living group transition into a running state when they get close to the zombie agents.

Note

The animation clips need to be baked out before playing the scene. This should happen automatically if example is created from Crowds shelf. Otherwise save scene file to a location of your choice and click Render on '/obj/bake_cycles' ropnet to write out the files. The default path for the files is ${HIP}/agents.

See also

Dynamics nodes