Houdini 20.0 Particles

Following a leader or leaders

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Making particles follow leader particles can be set up using a POP Attract DOP node.

Making particles follow other particles

The screenshot below shows the DOP network to make particles follow other particles. The centerpiece is a POP Attract DOP node, added to the followers stream of particles.

  1. Set the Attraction Type to Particles.

  2. Next, open the Goal tab. In the Point Group, type the particle stream you want them to follow (stream name of the leader particles). In the following example, this is stream_leaders.

  3. To make the attractor work correctly, it’s mandatory to turn off Goal ID.

In the Force tab you can then set the Force Method to either Accelerate or Follow. If you choose Accelerate, a general force is applied in the direction of the leader particles. If you choose Follow, the velocity of the next frame is used and the speed is set to match the leader’s.


You may get better results by turning on Predict Intercept when using Follow. This will prevent particles from charging towards the moving particles and potentially overshooting them. Instead, the follower particles will anticipate the leaders' direction on the next frame, and try to head them off.

Changing the way followers behave

Another important parameter to consider is Match Method. This will change the way the follower particles behave. In the following example, there are 5 leaders. Setting Match Method to Average Position will take the average position of the 5 leaders to create a target. To create leader particles, select the leaders POP Location DOP.

  1. For Impulse Activation, enter $F==1. This expression sources particles only at frame 1.

  2. Set Impulse Count to 5. Change this value if you need more or less leaders.

  3. Additionally, change Const. Activation to 0 to disable constant emission.

If Match Method is set to Point Per Particle, the followers will separate into trails, with one fifth of the followers following each individual particle.

To create a more swarm-like effect, add a POP Force DOP with some noise in your followers stream.

Make particles follow an object

You can make particles follow an animated object the same way, by setting the Attraction Type to Surface Points and the SOP Path to your geometry object.


Getting started


Next Steps