Houdini 16.5 Nodes Particle nodes


Contains a VOP network that can manipulate particle attributes.

On this page

This node contains a VOP network (double-click the node in the network editor to go inside it) which can use POP context VOPs to to manipulate attributes on particles. (To define a SOP using a (textual) VEX program instead of a VOP network, use the VEX POP instead.)


If there are no particles, the network will not run.


This node is useful for creating "one-off" programs to manipulate particles in a single particle network. To use a VOP network to define a reusable particle node type, see creating a VEX particle node type.



When this parameter is non-zero, the VOP network inside is run on the incoming particles. This parameter allows you to keyframe application of the contained VOP network on and off.

Cache incoming geometry

Makes a copy of the incoming particle geometry before running the contained VOP network on it so VOPs that query attributes on the input geometry are guaranteed to get the original incoming values.

When this option is off, the node runs faster, but since the contained VOP network modifies the input geometry as it goes, it’s possible that some VOPs will get the modified value (if the particle has already been affected) rather than the original incoming values.

Source group

If you enter the name of a point group in the first input geometry in this parameter, only the points in that group will be affected by the VOP network.

Number of threads

The number of separate threads to use to evaluate the points. The default is no threading.

Since Houdini evaluates the VOP network for each particle in the input geometry, it can benefit greatly from threading on a multi-processor or multi-core machine.


The following examples include this node.

PopFlow Example for Particle Fluid Solver dynamics node

This example demonstrates how to integrate a POP network with a particle fluid simulation, granting one the Total Artistic Control of POPs with the fluid dynamics of the particle fluid simulator.

ParticleVolumeCollision Example for Volume Sample VOP node

This example demonstrates how to set attributes on a particle based on the value of a volume at the particle’s position.

To accomplish this, you can use a VOP POP to edit the particles, using the Volume Sample from File VOP to sample the volume.

In the example, particles are colored differently based on whether they are "in" or "out" of the volume, where "in" is defined in the example as "the value in the volume is > 0 at the position of the particle", but could easily be changed.

See also

Particle nodes