Houdini 20.5 Particles

Instancing and Rendering

On this page

Instance geometry on particles

To...Do this

Instance geometry on particles

  1. Select the particle system you want to be affected.

  2. Click the Instance Geometry on Particles shelf tool on the Particles tab.

  3. Select the object you want the particles to be replaced with and press Enter to confirm your selection.

For specific parameter help see the POP Instance DOP node help.

Rotate the instanced geometry using torque

  1. Insert a POP Torque DOP node into your chain.

    Torque is like sticking a handle on something and rotating it by pushing on the handle.

  2. Set the desired Axis to spin the particle around, and the Amount of speed.

Make the instanced geometry look at an object

  1. Insert a POP Look At DOP node into your chain.

  2. Set the Mode to Target is Point.

  3. Set the Reference Object for the particles to look at. 1The objects align in the direction of the reference object during the simulation.

    Note

    If no reference object is used, the particles will look at 0, 0, 0. You can modify the Target parameter to change its location.

Make the instanced geometry look at a plane

  1. Insert a POP Look At node into your chain.

  2. Set the Mode to Target is Direction.

  3. Set the Target parameter to where you want the particle to reorient to face. In the image below, Target is set to 0.5,0,1.

Rendering Instanced Geometry

When you create a particle system, Houdini also creates a renderable object at obj level. For example, if you create a particle system with the Location Particle Emitter shelf tool, your renderable object will be called location_particles.

  1. In order to render instanced geometry, append an Instance SOP after the DOP Import Fields SOP node inside the renderable object.

  2. On obj level, turn on the location_particles node’s blue Display/Render flag. If necessary, turn off other Display/Render flags to render only the instances.

Motion blur

When calculating motion blur, Mantra by default assumes the geometry of an object is unchanging, and blurs it as a whole. For a particle system obviously the points are moving, so you need to turn on velocity blur to use the velocity (v) attribute of the points to blur them individually.

To enable motion blur on particles you must enable it on the object as well the render node.

To...Do this

Enable velocity blur on an object

  1. Select the object containing the particles.

  2. In the parameter editor, click the Render tab, then the Sampling sub-tab. There, turn on Geometry velocity blur.

Enable motion blur on a render node

  1. In the main menu open Render ▸ Edit Render Node and choose the render node.

    If you don’t already have a render node, you can create one by choosing Render ▸ Create Render Node ▸ Mantra.

  2. In the parameter editor, click the Properties tab and then the Sampling sub-tab. There, turn on Allow motion blur.

Particles

Getting started

Behavior

Next Steps

Reference