The OctaneRender® for Houdini® plugin can render large amounts of particles using the native Octane Sphere Primitive.
Figure 1: Houdini particles rendered with OctaneRender
The plugin can use any kind of Object primitive as a particle's source, rendering the points as Octane spheres. You can enable the particle's feature in the Octane ObjParms - Particles tab. In this tab, you can also set the default radius for the particles without the Pscale attribute and the Radius Global Scale multiplier (Figure 2).
The particles support the P, Pscale, UV, and V point attributes. If the V attribute is available, OctaneRender can render the particles with motion blur if this feature is enabled in the ROP node.
Figure 2: Particle parameters found in the Particles tab
The particles feature has an option to pack the particle UV map, which is the information needed to map a color (usually Cd) and alpha attributes across the particles.