– The greater the “Scale Randomness” value, the greater the variation of the radius of the particles.
– Scale Randomness = 0 means no variation, all particles have the same radius.
– Scale Randomness = 1 means maximum of variation: radius assigned to the particles can vary from 0 to the value you set in Scale.
– In this example you can see how particles with differen radius (randomly assigned) interact with the plane (set as deflector). Remember: all particles seem to have the same size but it’s only because the radius is not visualized!
– Note: at this moment, with Blender 2.8 Beta git.80ffa73b3f87 I cannot render the Halo material, so I rendered this video using Blender 2.79b