OptionalintensityOptionalparticlesParticles emitted by an average fall at intensity 1. Default 44 — density is what merges sprites into continuous haze, so this is the lever to reach for before per-particle alpha, which saturates to white.
OptionalmaxHard cap per fall, so a huge river doesn't blow the budget. Default 128.
Density multiplier; 0 emits nothing. Default 1.