Abstract: We present a new model for diffuse material, i.e. water-air mixtures, that can be combined with particle-based fluids. Diffuse material is uniformly represented with particles which are classified into spray, foam and air bubbles. Physically motivated rules are employed to generate, advect and dissipate diffuse material. The approach is realized as a post-processing step which enables efficient processing and versatile handling. As interparticle forces and the influence of diffuse material onto the fluid are neglected, large numbers of diffuse particles are efficiently processed to realize highly detailed small-scale effects. The presented results show that our approach can significantly improve the visual realism of large-scale fluid simulations.