Abstract: This paper presents an effective method that simulates the ink diffusion process with visual plausible effects and real-time performance. Our algorithm updates the dynamic ink volume with a hybrid grid-particle representation: the fluid velocity field is calculated with a low-resolution grid structure, while the highly detailed ink effects are controlled and visualized with the particles. We propose an improved ink rendering method with particle sprites and motion blur techniques. The simulation and the rendering processes are efficiently implemented on graphics hardware for interactive frame rates. Compared to traditional simulation methods that treat water and ink as two mixable fluids, our method is simple but effective: it captures various ink effects such as pinned boundary [Chu and Tai 2005] and filament pattern [Shiny et al. 2010] with real-time performance; it allows easy interaction with the artists; it includes basic solid-fluid interaction. We believe that our method is attractive for industrial animation and art design.