Abstract: This paper presents a physically-based method for simulating ink dispersion in absorbent paper for art creation purposes. We devise a novel fluid flow model based on the lattice Boltzmann equation suitable for simulating percolation in disordered media, like paper, in real time. Our model combines the simulations of spontaneous shape evolution and porous media flow under a unified framework. We also couple our physics simulation with simple implicit modeling and image-based methods to render high quality output. We demonstrate the effectiveness of our techniques in a digital paint system and achieve various realistic effects of ink dispersion, including complex flow patterns observed in real artwork, and other special effects.