The ink diffusion on Xuan paper is essentially a particle diffusion process, and the diffusion result is mainly
determined by paper structure and ink attributes. This paper introduces weighting fiber structure to model the Xuan paper,
which regards the paper fiber as the hindrance to ink diffusion. Based on the paper model, we present a novel simulation
method of ink diffusion using the diffusion equation with variable coefficient. The diffusion coefficient consists of
several factors including the fiber’s weights and the ink quantity in the current diffusion location. To efficiently solve the
ink diffusion equation, we also propose a new implicit difference method with high accuracy and linear time complexity.
Compared with the previous similar methods, our method is able to describe the spontaneous gray evolution and generate
a more natural diffusion boundary. The experimental results demonstrate that our approach can realistically simulate
different diffusion effects on different kinds of Xuan paper.