A solid model based virtual hairy brush

We present the detailed modeling of the hairy brush used typically in Chinese calligraphy. The complex model, which includes also a model for the ink and the paper, covers the various stages of the brush going through a calligraphy process. The model relies on the concept of writing primitives, which are the smallest units of hair clusters, to reduce the load on the simulation. Each such primitive is constructed through the general sweeping operation in CAD and described by a NURBS surface. The writing primitives dynamically adjust themselves during the virtual writing process, leaving an imprint on the virtual paper as they move. The behavior of the brush is an aggregation of the behavior of all the writing primitives. A software system based on the model has been built and tested. Samples of imitation artwork from using the system were obtained and found to be nearly indistinguishable from the real artwork.