Yunhe Pan

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.

Advanced design for a realistic virtual brush

This paper proposes a novel algorithmic framework for an advanced virtual brush to be used in interactive digitalpainting. The framework comprises the following components: a geometry model of the brush using a hierarchicalrepresentation that leads to substantial savings in every step of the painting process; fast online brush motionsimulation assisted by offline calibration that guarantees an accurate and stable simulation of the brushs dynamicbehavior; a new pigment model based on a diffusion process of random molecules that considers delicateand complex pigment behavior at dipping time as well as during painting; and a user‐adaptation component thatenables the system to cater for the personal painting habits of different users. A prototype system has been implementedbased on this framework. Compared with other virtual brushes, this new system is designed to presenta realistic brush in the sense that the system accurately and stably simulates the complex painting functionalityof a running brush, and therefore is capable of creating high‐quality digital paintings with minute aesthetic detailsthat can rival the real artwork. The advanced features also give rise to a high degree of expressiveness ofthe virtual brush that the user can comfortably manipulate. http://www.csis.hku.hk/songhuale‐brush/ providessupplementary materials for this paper.

Virtual hairy brush for painterly rendering

We propose a novel e-brush for calligraphy and painting, which meets all the criteria for a good e-brush. We use only four attributes to capture the essential features of the brush, and a suitably powerful modeling metaphor for its behavior. The e-brushs geometry, dynamic motions, and pigment changes are all dealt with in a single model. A single model simplifies the synchronization between the various system modules, thus giving rise to a more stable system, and lower costs. By a careful tradeoff between the complexity of the model and computation efficiency, more elaborate simulation of the e-brushs deformation and its recovery for interactive painterly rendering is made possible. We also propose a novel paper-ink model to complement the brushs model, and a machine intelligence module to empower the user to easily create beautiful calligraphy and painting. Despite the complexity of the modeling behind the scene, the high-level user interface has a simplistic and friendly design. The final results created by our e-brush can rival the real artwork.