Various approaches for generating woodgrain patterns using computer graphics have been proposed so far. However, it is difficult to reproduce real woodgrain patterns using such conventional methods. In this paper, a new approach for generating woodgrain patterns is proposed. Virtual trees are generated by simulating tree growth in consideration of environmental conditions. Moreover, fine tree tissues and reflection properties at the wood surface are modeled. By applying these modeled factors, more diverse and accurate woodgrain patterns can be generated. With this approach, various types of virtual trees can be obtained by changing growth conditions such as period and location of growth or form of tissue in trees without the need to reset complicated parameters of each tree species. After this, the virtual trees can be cut at arbitrary areas, thus allowing a variety of woodgrain patterns to be generated by easy parameter setup.