Tree models can be categorized into two classes: global models that represent the developmental form of the entire tree, and local models that represent the geometric details found on the tree surface and leaves. This paper presents new implicit local tree modeling techniques. An existing generalized cylinder blending model is extended to blend eccentric cones, to simulate the reaction wood trees generate at branching points. The bark of trees has been observed to follow the force ow lines of the tree, and a
particle ow approximation is used to simulate the texturing of bark on trees at branching points. Since trees are commonly identified by the appearance of their bark, we have also attempted to model bark that is typical of a particular species, rather than just realistic in general.