Physically-based Driven Tree Animations

Abstract

Simulating dynamic natural wind effects on trees remains a challenging task in Computer Graphics. From an animator s point of view it is a cumbersome and tedious task to create this effect due to the complexity of the tree shape, the numerous protruding branches and the wide variety of foliage. In this paper we present a novel method to create controllable animations of trees. Our approach borrows from several ideas from video textures, computer-assisted animation and motion graphs. It combines re-sequencing of existing material with the automatic generation of new data. Furthermore, the animator can direct the animation at each arbitrary moment using a goal based motion algorithm. First, a small set of motion data is gathered from a physically-based driven tree animation. Next, an optimised motion graph is constructed from the acquired data indicating all possible transitions from one tree pose to another. By creating in-between frames for all pairs of keyframes we ensure smooth transitions. Finally, by walking on the motion graph new non-identical animations are synthesised. The resulting animations are smooth, controllable by the animator and suitable for different production targets including 3D virtual environments (e.g., games) and 2D stylised animation.