Sketch-based Shape-preserving Tree Animations


Computer Animation and Virtual Worlds, 2018, 29(3-4): e1821. (Best Paper Award for CASA'2018)

Yutong Wang, Luyuan Wang, Zhigang Deng and Xiaogang Jin

teaser image

Figure 1. Shape-preserving transformations of a sphere-shaped Salix into a heart-shaped one.

omparison between our method (bottom row) and topologically consistent morphing

Figure 2. Comparison between our method (bottom row) and topologically consistent morphing [7] (top row). The latter generates less meaningful inbetween crowns due to the branch correspondences unaware of crown’s morphological meanings.


We present a novel and intuitive sketch-based tree animation technique, targeting on generating a new type of special effect of smoothly transforming leafy trees into morphologically different new shapes. Both topological consistencies of branches and meaningful inbetween crown shapes are preserved during the transformation. Specifically, it takes a leafy tree and a user’s sketch describing the silhouette of the desired crown shape under a certain viewpoint as the input. Based on a self-adaptive multiscale cage tree representation, branches are locally transformed through a series of topology-aware deformations, and the resulting tree conforms to the user-designed shape, demonstrating better aesthetics compared to global single cage-based methods. By interpolating the transformations, we are able to create visually pleasing shape preserving animations of trees transforming between two crown shapes. Our proposed framework also provides an efficient way to interactively edit leafy trees towards desired shapes, demonstrating its potential to leverage existing tree modeling frameworks by providing flexible and intuitive tree editing operations.