Abstract: Based on 3D Delaunay theory, an optimal α is selected to construct the minimal connected
α-shape from the input point cloud of a tree model. After the calculation and filtering of its distance
field, a smooth distance surface is extracted, from which the bounding volumes of tree trunk and
crown are segmented respectively based on the Laplacian skeleton-based segmentation approach.
Finally, the point cloud within the crown volume is utilized to generate multi-resolution α-shapes,
which can be used as levels of detail (LOD) models in non-photorealistic VR environment.

Key words: α-shape, levels of detail, virtual reality, crown modeling