ScaffoldTree: Scaffold-to-Subtree Diffusion for 3D Tree Generation

We present ScaffoldTree, a species-conditioned diffusion framework for structured 3D tree generation. ScaffoldTree decomposes a tree according to the structural roles of its branches: the trunk and major branches form a global scaffold, while fine-scale branches are represented as locally attached residual subtrees. Global Scaffold Diffusion first generates the scaffold by jointly modeling branch curves, attachment locations, and parent relationships. The Structure-Conditioned Residual Allocator then predicts the total number of residual branches from the generated scaffold and distributes them across scaffold anchors. Conditioned on the scaffold and allocation, Local Residual Diffusion generates the corresponding residual subtrees, which are hierarchically transformed according to their predicted parent–child relations and merged with the scaffold to form the complete tree. This decomposition separates global tree organization from local branching detail while maintaining their structural dependence. Experiments demonstrate improved structural and local-curve distribution matching and reference coverage compared with the evaluated baselines.