改进自回归绑定模型,实现复杂植物骨架的精准重建。
PlantRig - From Bones to Branches: Adaptation of Autoregressive Rigging Models for Plant Skeletal Reconstruction

- 通过多轮微调提升模型对植物分支结构的建模能力。
- 在真实扫描与合成数据上成功恢复复杂分支拓扑,包括带叶植物。
- 无需针对叶片设计特殊结构,可泛化至多种植物形态。
自回归绑定模型如UniRig和SkinTokens在人物关节结构上表现良好,但其在植物结构上的泛化能力尚未充分探索,因植物拓扑具有高度可变、非标准的分枝模式,挑战了已有骨骼先验。本文使用合成的L系统生成树与真实扫描数据(涵盖单干、合轴、轮生及藤本等类型)评估这些模型。初步测试显示,UniRig将复杂分枝坍缩为近线性链,而SkinTokens虽更好保留拓扑但过度分割分支且输出不稳定,因此聚焦于UniRig的稳定性。诊断发现崩溃源于分支标记在采样层面被抑制,进一步分析表明冻结的网格编码器对结构变化敏感度有限,暴露了标记流程中的几何瓶颈而非单纯学习偏差。基于此,我们在多个程序生成的合成数据集上进行多轮微调,模型逐步恢复准确的分枝拓扑,并扩展到含叶植物这一更难情形——尽管叶片为零厚度、依赖网格法向,仍取得良好效果。最终模型在无叶结构修改下广泛泛化于多种植物形态,表明针对性微调可显著缩小角色绑定先验与植物骨架结构之间的领域差距。本工作为自动植物绑定提供了可行路径,涵盖分支拓扑与叶型,即便未在研究中覆盖的类型亦可适用。
原文摘要 · Abstract (English)
Autoregressive rigging models such as UniRig and SkinTokens perform well on articulated characters, but their ability to generalize to plant structures remains largely unexplored, since plant topologies exhibit highly variable, non-canonical branching patterns that challenge learned skeletal priors. We evaluate these models for plant skeletal reconstruction using synthetic L-system-generated trees and real scanned data spanning monopodial, sympodial, whorled, and vine-like archetypes. Preliminary testing showed UniRig collapsing complex branching into near-linear chains, while SkinTokens preserved topology better but over-segmented branches and produced an unstable output space, so we focused on UniRig for its greater stability. Diagnosis traced the collapse to sampling-level suppression of branch tokens, and further analysis showed the frozen mesh encoder had limited sensitivity to structural variation, pointing to a geometric bottleneck in the tokenization pipeline rather than a purely learned bias. Building on these findings, we applied multi-round fine-tuning over multiple procedurally generated synthetic datasets. Across rounds, the model progressively recovered accurate branching topology and generalized beyond branch-only structures to plants with foliage, a harder case given the zero-thickness, mesh-normal-dependent geometry of leaves. The resulting model generalized well across diverse plant forms without leaf-specific architectural changes, indicating that targeted fine-tuning can substantially close the domain gap between character-rigging priors and plant skeletal structure. As such, our work points toward a viable path for automated plant rigging across both branch topology and foliage type, even those not considered in our findings.
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