OmniMM: A Unified Language-Motion Model with Biomechanical Skeleton Motion

Recent progress in multimodal human motion modeling has enabled increasingly capable systems for generating and understanding motion, yet most operate in surface-driven parametric representations that are not designed to faithfully reflect human skeletal anatomy. We introduce **Omni-Motion Model (OmniMM)**, a unified framework that treats anatomy-driven biomechanical skeleton motion as a first-class modality alongside conventional parametric motion and language. OmniMM jointly models these modalities, enabling motion generation, motion understanding, bidirectional cross-representation fitting, and synchronized joint generation within a single model. To make this possible at scale, we construct paired parametric–biomechanics–language data by recovering biomechanical skeleton motion from existing SMPL sequences while preserving their original annotations. OmniMM models continuous motion representations with modality-specific Transformer towers coupled through shared attention, enabling specialized modeling while supporting cross-modal interaction. Experiments demonstrate effective modeling and translation across semantic, surface-driven, and anatomy-driven motion spaces, including the generation of parametric motion aligned with its corresponding biomechanical skeleton motion.