Absolute Coordinates Make Motion Generation Easy
Authors: name: Zichong Meng; name: Zeyu Han; name: Xiaogang Peng; name: Yiming Xie; name: Huaizu Jiang
Published: 2025-05-26 00:36:00

Abstract: State-of-the-art text-to-motion generation models rely on the
kinematic-aware, local-relative motion representation popularized by HumanML3D,
which encodes motion relative to the pelvis and to the previous frame with
built-in redundancy. While this design simplifies training for earlier
generation models, it introduces critical limitations for diffusion models and
hinders applicability to downstream tasks. In this work, we revisit the motion
representation and propose a radically simplified and long-abandoned
alternative for text-to-motion generation: absolute joint coordinates in global
space. Through systematic analysis of design choices, we show that this
formulation achieves significantly higher motion fidelity, improved text
alignment, and strong scalability, even with a simple Transformer backbone and
no auxiliary kinematic-aware losses. Moreover, our formulation naturally
supports downstream tasks such as text-driven motion control and
temporal/spatial editing without additional task-specific reengineering and
costly classifier guidance generation from control signals. Finally, we
demonstrate promising generalization to directly generate SMPL-H mesh vertices
in motion from text, laying a strong foundation for future research and
motion-related applications.