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Sparse2Act: Learning Action-Aligned Sparse 3D Representations for Cross-Domain Robot Manipulation

Summary

Sparse2Act is a pretraining framework that uses task-space end-effector actions as geometric supervision to align sparse point-cloud encoders with observations. It achieves 86.9% success on LIBERO-10, 73.4% cross-domain on Meta-World-5, and 72.5% on real-world tasks.

SourcearXiv RoboticsAuthor: Yu Guo, Chang Yu, Siyu Ma, Yunuo Chen, Yin Yang, Ying Nian Wu, Chenfanfu Jiang
Sparse2Act: Learning Action-Aligned Sparse 3D Representations for Cross-Domain Robot Manipulation
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[2606.12759] Sparse2Act: Learning Action-Aligned Sparse 3D Representations for Cross-Domain Robot Manipulation

[Submitted on 10 Jun 2026]

Title:Sparse2Act: Learning Action-Aligned Sparse 3D Representations for Cross-Domain Robot Manipulation

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Abstract:Explicit 3D representations are attractive for manipulation because they expose object shape, workspace geometry, and robot-object relations in metric coordinates. However, sparse 3D encoders are often learned through downstream task objectives, tying the representation to a particular data distribution, policy architecture, and action parameterization. We introduce Sparse2Act, an observation-action alignment framework for pretraining sparse point-cloud encoders. The key idea is to use task-space end-effector actions as geometric supervision: masked sparse 3D tokens are trained to organize scene features around the workspace motion paired with the observation. After pretraining, only the encoder initialization is reused by downstream policies, allowing them to retain their own architectures and action spaces, including joint-space commands. On the LIBERO-10 benchmark, our method achieves 86.9% average success after 500 fine-tuning steps. The same pretrained encoder supports LIBERO-to-Meta-World cross-domain transfer, achieving 73.4% average success on the Meta-World-5 benchmark. Ablations on the objective and decoder capacity show that the gains come from the masked action-alignment signal and remain useful across downstream action decoders. In real-world experiments, simulation pretraining followed by limited real-data fine-tuning achieves an average success rate of 72.5% across four tasks, demonstrating effective sim-to-real transfer. These results suggest that robot actions can provide compact geometric supervision for reusable sparse 3D representations.

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Robotics (cs.RO)

Cite as: arXiv:2606.12759 [cs.RO]

(or arXiv:2606.12759v1 [cs.RO] for this version)

https://doi.org/10.48550/arXiv.2606.12759

arXiv-issued DOI via DataCite (pending registration)

Submission history

From: Chang Yu [view email] [v1] Wed, 10 Jun 2026 23:56:01 UTC (13,986 KB)

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Key points

  • Sparse2Act pretrains sparse 3D encoders with action-aligned masked signals for reusability.
  • Reaches 86.9% average success on LIBERO-10 with only 500 fine-tuning steps.
  • Supports cross-domain transfer from LIBERO to Meta-World, achieving 73.4% average success.
  • Sim-to-real transfer yields 72.5% average success on four real-world tasks with limited fine-tuning.

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