Learning from demonstration (LfD) has enabled humanoid robots to acquire diverse whole-body skills, but extending this paradigm to human-object interaction (HOI) is limited by the availability of robot-compatible interaction references. We present HOI-Retarget, a contact-centric retargeting method that transfers HOI onto a humanoid robot for large-scale motion-data generation. Its windowed trajectory optimization uses every labeled contact as a target in the object frame, balancing body tracking, foot support and smoothness under the robot's kinematic limits. The method can augment a single demonstration across object sizes, absorb contacts reconstructed from monocular video, and extend to several robots manipulating one object. We publicly release the code and the retargeted motion dataset.
Figures & tables
Fig. 2: Overview of HOI-Retarget . (a) The source is a captured or video-reconstructed HOI clip, providing human motion, an object trajectory and contact labels. (b) IK retargeting maps the human onto the robot, while the object mesh and trajectory are scaled by the robot-to-human height ratio, carrying the contact targets with them. (c) A windowed trajectory optimization with tracking, contact and smoothness costs recovers those contacts under the robot’s kinematic limits. (d) The result drives downstream policies directly, or after dynamic refinement in simulation.
Method
Source Human Motion
Object Interaction
Contact Location Preservation
Data Augmentation
Multi-Agent Source
Temporal Coupling
Dynamics Enforcement
Optimization Method
GMR [ 11 ]
✓
✗
✗
✗
✗
✗
✗
per-frame IK
OmniRetarget [ 13 ]
✓
✓
✗
✓
✗
✗
✗
per-frame SOCP
DynaRetarget [ 14 ]
✗
✓
✗
✓
✗
✓
✓
progressive SBTO
SPIDER [ 15 ]
✗
✓
✗
✓
✗
✓
✓
receding-horizon sampling
HOI-Retarget (ours)
✓
✓
✓
✓
✓
✓
✗
windowed NLP
TABLE I: Capabilities of representative retargeting methods.
Cost term
Symbol
Definition
w
Tracking
ET
Eθ+Eb+Eh+Ef+Er
Joint position
Eθ
∥θ−θ∗∥2
1
Base position
Eb
∥pbw−pbw∗∥2
1
Head position
Eh
∥pheadw−pheadw∗∥2
1
Feet position
Ef
∑i∈F∥pc,iw−pc,iw∗∥2
100
Torso orientation
Er
∥Rtorsob−Rtorsob∗∥F2
1
TABLE II: Cost terms of ( 2 ), grouped as in ( 2a ).
Fig. 3: Representative retargets across HOI sources and embodiments. Rows show the source SMPL-X motion, Unitree G1, and Unitree H2.
Metric
GMR
OmniRetarget
Ours
Body pose deviation ( ∘ ) ↓
20.0
25.0
21.0
Link vel. direction ( ∘ ) ↓
19.4
28.9
25.2
Contact-point gap (m) ↓
0.368
0.183
0.005
Rel. hand-orient. change ( ∘ ) ↓
2.3
37.6
6.1
Body jerk (m/s 3 ) ↓
66.7
193.5
49.9
Compute time (s/clip) ↓
9.1
156.2
33.7
TABLE III: Kinematic retargeting on the common OMOMO subset (3,997 clips; 3,604 for contact metrics).
Fig. 4: Qualitative comparison with OmniRetarget. HOI-Retarget recovers the labeled source contact regions on the coat rack and chair.
Fig. 5: Contact-preserving object-scale augmentation over the tested range ×0.25 – ×1.50 on the G1 and H2.
RL Tracker
SBTO
Metric
Omni.
Ours
Omni.
Ours
Body pose deviation ( ∘ ) ↓
26.5
23.5
26.0
23.1
Link vel. direction ( ∘ ) ↓
47.9
46.7
51.2
50.8∗
Object path err. (m) ↓
0.285
0.213
0.269
0.194
Contact-point gap (m) ↓
0.096
0.086
0.141
0.099
Rel. hand-orient. change ( ∘ ) ↓
31.5
25.3
38.4
28.1
TABLE IV: Dynamic-refinement quality on the common subset (68 clips; 63 for contact metrics).
Fig. 6: Example of using HOI-Retarget from video reconstruction using CARI4D. Contact refinement tool has been used to account for monocular reconstruction artifacts.
Appendix figures & tables3 assets
Supplementary material from the paper’s appendix.
Appendix
Symbol
Description
(⋅)∗
Reference quantity
(⋅)h
Human source quantity
(⋅)w,(⋅)b,(⋅)o
World, base, object frame
δ(⋅)
Backward difference,
δ(⋅)t=(⋅)t−(⋅)t−1
q
Configuration (pbw,Rbw,θ)
Appendix
TABLE V: Symbols used for HOI-Retarget.
Metric
Definition
Body pose deviation ( ∘ )
Mean over frames of the mean angle between the robot’s and the human’s 16 bone directions, taken in the pelvis frame for the legs and the trunk frame for the arms.
Link vel. direction ( ∘ )
Mean angle between the robot’s and the human’s object-relative link velocity Row⊤(p˙w−p˙ow) , over the palms, ankles, head and pelvis, where both exceed 2 cm/s.
Contact-point gap (m)
Mean distance on the object between the robot’s palm and the human’s contact point ( 1 ), over frames in contact. This is the residual Ec minimizes.
Rel. hand-orient. change ( ∘ )
Mean angle between the robot’s and the human’s change in palm orientation in the object frame since the first frame of the contact segment.
Object path err. (m)
Mean distance between the robot-side and the human-side object translation, each taken relative to its own first frame.
Body jerk (m/s 3 )
Mean magnitude of the third difference of world link position, over links and frames.
Appendix
TABLE VI: Evaluation metrics reported in Tables III and IV .
Horizon
Coll.
Solved
Time (s)
RAM (MB)
Link vel. dir. ( ∘ )
Joint jerk (rad/s 3 )
Per-frame
✗
130/130
37.7
1440
40.3
588
Windowed
✗
130/130
39.4
1763
24.4
251
✓
130/130
159.9
3876
24.5
257
Full traj.
✗
130/130
45.8
2400
23.5
185
✓
87/130
210.5
8671
24.4
186
Appendix
TABLE VII: Optimization horizon, with and without the collision cost.
The Hong Kong University of Science and Technology (Guangzhou) · Artificial General Intelligence Institute, University of Science and Technology of China · The University of Hong Kong +1