GRAIL: Generating Humanoid Loco-Manipulation from World Models

CoRL 2026 Best Paper Award Finalist

Tianyi Xie1,2,*   Haotian Zhang1,*   Jinhyung Park1,*   Zi Wang1,*   Bowen Wen1   Jiefeng Li1   Xueting Li1   Qingwei Ben1  
Haoyang Weng1   Yufei Ye1   David Minor1   Tingwu Wang1   Chenfanfu Jiang2   Sanja Fidler1  
Jan Kautz1   Linxi "Jim" Fan1   Yuke Zhu1   Zhengyi Luo1,†   Umar Iqbal1,†   Ye Yuan1,†  
1 NVIDIA     2 UCLA
* Co-First Authors     † Project Leads
NVIDIA UCLA

Abstract

Scaling humanoid loco-manipulation requires robot-compatible demonstrations across diverse objects, whole-body motions, and scene geometries, but teleoperation and motion capture are difficult to scale because each collection depends on physical setups, instrumented actors, and robot operation. We present GRAIL, a digital generation pipeline that remains fully virtual until deployment: it grounds video world models in 3D assets and simulator-ready scenes to synthesize interactions without rebuilding physical environments or teleoperating the robot.

Rather than reconstructing unconstrained in-the-wild videos, GRAIL starts from fully specified 3D configurations in which object geometry, camera parameters, metric scale, environment depth, and a robot-proportioned character are known before video generation and reused during reconstruction. This privileged setup better conditions 4D recovery, allowing model-based object tracking, human motion estimation, and interaction-aware optimization to reconstruct metric 4D human-object interaction (HOI) trajectories with reduced depth ambiguity and morphology mismatch. We retarget the recovered motions to a humanoid robot and train complementary task-general trackers: an object-aware latent adaptor for manipulation and a scene-aware tracker for terrain traversal.

Motion Gallery

GRAIL now includes over 35,000 physically validated motions, covering both object-centric interactions and scene-centric whole-body motion. The gallery below shows object manipulation and scene-aware locomotion as two complementary capability blocks.

Large-Scale Stair Traversal

Generated motions adapt to diverse stair geometries, materials, and step heights.

Scene-aware humanoid traversal across procedurally generated staircases.

Sim-to-Real Deployment

We deploy policies trained with GRAIL-generated data on a real Unitree G1, covering egocentric RGB-based pick-up and stair-climbing.

Rendered Egocentric Views for Policy Training

GRAIL renders egocentric RGB videos from generated grasping demonstrations, providing visual-policy training data before transferring the policy to real-world deployment.

Parallel simulation environments
Rendered egocentric RGB across randomized scenes

Egocentric Visual Policy Deployment

We train egocentric RGB policies on GRAIL-generated data and deploy them on a Unitree G1 for real-world object pick-up and stair-climbing.

Real-world pick-up

Real-world stair-climbing

Real-world deployment in diverse environments

Method

GRAIL grounds video world models in fully specified 3D scenes. It first renders a scene with known object geometry, camera parameters, metric scale, and a robot-proportioned character, then uses a video world model to roll out a human-object interaction. It recovers metric 4D motion within this known scene and retargets it to the Unitree G1, where complementary task-general trackers turn the references into robot-action data for downstream visual policy learning.

A video world model generates an interaction from a known 3D scene; pose estimation, object tracking, and joint optimization recover metric 4D human-object motion
Asset-conditioned 4D HOI generation. A character prefitted to the target humanoid and a known 3D object are placed in a simulator-ready scene. A video world model generates a static-camera interaction from the rendered first frame. Human pose estimation and model-based object tracking initialize the trajectories; joint optimization refines them with keypoint, depth, and contact losses anchored to the known scene, reducing depth ambiguity and morphology mismatch.

Metric 4D Reconstruction

Recovered human and object motion stays aligned with the generated interaction video within the known metric scene, across manipulation, stair traversal, and sitting.

Generated video Metric 4D reconstruction
Video 4D
Task-general humanoid tracking and policy adaptation pipeline
Task-general tracking. Retargeted 4D HOI trajectories are converted into robot-action data by adapting complementary parts of a pretrained whole-body controller, enabling object-aware manipulation policies and scene-aware locomotion policies for terrain traversal and sitting.

Loco-Manipulation at Scale

A continuous view of generated humanoid behaviors across object manipulation, sitting, and terrain traversal, from individual interactions to a broad collection of motions.

BibTeX

If you find GRAIL useful in your research, please cite:

@inproceedings{grail2026,
  title     = {{GRAIL}: Generating Humanoid Loco-Manipulation from World Models},
  author    = {Tianyi Xie and Haotian Zhang and Jinhyung Park and Zi Wang and
               Bowen Wen and Jiefeng Li and Xueting Li and Qingwei Ben and
               Haoyang Weng and Yufei Ye and David Minor and Tingwu Wang and
               Chenfanfu Jiang and Sanja Fidler and Jan Kautz and Linxi Fan and
               Yuke Zhu and Zhengyi Luo and Umar Iqbal and Ye Yuan},
  booktitle = {Conference on Robot Learning (CoRL)},
  year      = {2026},
  url       = {https://arxiv.org/abs/2606.05160},
}