Dream4ACT: A Shared Visual Action Interface for Multi-Embodiment Video-Action Modeling

Xiangyu Zhu; Jin Xu; Yue Guo; Xin Wu; Yifan Sun; Xiancong Ren; Jianxin Sun; Yong Dai

cs.ROSep 30, 2026

Dream4ACT: A Shared Visual Action Interface for Multi-Embodiment Video-Action Modeling

Authors: Xiangyu Zhu, Jin Xu, Yue Guo, Xin Wu, Yifan Sun, Xiancong Ren, Jianxin Sun, Yong Dai, +1 more

Organizations: Beijing Humanoid Robot Innovation Center · Beijing Institute of Technology · Harbin Institute of Technology, Shenzhen · The University of Hong Kong · China University of Mining & Technology, Beijing

Abstract

Video generation models (VGMs) offer strong spatiotemporal priors for embodied observation--action modeling. However, joint-space action vectors lack explicit image-space structure and vary in dimensionality and semantics across embodiments, making it challenging to directly leverage the rich spatiotemporal priors of VGMs. End-effector visualizations provide an alternative but do not specify the full articulated configuration needed for robot execution. We present Dream4ACT, a world model built for joint video-action modeling across embodiments. To unify action representations across embodiments, we introduce a shared visual action interface, called action views, which render target joint configurations from four prescribed virtual cameras using URDF-based forward kinematics. This shared visual representation preserves embodiment-specific articulated geometry while allowing observation and action sequences to share a video autoencoder and diffusion transformer. Through masked flow-matching, our model supports forward dynamics, inverse dynamics, and joint observation--action generation within a single jointly trained model by varying which future sequences are corrupted. To recover executable action sequences from predicted action views, we propose a training-free, URDF-constrained multiview recovery mechanism, without a learned embodiment-specific decoder. Dream4ACT achieves an average success rate of 88.98% on RoboTwin~2.0 and an overall score of 65.66 on TriWorldBench, supporting effective closed-loop manipulation and competitive action-conditioned multiview prediction through the visual action interface.

Figures & tables

Figure 1 : Overview of Dream4ACT. Top: A shared action-view interface supports forward dynamics, inverse dynamics, and joint generation, with training-free recovery of joint targets. Bottom left: Examples of multi embodiments real-world task execution. Bottom right: Success rates and scores show strong performance in both robotic manipulation and action-conditioned video generation.

Figure 2 : Architecture of Dream4ACT. (a) URDF-based rendering produces four action views. (b) A shared video VAE and diffusion transformer model RGB observations and action views with VLM-derived semantic conditioning, here we show the joint generation mode. (c) Training-free multiview action solver recovers joint targets from predicted views.

Mode	$M$	RGB streams ( $f\geq 1$ )	Action views ( $f\geq 1$ )
Forward dynamics	$\mathcal{S}_{\mathrm{rgb}}$	noised	clean
Inverse dynamics	$V$	clean	noised
Joint generation	$\mathcal{S}$	noised	noised

Table 1 : Mode-specific generation choices. Frame

f=0

always remains clean.

Input: Predicted action views

\{\hat{x}^{i}_{t^{\prime}}\}_{i\in V,\,t^{\prime}=t+1:t+k}

; embodiment-specific URDF

U

; virtual cameras parameters

\{K_{i},T_{i}\}_{i\in V}

; current state

S_{t}

; foreground threshold

\eta

, dilation radius r, and update stride

\lambda

Output: Recovered predicted trajectory

\hat{A}_{t+1:t+k}

\hat{A}_{t}\leftarrow S_{t}

for

t^{\prime}=t+1,\ldots,t+k

\tilde{x}^{i}_{t^{\prime}}\leftarrow\mathrm{dil}\big(\mathbbm{1}\big[\hat{x}^{i}_{t^{\prime}}>\eta\big];r\big)

for every

i\in V

Sample candidate and render corresponding action-views using Equation 4 .

Calculate score

E_{t^{\prime}}

using Equation 16 .

Table 2 : Algorithm for training-free action recovery.

Method	Clean	Randomized	Avg.
$\pi_{0.5}$ ( Intelligence et al., 2025 )	82.74	76.76	79.80
Motus ( Bi et al., 2026 )	88.66	87.02	87.80
LingBot-VA ( Li et al., 2026b )	92.90	91.50	92.20
Fast-WAM ( Yuan et al., 2026 )	91.88	91.78	91.80
Ours	90.50	87.46	88.98

Table 3: Success rates (%) on RoboTwin2.0 over 50 clean and 50 randomized tasks. Table 10 presents a comparison of success rates for each individual task.

Model	TVC	TA	P3D	MQ	TC	VQ	Overall
Ctrl-World ( Guo et al., 2026 )	$57.42$	$43.72$	$34.67$	$29.28$	$46.17$	$16.64$	$38.98$
Motus ( Bi et al., 2026 )	$66.70$	$49.69$	$34.60$	$24.63$	$26.56$	$16.26$	$42.35$
Genie Envisioner ( Liao et al., 2026 )	$62.39$	$33.17$	$54.00$	$20.17$	$32.18$	$17.46$	$40.73$
DreamDojo ( Gao et al., 2026 )	$69.63$	$56.24$	$43.84$	$27.96$	$60.84$	$21.02$	$51.72$
BWM ( Team and others, 2026 )	81.87	$\mathbf{86.05}$	$60.40$	$41.29$	$62.81$	31.42	$65.54$
Ours	$81.63$	$84.22$	$\mathbf{61.30}$	41.66	64.88	31.42	65.66

Table 4: TriWorldBench results . Dream4ACT is evaluated on the official 500-episode test set and reports six key indicators.

Robot	Clean	Random	Position (mm) $\downarrow$	Rotation ( ∘ ) $\downarrow$	Avg $\uparrow$
Aloha-Agilex	81.94	82.45	1.39	1.57	82.19
Piper	81.55	82.32	1.66	1.71	81.94
ARX-X5	82.19	80.26	1.22	1.95	81.23
Franka-Panda	64.52	62.45	4.11	9.45	63.48
UR5-Xsg	31.87	30.06	11.85	21.39	30.97

Table 5: Success rates (%) and end-effector recovery errors of the same jointly trained checkpoint across five embodiments on 31 shared RoboTwin 2.0 tasks. We use 25 trials per task and setting, Avg combines Clean and Randomized results. Recovery errors use GT action views with five held-out trajectories per task and 40 future frames per window, aggregated with equal task weighting.

Robot	Place_block	Wipe_plate	Stack_blocks	Storage_item	Common	All
Aloha-Agilex	85.0	90.0	20.0	50.0	87.5	61.3
TienYi2.5 Pro	90.0	80.0	30.0	65.0	85.0	66.3
Franka	90.0	85.0	–	–	87.5	–
UR5e	85.0	95.0	–	–	90.0	–

Table 6: Real-world success rates (%) using the same jointly trained checkpoint across four robot platforms. Each embodiment–task pair is evaluated over 20 trials under scene variations, including randomized background and randomized distractor objects. Common averages the first two tasks; All averages all tasks evaluated on each platform. “–” denotes a task not evaluated on that platform.

Figure 3 : Comparison of conditioning representations. The same recorded joint configurations are represented as camera-aligned skeleton projections or action-view renderings from four prescribed virtual cameras.

Method	DROID
Method	PSNR $\uparrow$	SSIM $\uparrow$	LPIPS $\downarrow$
Skeleton rendering	23.19	0.899	0.105
Action-view rendering (Ours)	24.33	0.906	0.093

Table 7: RGB prediction fidelity on 50 held-out DROID trajectories from CLVR and RAD. Both variants condition on recorded joint states and predict 41-frame sequences.

Appendix figures & tables7 assets

Supplementary material from the paper’s appendix.

Appendix

Figure 4 : Trainable adapter modulates main view and instruction information.

Hyperparameter	Value
Training Resource	$16\times\text{Nvidia B200}$
Batch Size	16
Optimizer	AdamW
Weight Decay	$1\times 10^{-2}$
Learning Rate	$1\times 10^{-5}$
Learning Rate Scheduler	Cosine Scheduler

Appendix

Table 8: Training hyperparameters.

Figure 5 : Real-world robots hardware configuration. Franka and UR embodiment use one front camera and one wrist camera, while Aloha-Agilex and TienYi use one head camera and two wrist cameras.

Embodiment	Position (mm) $\downarrow$	Rotation ( ∘ ) $\downarrow$	Avg. success (%) $\uparrow$
Aloha-Agilex	1.39	1.57	82.19
Piper	1.66	1.71	81.94
ARX-X5	1.22	1.95	81.23
Franka-Panda	4.11	9.45	63.48
UR5-Xsg	11.85	21.39	30.97

Appendix

Table 9: Action recovery errors and task success across five embodiments on 31 shared RoboTwin 2.0 tasks. Avg. success averages Clean and Randomized evaluations, with 25 trials per task, per embodiment, and per setting.

Simulation Task	$\pi_{0.5}$		Motus		LingBot-VA		Fast-WAM		Ours
Simulation Task	Clean	Rand.	Clean	Rand.	Clean	Rand.	Clean	Rand.	Clean	Rand.
Adjust Bottle	100%	99%	89%	93%	90%	94%	100%	100%	91%	97%
Beat Block Hammer	96%	93%	95%	88%	96%	98%	99%	97%	100%	96%
Blocks Ranking RGB	92%	85%	99%	97%	99%	98%	100%	100%	96%	90%
Blocks Ranking Size	49%	26%	75%	63%	94%	96%	94%	98%	62%	58%
Click Alarmclock	98%	89%	100%	100%	99%	100%	100%	100%	100%	100%

Appendix

Table 10 : Per-task success rates (%) on the 50-task RoboTwin 2.0 benchmark under clean and randomized (Rand.) settings. Baseline scores are taken from publicly reported results. Bold marks the highest score for each task and setting.

Simulation Task	Aloha		Franka		Piper		ARX-X5		UR5
Simulation Task	Clean	Random	Clean	Random	Clean	Random	Clean	Random	Clean	Random
Beat Block Hammer	100%	100%	60%	64%	60%	76%	56%	68%	56%	48%
Blocks Ranking RGB	0%	0%	0%	0%	4%	0%	0%	0%	0%	0%
Blocks Ranking Size	64%	64%	68%	56%	80%	84%	52%	60%	12%	8%
Grab Roller	100%	96%	96%	96%	100%	100%	100%	100%	32%	48%
Handover Mic	80%	80%	40%	28%	96%	100%	100%	96%	48%	40%

Appendix

Table 11 : Per-task success rates (%) across five robot embodiments on 31 shared RoboTwin 2.0 tasks under clean and randomized settings. Each task is evaluated over 25 episodes per embodiment and setting.

Figure 6 : Execution progress of real-world manipulation tasks. Each row shows representative temporal snapshots for one task, illustrating how the robot complete place_block, wipe_plate, stack_blocks, and storage_item.

Explore similar work

Jun 2, 2026cs.RO

PointAction: 3D Points as Universal Action Representations for Robot Control

Video-Action Models (VAMs) leverage the broad visual dynamics captured by pre-trained video diffusion models, offering a promising path toward generalizable robot manipulation. However, RGB-only video rollouts are not directly actionable: they leave metric 3D motion, contact geometry, and fine-grained spatial constraints under-specified, making action grounding ambiguous. Meanwhile, scaling action supervision across diverse tasks and embodiments remains costly. We present PointAction, a framework that bridges video predictions to robot actions through explicit point-based 4D modeling. PointAction fine-tunes a foundation video generation model to jointly predict future RGB frames and dynamic 3D pointmaps, producing temporally consistent 3D motion of task-relevant scene geometry. These point dynamics serve as a structured, embodiment-agnostic action interface, which a diffusion-based action decoder maps to executable robot actions. By using metric 3D point dynamics as the interface between video prediction and control, PointAction reduces the ambiguity of RGB-only action grounding and supports transfer across tasks and embodiments with limited action supervision. Experiments show that PointAction achieves state-of-the-art 4D generation quality on robot scenes, outperforms existing baselines in simulation, and generalizes to two real robot arms unseen during pretraining.

Mutian Tong, Han Jiang, Qiao Feng +2

University of Pennsylvania · Work done during internship at University of Pennsylvania.

Robotic Manipulation 3D Motion Action Expert Diffusion Policies Video Diffusion Models Unified Representation

Ask PDF

Aug 13, 2026cs.CV

DreamX-Phi 1.0: Action-Conditioned Video World Model for Robotic Manipulation

We present \textbf{DreamX-Phi 1.0}, an action-conditioned video world model for robotic manipulation that, given an observed frame, a language instruction, and a prescribed action sequence comprising end-effector poses and gripper states, predicts the resulting future observations. Yet realism alone does not guarantee faithfulness: a convincing rollout can still move the wrong arm or lose the manipulated object. To ensure the prediction respects each arm's commanded path, we inject per-arm

\mathrm{SE}(3)

transformations into attention via \textbf{PRoPE-style geometric encoding}, preserving arm identity and rigid-motion structure. Action control alone does not fully constrain scene geometry or the evolution of small manipulated objects. We therefore add a lightweight \textbf{depth branch} for scene-level geometry and use \textbf{SAM3 masks} with a frozen \textbf{V-JEPA teacher} to maintain object consistency throughout grasping. We further distill the multi-step generator into a few-step student via distribution-matching distillation for efficient deployment. At the time of writing, \model{} achieves first place on Track~~1 and second place on Track~~2 of the WorldArena~2.0 Challenge. Our model and code will be publicly available.

DreamX Team, Rui Chen, Xiangxiang Chu +7

Efficient World-Action Model Robotic Manipulation Video World Models End-Effector Pose Dream World

Ask PDF

Apr 30, 2026cs.RO

Motubrain: An Advanced World Action Model for Robot Control

Vision-Language-Action (VLA) models generalize semantically well but often lack fine-grained modeling of world dynamics. We present Motubrain, a unified World Action Model that jointly models video and action under a UniDiffuser formulation with a three-stream Mixture-of-Transformers architecture. A single model supports policy learning, world modeling, video generation, inverse dynamics, and joint video-action prediction, while scaling to heterogeneous multimodal data such as video-only, task-agnostic, and cross-embodiment robot data. Building on Motus, Motubrain further introduces unified multiview modeling, an independent text stream for stronger language-action coupling, a shared cross-embodiment action representation, and an efficient post-training and deployment recipe for long-horizon real-world control. Our inference stack combines step reduction, compilation, FP8 quantization, DiT caching, V2A-style action-only inference, and real-time chunked closed-loop execution, achieving over 50x speedup over a naive baseline and up to 11 Hz inference. Experimentally, Motubrain achieves 95.8% and 96.1% average success on RoboTwin 2.0 under clean and randomized settings, respectively, attains the strongest reported EWMScore in our WorldArena comparison, and adapts to new humanoid embodiments with only 50--100 trajectories. These results show that unified world action models can scale in generality, predictive accuracy, and real-world deployability.

Motubrain Team, Chendong Xiang, Fan Bao +17

Motubrain Team

Diffusion-Based Vision-Language-Actions Recent World-Action Models Robot Systems Transformer Architectures

Ask PDF