ResWM: Residual-Action World Model for Visual RL
Organizations: University of California, San Diego USA · Texas A&M University-Commerce USA
Abstract
Learning predictive world models from raw visual observations is a central challenge in reinforcement learning (RL), especially for robotics and continuous control. Conventional model-based RL frameworks directly condition future predictions on absolute actions, which makes optimization unstable: the optimal action distributions are task-dependent, unknown a priori, and often lead to oscillatory or inefficient control. To address this, we introduce the Residual-Action World Model (ResWM), a new framework that reformulates the control variable from absolute actions to residual actions -- incremental adjustments relative to the previous step. This design aligns with the inherent smoothness of real-world control, reduces the effective search space, and stabilizes long-horizon planning. To further strengthen the representation, we propose an Observation Difference Encoder that explicitly models the changes between adjacent frames, yielding compact latent dynamics that are naturally coupled with residual actions. ResWM is integrated into a Dreamer-style latent dynamics model with minimal modifications and no extra hyperparameters. Both imagination rollouts and policy optimization are conducted in the residual-action space, enabling smoother exploration, lower control variance, and more reliable planning. Empirical results on the DeepMind Control Suite demonstrate that ResWM achieves consistent improvements in sample efficiency, asymptotic returns, and control smoothness, significantly surpassing strong baselines such as Dreamer and TD-MPC. Beyond performance, ResWM produces more stable and energy-efficient action trajectories, a property critical for robotic systems deployed in real-world environments. These findings suggest that residual action modeling provides a simple yet powerful principle for bridging algorithmic advances in RL with the practical requirements of robotics.
Figures & tables
| Task | pixel SAC | +ResWM | DeepMDP | +ResWM | RAD | +ResWM | DeepRAD | +ResWM |
| 100K Step Scores | ||||||||
| Cartpole, Swingup | 237 49 | 476 42 | 389 44 | 526 59 | 694 28 | 813 36 | 703 32 | 845 67 |
| Reacher, Easy | 239 183 | 489 152 | 471 173 | 596 132 | 734 87 | 894 32 | 792 77 | 942 43 |
| Cheetah, Run | 118 13 | 314 17 | 306 25 | 413 29 | 364 38 | 498 49 | 453 39 | 542 64 |
| Walker, Walk | 95 19 | 386 26 | 384 197 | 572 68 | 552 87 | 714 57 | 582 91 | 694 87 |
| Finger, Spin | 230 194 | 493 112 | 509 72 | 706 113 | 813 65 | 928 86 | 832 101 | 986 86 |
| 100K STEP SCORES | CURL ( Srinivas et al., 2020 ) (ICML’20) | SVEA ( Hansen et al., 2021 ) (NeurIPS’21) | PlayVirtual ( Yu et al., 2021 ) (NeurIPS’21) | MLR ( Yu et al., 2022 ) (NeurIPS’22) | PSRL ( Choi et al., 2023 ) (CVPR’23) | TACO ( Zheng et al., 2024 ) (NeurIPS’23) | MaDi ( Grooten et al., 2023 ) (AAMAS’24) | ResAct ( Anonymous, 2025 ) (AAAI’25) | ResWM (Ours) |
| Cartpole, Swingup | 582 146 | 727 86 | 816 36 | 806 48 | 849 63 | 782 51 | 704 54 | 819 44 | 845 67 |
| Reacher, Easy | 538 233 | 811 115 | 785 142 | 866 103 | 621 202 | 821 97 | 766 101 | 917 59 | 942 42 |
| Cheetah, Run | 299 48 | 375 54 | 474 50 | 482 38 | 398 71 | 402 62 | 432 44 | 503 42 | 542 64 |
| Walker, Walk | 403 24 | 747 65 | 460 173 | 643 114 | 595 104 | 601 103 | 574 94 | 772 65 | 694 87 |
| Finger, Spin | 767 56 | 859 77 | 915 49 | 907 58 | 882 132 | 876 67 | 810 95 | 974 42 | 986 8 |
| Ball in cup, Catch | 769 43 | 915 71 | 929 31 | 933 16 | 922 60 | 902 54 | 884 36 | 948 44 | 963 26 |
| Task | Flare ( Shang et al., 2021 ) | TACO | MaDi | DeepRAD | ResAct | ResWM (500K) | Flare | TACO | MaDi | DeepRAD | ResAct | ResWM (1M) |
| Quadruped, Walk | 296 139 | 345 89 | 277 92 | 307 142 | 385 81 | 408 136 | 488 221 | 665 144 | 621 172 | 586 193 | 690 128 | 715 108 |
| Pendulum, Swingup | 242 152 | 485 167 | 372 101 | 308 137 | 618 380 | 645 112 | 809 31 | 784 42 | 751 41 | 626 220 | 817 6 | 836 36 |
| Hopper, Hop | 90 55 | 112 42 | 80 24 | 51 19 | 99 49 | 116 32 | 217 59 | 221 45 | 201 43 | 212 13 | 233 32 | 246 48 |
| Finger, Turn hard | 282 67 | 372 174 | 311 143 | 173 195 | 465 153 | 513 124 | 661 315 | 672 167 | 695 133 | 310 278 | 857 80 | 843 134 |
| Walker, Run | 426 33 | 355 89 | 382 87 | 375 177 | 467 27 | 496 62 | 556 93 | 582 63 | 562 68 | 508 125 | 554 21 | 584 57 |
| Average | 267.2 | 333.8 | 284.4 | 242.8 | 406.8 | 435.6 | 546.2 | 584.8 | 566.0 | 448.4 | 630.2 | 644.8 |
| Game | Random | Human | Flare | CURL | DeepMDP | MaDi | DeepRAD | TACO | ResAct | ResWM |
| Assault | 222.4 | 742 | 846 | 967 | 1264 | 1427 | 1824 | 1963 | 2164 | 2408 |
| BeamRider | 363.9 | 16926.5 | 1462 | 1824 | 1996 | 2172 | 2936 | 2542 | 3524 | 3928 |
| Berzerk | 123.7 | 2630.4 | 452 | 397 | 542 | 567 | 642 | 723 | 653 | 674 |
| Carnival | 0 | 3800 | 1876 | 2043 | 2467 | 2537 | 2896 | 3457 | 4203 | 4752 |
| Centipede | 2090.9 | 12017 | 3246 | 3721 | 3526 | 4386 | 4673 | 4726 | 5082 | 5431 |
| ChopperCommand | 811 | 7387.8 | 463 | 1579 | 1628 | 2136 | 3436 | 2962 | 3362 | 3528 |
Model-Based RL
Model-based reinforcement learning uses environment models to plan actions and learn policies with fewer real-world interactions.
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