Optimization-Guided Diffusion for Interactive Scene Generation
Pith reviewed 2026-05-17 00:30 UTC · model grok-4.3
The pith
Guided optimization during diffusion raises valid driving scenes from 32% to 72%
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
OMEGA re-anchors each reverse diffusion step via constrained optimization, steering the generation towards physically plausible and behaviorally coherent trajectories. Building on this framework, ego-attacker interactions are formulated as a game-theoretic optimization in the distribution space, approximating Nash equilibria to generate realistic, safety-critical adversarial scenarios.
What carries the argument
re-anchoring each reverse diffusion step via constrained optimization to enforce structural consistency and interaction awareness
Load-bearing premise
The constrained optimization problem solved at each diffusion step can be solved accurately and efficiently without distorting the underlying diffusion trajectory or introducing new inconsistencies.
What would settle it
Run the same generation pipeline with and without the per-step optimization on a fixed set of prompts; if the fraction of scenes passing physical and behavioral checks shows no substantial increase or introduces visible artifacts, the guidance mechanism fails to deliver the claimed improvement.
Figures
read the original abstract
Realistic and diverse multi-agent driving scenes are crucial for evaluating autonomous vehicles, but safety-critical events which are essential for this task are rare and underrepresented in driving datasets. Data-driven scene generation offers a low-cost alternative by synthesizing complex traffic behaviors from existing driving logs. However, existing models often lack controllability or yield samples that violate physical or social constraints, limiting their usability. We present OMEGA, an optimization-guided, training-free framework that enforces structural consistency and interaction awareness during diffusion-based sampling from a scene generation model. OMEGA re-anchors each reverse diffusion step via constrained optimization, steering the generation towards physically plausible and behaviorally coherent trajectories. Building on this framework, we formulate ego-attacker interactions as a game-theoretic optimization in the distribution space, approximating Nash equilibria to generate realistic, safety-critical adversarial scenarios. Experiments on nuPlan and Waymo show that OMEGA improves generation realism, consistency, and controllability, increasing the ratio of physically and behaviorally valid scenes from 32.35% to 72.27% for free exploration capabilities, and from 11% to 80% for controllability-focused generation. Our approach can also generate $5\times$ more near-collision frames with a time-to-collision under three seconds while maintaining the overall scene realism.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript introduces OMEGA, a training-free optimization-guided diffusion framework for generating realistic multi-agent driving scenes. It re-anchors each reverse diffusion step by solving a constrained optimization problem to enforce physical and interaction constraints, and extends the approach to a game-theoretic formulation for approximating Nash equilibria in ego-attacker interactions. Experiments on nuPlan and Waymo report increasing the ratio of physically and behaviorally valid scenes from 32.35% to 72.27% for free exploration and from 11% to 80% for controllability-focused generation, along with generating 5× more near-collision frames (time-to-collision under three seconds) while preserving overall scene realism.
Significance. If the central claims hold, this work offers a practical training-free method to steer diffusion-based scene generators toward higher physical and behavioral validity, which is valuable for synthesizing diverse safety-critical scenarios needed for autonomous vehicle evaluation. The approach builds on standard public datasets and standard validity checks without introducing free parameters or ad-hoc axioms.
major comments (2)
- [§3.2] §3.2 (re-anchoring procedure): The manuscript provides no convergence analysis, solver tolerance study, or ablation on update magnitude for the constrained optimization solved at each reverse diffusion step. Without this, it is unclear whether the reported validity gains (32.35%→72.27% and 11%→80%) arise from faithful steering consistent with the score function or from the optimization projecting samples into regions where the downstream metrics are easier to satisfy.
- [§4.2] §4.2 and Table 2 (experimental results): The validity ratios and 5× near-collision increase are presented without statistical significance tests, run-to-run variance, or an explicit ablation isolating the effect of the per-step optimization from other implementation choices (e.g., baseline diffusion sampler, constraint weighting). This information is load-bearing for confirming that the improvements are robust and attributable to the proposed method.
minor comments (2)
- [Abstract] Abstract: The precise definition of 'physically and behaviorally valid scenes' and the exact number of generated scenes used to compute the reported percentages should be stated for reproducibility.
- [Figure 4] Figure 4 (qualitative examples): Captions should explicitly label which rows correspond to free-exploration versus controllability-focused settings and which scenes are produced by OMEGA versus baselines.
Simulated Author's Rebuttal
We thank the referee for the constructive and detailed comments. We address each major comment below and describe the revisions we will make to strengthen the manuscript.
read point-by-point responses
-
Referee: [§3.2] §3.2 (re-anchoring procedure): The manuscript provides no convergence analysis, solver tolerance study, or ablation on update magnitude for the constrained optimization solved at each reverse diffusion step. Without this, it is unclear whether the reported validity gains (32.35%→72.27% and 11%→80%) arise from faithful steering consistent with the score function or from the optimization projecting samples into regions where the downstream metrics are easier to satisfy.
Authors: We thank the referee for this observation. The re-anchoring step solves a constrained quadratic program that minimizes Euclidean distance to the diffusion-predicted mean while enforcing the physical and interaction constraints; this formulation is intended to keep the update local and consistent with the score function. In the revised manuscript we will add: (i) convergence plots of the optimization residual across representative diffusion timesteps, (ii) an ablation varying solver tolerance (e.g., 10^{-3} vs. 10^{-4}) and maximum update magnitude, and (iii) a direct comparison of validity metrics obtained with and without the projection step. These additions will demonstrate that the reported gains arise from constraint enforcement within the diffusion manifold rather than from metric exploitation. revision: yes
-
Referee: [§4.2] §4.2 and Table 2 (experimental results): The validity ratios and 5× near-collision increase are presented without statistical significance tests, run-to-run variance, or an explicit ablation isolating the effect of the per-step optimization from other implementation choices (e.g., baseline diffusion sampler, constraint weighting). This information is load-bearing for confirming that the improvements are robust and attributable to the proposed method.
Authors: We agree that statistical rigor and targeted ablations are required. In the revision we will: (i) report all metrics as mean ± standard deviation over at least five independent random seeds, (ii) include paired statistical tests (e.g., Wilcoxon signed-rank) with p-values for the key improvements, and (iii) add an explicit ablation that isolates the per-step optimization by comparing the full OMEGA pipeline against variants that apply optimization only at the final step or with uniform constraint weights. These changes will confirm both robustness and the specific contribution of the proposed method. revision: yes
Circularity Check
No significant circularity; performance gains validated externally
full rationale
The paper describes OMEGA as a training-free method that applies constrained optimization at each reverse diffusion step to enforce physical and interaction constraints on a pre-trained scene generation model. The reported improvements (32.35% to 72.27% valid scenes for free exploration, 11% to 80% for controllability, and 5× more near-collision frames) are computed on external public datasets (nuPlan, Waymo) using standard validity metrics for collisions, trajectories, and interactions. These metrics are not defined in terms of the optimization variables or any fitted parameters internal to OMEGA. No self-definitional equations, fitted-input predictions, load-bearing self-citations, or ansatz smuggling appear in the abstract or described framework. The derivation chain remains independent of its evaluation outputs and is directly falsifiable against the cited benchmarks.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Reverse diffusion steps can be re-anchored by solving a constrained optimization problem while preserving the overall generative distribution.
Reference graph
Works this paper leans on
-
[1]
nuScenes: A multimodal dataset for autonomous driving
Holger Caesar, Varun Bankiti, Alex H Lang, Sourabh Vora, Venice Erin Liong, Qiang Xu, Anush Krishnan, Yu Pan, Gi- ancarlo Baldan, and Oscar Beijbom. nuScenes: A multimodal dataset for autonomous driving. InCVPR, 2020. 2
work page 2020
-
[2]
NuPlan: A closed-loop ML-based planning benchmark for autonomous vehicles
Holger Caesar, Juraj Kabzan, Kok Seang Tan, Whye Kit Fong, Eric Wolff, Alex Lang, Luke Fletcher, Oscar Beijbom, and Sammy Omari. nuPlan: A closed-loop ml-based plan- ning benchmark for autonomous vehicles.arXiv preprint arXiv:2106.11810, 2021. 7, 14
work page internal anchor Pith review Pith/arXiv arXiv 2021
-
[3]
Pseudo- simulation for autonomous driving
Wei Cao, Marcel Hallgarten, Tianyu Li, Daniel Dauner, Xunjiang Gu, Caojun Wang, Yakov Miron, Marco Aiello, Hongyang Li, Igor Gilitschenski, Boris Ivanovic, Marco Pavone, Andreas Geiger, and Kashyap Chitta. Pseudo- simulation for autonomous driving. InCoRL, 2025. 2
work page 2025
-
[4]
End-to-end autonomous driving: Challenges and frontiers.IEEE TPAMI, 2024
Li Chen, Penghao Wu, Kashyap Chitta, Bernhard Jaeger, Andreas Geiger, and Hongyang Li. End-to-end autonomous driving: Challenges and frontiers.IEEE TPAMI, 2024. 3
work page 2024
-
[5]
Cheng Chi, Zhenjia Xu, Siyuan Feng, Eric Cousineau, Yilun Du, Benjamin Burchfiel, Russ Tedrake, and Shuran Song. Diffusion policy: Visuomotor policy learning via action dif- fusion.The International Journal of Robotics Research, 44 (10-11):1684–1704, 2025. 7, 18, 20
work page 2025
-
[6]
SLEDGE: Synthesizing driving environments with genera- tive models and rule-based traffic
Kashyap Chitta, Daniel Dauner, and Andreas Geiger. SLEDGE: Synthesizing driving environments with genera- tive models and rule-based traffic. InECCV, 2024. 3
work page 2024
-
[7]
Diffusion Posterior Sampling for General Noisy Inverse Problems
Hyungjin Chung, Jeongsol Kim, Michael T Mccann, Marc L Klasky, and Jong Chul Ye. Diffusion posterior sam- pling for general noisy inverse problems.arXiv preprint arXiv:2209.14687, 2022. 3
work page internal anchor Pith review Pith/arXiv arXiv 2022
-
[8]
NA VSIM: Data-driven non-reactive autonomous vehicle simulation and benchmark- ing
Daniel Dauner, Marcel Hallgarten, Tianyu Li, Xinshuo Weng, Zhiyu Huang, Zetong Yang, Hongyang Li, Igor Gilitschenski, Boris Ivanovic, Marco Pavone, et al. NA VSIM: Data-driven non-reactive autonomous vehicle simulation and benchmark- ing. InNeurIPS Datasets and Benchmarks, 2024. 2
work page 2024
-
[9]
Diffusion models beat gans on image synthesis
Prafulla Dhariwal and Alexander Nichol. Diffusion models beat gans on image synthesis. InNeurIPS, 2021. 3
work page 2021
-
[10]
CARLA: An open urban driving simulator
Alexey Dosovitskiy, German Ros, Felipe Codevilla, Antonio Lopez, and Vladlen Koltun. CARLA: An open urban driving simulator. InCoRL, 2017. 2
work page 2017
-
[11]
Large scale interactive mo- tion forecasting for autonomous driving: The waymo open motion dataset
Scott Ettinger, Shuyang Cheng, Benjamin Caine, Chenxi Liu, Hang Zhao, Sabeek Pradhan, Yuning Chai, Ben Sapp, Charles R Qi, Yin Zhou, et al. Large scale interactive mo- tion forecasting for autonomous driving: The waymo open motion dataset. InICCV, 2021. 8
work page 2021
-
[12]
Lan Feng, Quanyi Li, Zhenghao Peng, Shuhan Tan, and Bolei Zhou. TrafficGen: Learning to generate diverse and realistic traffic scenarios.arXiv preprint arXiv:2210.06609, 2022. 2
-
[13]
Shuo Feng, Haowei Sun, Xintao Yan, Haojie Zhu, Zhengxia Zou, Shengyin Shen, and Henry X Liu. Dense reinforcement learning for safety validation of autonomous vehicles.Nature, 615(7953):620–627, 2023. 3
work page 2023
-
[14]
Introduction to sensitivity and stability analysis in non linear programming
Anthony V Fiacco. Introduction to sensitivity and stability analysis in non linear programming. 1983. 2
work page 1983
-
[15]
King: Generating safety-critical driving scenarios for robust imitation via kine- matics gradients
Niklas Hanselmann, Katrin Renz, Kashyap Chitta, Apra- tim Bhattacharyya, and Andreas Geiger. King: Generating safety-critical driving scenarios for robust imitation via kine- matics gradients. InECCV, 2022. 3
work page 2022
-
[16]
Denoising diffu- sion probabilistic models
Jonathan Ho, Ajay Jain, and Pieter Abbeel. Denoising diffu- sion probabilistic models. InNeurIPS, 2020. 3
work page 2020
-
[17]
Planning-oriented autonomous driving
Yihan Hu, Jiazhi Yang, Li Chen, Keyu Li, Chonghao Sima, Xizhou Zhu, Siqi Chai, Senyao Du, Tianwei Lin, et al. Planning-oriented autonomous driving. InCVPR, 2023. 3
work page 2023
-
[18]
Solv- ing motion planning tasks with a scalable generative model
Yihan Hu, Siqi Chai, Zhening Yang, Jingyu Qian, Kun Li, Wenxin Shao, Haichao Zhang, Wei Xu, and Qiang Liu. Solv- ing motion planning tasks with a scalable generative model. InECCV, 2024. 2, 3
work page 2024
-
[19]
Zhiyu Huang, Zixu Zhang, Ameya Vaidya, Yuxiao Chen, Chen Lv, and Jaime Fern ´andez Fisac. Versatile scene- consistent traffic scenario generation as optimization with diffusion.arXiv preprint arXiv:2404.02524, 2024. 2
-
[20]
MotionDiffuser: Con- trollable multi-agent motion prediction using diffusion
Chiyu Jiang, Andre Cornman, Cheolho Park, Benjamin Sapp, Yin Zhou, Dragomir Anguelov, et al. MotionDiffuser: Con- trollable multi-agent motion prediction using diffusion. In CVPR, 2023. 2
work page 2023
-
[21]
SceneDiffuser: Ef- ficient and controllable driving simulation initialization and rollout
Max Jiang, Yijing Bai, Andre Cornman, Christopher Davis, Xiukun Huang, Hong Jeon, Sakshum Kulshrestha, John Lam- bert, Shuangyu Li, Xuanyu Zhou, et al. SceneDiffuser: Ef- ficient and controllable driving simulation initialization and rollout. InNeurIPS, 2024. 2, 3, 7, 8, 18, 20 9
work page 2024
-
[22]
Mtgs: Multi-traversal gaussian splatting.arXiv preprint arXiv:2503.12552, 2025
Tianyu Li, Yihang Qiu, Zhenhua Wu, Carl Lind- str¨om, Peng Su, Matthias Nießner, and Hongyang Li. Mtgs: Multi-traversal gaussian splatting.arXiv preprint arXiv:2503.12552, 2025. 2
-
[23]
Model-based policy adaptation for closed-loop end-to-end autonomous driving
Haohong Lin, Yunzhi Zhang, Wenhao Ding, Jiajun Wu, and Ding Zhao. Model-based policy adaptation for closed-loop end-to-end autonomous driving. InNeurIPS, 2025. 2
work page 2025
-
[24]
Haochen Liu, Tianyu Li, Haohan Yang, Li Chen, Caojun Wang, Ke Guo, Haochen Tian, Hongchen Li, Hongyang Li, and Chen Lv. Reinforced refinement with self-aware ex- pansion for end-to-end autonomous driving.arXiv preprint arXiv:2506.09800, 2025. 3
-
[25]
Curse of rarity for autonomous vehicles.Nature communications, 15(1):4808, 2024
Henry X Liu and Shuo Feng. Curse of rarity for autonomous vehicles.Nature communications, 15(1):4808, 2024. 2
work page 2024
-
[26]
Microscopic traffic simulation using sumo
Pablo Alvarez Lopez, Michael Behrisch, Laura Bieker-Walz, Jakob Erdmann, Yun-Pang Fl¨otter¨od, Robert Hilbrich, Leon- hard L¨ ucken, Johannes Rummel, Peter Wagner, and Evamarie Wießner. Microscopic traffic simulation using sumo. InITSC,
-
[27]
SceneControl: Diffusion for controllable traffic scene generation
Jack Lu, Kelvin Wong, Chris Zhang, Simon Suo, and Raquel Urtasun. SceneControl: Diffusion for controllable traffic scene generation. InICRA, 2024. 17
work page 2024
-
[28]
Unleashing generalization of end-to-end au- tonomous driving with controllable long video generation
Enhui Ma, Lijun Zhou, Tao Tang, Zhan Zhang, Dong Han, Junpeng Jiang, Kun Zhan, Peng Jia, Xianpeng Lang, Haiyang Sun, et al. Unleashing generalization of end-to-end au- tonomous driving with controllable long video generation. arXiv preprint arXiv:2406.01349, 2024. 2
-
[29]
Scenario dreamer: Vector- ized latent diffusion for generating driving simulation envi- ronments
Luke Rowe, Roger Girgis, Anthony Gosselin, Liam Paull, Christopher Pal, and Felix Heide. Scenario dreamer: Vector- ized latent diffusion for generating driving simulation envi- ronments. InCVPR, 2025. 17
work page 2025
-
[30]
MotionLM: Multi-agent motion forecasting as language modeling
Ari Seff, Brian Cera, Dian Chen, Mason Ng, Aurick Zhou, Nigamaa Nayakanti, Khaled S Refaat, Rami Al-Rfou, and Benjamin Sapp. MotionLM: Multi-agent motion forecasting as language modeling. InICCV, 2023. 2, 3
work page 2023
-
[31]
Deep unsupervised learning using nonequilibrium thermodynamics
Jascha Sohl-Dickstein, Eric Weiss, Niru Maheswaranathan, and Surya Ganguli. Deep unsupervised learning using nonequilibrium thermodynamics. InICML, 2015. 3
work page 2015
-
[32]
Denoising diffusion implicit models
Jiaming Song, Chenlin Meng, and Stefano Ermon. Denoising diffusion implicit models. InICLR, 2021. 3
work page 2021
-
[33]
Riccardo Spica, Eric Cristofalo, Zijian Wang, Eduardo Mon- tijano, and Mac Schwager. A real-time game theoretic planner for autonomous two-player drone racing.IEEE Transactions on Robotics, 36(5):1389–1403, 2020. 2, 6, 12
work page 2020
-
[34]
SceneDiffuser++: City-scale traffic simulation via a generative world model
Shuhan Tan, John Lambert, Hong Jeon, Sakshum Kul- shrestha, Yijing Bai, Jing Luo, Dragomir Anguelov, Mingx- ing Tan, and Chiyu Max Jiang. SceneDiffuser++: City-scale traffic simulation via a generative world model. InCVPR,
-
[35]
SimScale: Learning to Drive via Real-World Simulation at Scale
Haochen Tian, Tianyu Li, Haochen Liu, Jiazhi Yang, Yihang Qiu, Guang Li, Junli Wang, Yinfeng Gao, Zhang Zhang, Liang Wang, Hangjun Ye, Tieniu Tan, Long Chen, and Hongyang Li. Simscale: Learning to drive via real-world simulation at scale.arXiv preprint arXiv:2511.23369, 2025. 2
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[36]
AdvSim: Generating safety-critical scenarios for self- driving vehicles
Jingkang Wang, Ava Pun, James Tu, Sivabalan Manivasagam, Abbas Sadat, Sergio Casas, Mengye Ren, and Raquel Urta- sun. AdvSim: Generating safety-critical scenarios for self- driving vehicles. InCVPR, 2021. 3
work page 2021
-
[37]
Advdiffuser: Generating adversarial safety-critical driving scenarios via guided diffusion
Yuting Xie, Xianda Guo, Cong Wang, Kunhua Liu, and Long Chen. Advdiffuser: Generating adversarial safety-critical driving scenarios via guided diffusion. InIROS. 2, 3
-
[38]
DiffScene: Diffusion-based safety-critical scenario genera- tion for autonomous vehicles
Chejian Xu, Aleksandr Petiushko, Ding Zhao, and Bo Li. DiffScene: Diffusion-based safety-critical scenario genera- tion for autonomous vehicles. InAAAI, 2025. 2
work page 2025
-
[39]
Resim: Reliable world simulation for autonomous driving
Jiazhi Yang, Kashyap Chitta, Shenyuan Gao, Long Chen, Yuqian Shao, Xiaosong Jia, Hongyang Li, Andreas Geiger, Xiangyu Yue, and Li Chen. Resim: Reliable world simulation for autonomous driving. 2025. 2
work page 2025
-
[40]
CAT: Closed-loop adversarial training for safe end-to-end driving
Linrui Zhang, Zhenghao Peng, Quanyi Li, and Bolei Zhou. CAT: Closed-loop adversarial training for safe end-to-end driving. InCoRL, 2023. 3, 18
work page 2023
-
[41]
Diffusion-based planning for autonomous driving with flexi- ble guidance
Yinan Zheng, Ruiming Liang, Kexin ZHENG, Jinliang Zheng, Liyuan Mao, Jianxiong Li, Weihao Gu, Rui Ai, Shengbo Eben Li, Xianyuan Zhan, and Jingjing Liu. Diffusion-based planning for autonomous driving with flexi- ble guidance. InICLR, 2025. 3, 8, 20
work page 2025
-
[42]
Ziyuan Zhong, Davis Rempe, Danfei Xu, Yuxiao Chen, Sushant Veer, Tong Che, Baishakhi Ray, and Marco Pavone. Guided conditional diffusion for controllable traffic simula- tion.arXiv preprint arXiv:2210.17366, 2022. 2, 3, 8, 18, 20
-
[43]
Decoupled diffusion sparks adap- tive scene generation
Yunsong Zhou, Naisheng Ye, William Ljungbergh, Tianyu Li, Jiazhi Yang, Zetong Yang, Hongzi Zhu, Christoffer Pe- tersson, and Hongyang Li. Decoupled diffusion sparks adap- tive scene generation. InICCV, 2025. 2, 3, 7, 8, 14, 18, 20 10 Optimization-Guided Diffusion for Interactive Scene Generation Supplementary Material A. Theoretical Foundations A.1. Deriv...
work page 2025
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.