Recognition: no theorem link
Simulation-Ready Cluttered Scene Estimation via Physics-aware Joint Shape and Pose Optimization
Pith reviewed 2026-05-15 20:13 UTC · model grok-4.3
The pith
A joint optimization framework recovers shapes and poses of multiple objects in cluttered scenes while enforcing physical validity for direct use in simulators.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The paper claims that by using a shape-differentiable contact model and deriving an efficient solver from the structured sparsity of the augmented Lagrangian Hessian, it is possible to jointly optimize the shapes and poses of multiple rigid objects under physical constraints, yielding physically valid and simulation-ready scene reconstructions from real-world observations.
What carries the argument
The shape-differentiable contact model, which enables gradient-based optimization over both object shapes and poses by providing differentiable contact forces and geometries.
Load-bearing premise
The shape-differentiable contact model must remain globally differentiable and the augmented Lagrangian solver must converge without getting stuck in local minima when optimizing shapes and poses together in multi-object contact scenarios.
What would settle it
A test scene with five or more objects where the optimization produces interpenetrating shapes or fails to converge to a physically stable configuration, or where the simulated behavior of the reconstructed scene does not match the observed real-world motion.
Figures
read the original abstract
Estimating simulation-ready scenes from real-world observations is crucial for downstream planning and policy learning tasks. Regretfully, existing methods struggle in cluttered environments, often exhibiting prohibitive computational cost, poor robustness, and restricted generality when scaling to multiple interacting objects. We propose a unified optimization-based formulation for real-to-sim scene estimation that jointly recovers the shapes and poses of multiple rigid objects under physical constraints. Our method is built on two key technical innovations. First, we leverage the recently introduced shape-differentiable contact model, whose global differentiability permits joint optimization over object geometry and pose while modeling inter-object contacts. Second, we exploit the structured sparsity of the augmented Lagrangian Hessian to derive an efficient linear system solver whose computational cost scales favorably with scene complexity. Building on this formulation, we develop an end-to-end Simulation-ready Physics-Aware Reconstruction for Cluttered Scenes (SPARCS) pipeline, which integrates learning-based object initialization, physics-constrained joint shape-pose optimization, and differentiable texture refinement. Experiments on cluttered scenes with up to 5 objects and 22 convex hulls demonstrate that our approach robustly reconstructs physically valid, simulation-ready object shapes and poses. Project webpage: https://rory-weicheng.github.io/SPARCS/.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces SPARCS, a unified optimization pipeline for real-to-sim scene estimation that jointly recovers shapes and poses of multiple rigid objects under physical contact constraints. It builds on a shape-differentiable contact model and exploits structured sparsity in the augmented Lagrangian Hessian for an efficient linear solver. The pipeline combines learning-based initialization, physics-constrained joint optimization, and differentiable texture refinement. Experiments on cluttered scenes with up to 5 objects and 22 convex hulls are claimed to produce physically valid, simulation-ready reconstructions.
Significance. If the central claims hold under quantitative scrutiny, the work would advance robotics by enabling scalable, physics-consistent scene reconstruction from real observations, directly supporting downstream planning and policy learning. The combination of differentiable contact modeling with an efficient sparse solver addresses a practical bottleneck in multi-object optimization. The absence of metrics, baselines, and convergence validation in the current manuscript, however, limits assessment of whether these innovations deliver reliable gains over existing approaches.
major comments (2)
- [Experiments] Experiments section: The claim that the method 'robustly reconstructs physically valid, simulation-ready object shapes and poses' rests entirely on qualitative demonstrations for scenes with up to 5 objects. No quantitative metrics (pose error, penetration depth, contact violation volume, or success rate across random initializations), baseline comparisons, or ablation studies on augmented Lagrangian convergence (iteration counts, failure rates, sensitivity to initialization) are reported. This directly undermines evaluation of the central robustness claim in multi-contact settings.
- [Method] Optimization formulation (around the augmented Lagrangian solver): The manuscript assumes the shape-differentiable contact model remains globally differentiable and that the solver converges reliably without local minima when shapes and poses are optimized jointly. No empirical checks (gradient accuracy tests, penetration metrics over random seeds, or multi-contact failure analysis) are supplied to support this assumption for scenes with up to 22 convex hulls.
minor comments (1)
- [Abstract] The abstract and introduction would benefit from a brief statement of the specific quantitative improvements (if any) over prior art, rather than relying solely on the qualitative claim.
Simulated Author's Rebuttal
We thank the referee for the constructive feedback on our manuscript. We address each major comment below and will revise the manuscript to incorporate additional quantitative evaluations and empirical validations as outlined.
read point-by-point responses
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Referee: [Experiments] Experiments section: The claim that the method 'robustly reconstructs physically valid, simulation-ready object shapes and poses' rests entirely on qualitative demonstrations for scenes with up to 5 objects. No quantitative metrics (pose error, penetration depth, contact violation volume, or success rate across random initializations), baseline comparisons, or ablation studies on augmented Lagrangian convergence (iteration counts, failure rates, sensitivity to initialization) are reported. This directly undermines evaluation of the central robustness claim in multi-contact settings.
Authors: We agree that quantitative metrics, baseline comparisons, and ablation studies are necessary to fully substantiate the robustness claims. The current experiments prioritize qualitative demonstrations to highlight the pipeline's ability to produce physically valid, simulation-ready reconstructions in cluttered multi-object scenes. In the revised manuscript, we will add quantitative metrics including pose errors, penetration depths, contact violation volumes, and success rates over random initializations. We will also include comparisons to relevant baselines and ablations on the augmented Lagrangian solver, reporting iteration counts, failure rates, and sensitivity to initialization. revision: yes
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Referee: [Method] Optimization formulation (around the augmented Lagrangian solver): The manuscript assumes the shape-differentiable contact model remains globally differentiable and that the solver converges reliably without local minima when shapes and poses are optimized jointly. No empirical checks (gradient accuracy tests, penetration metrics over random seeds, or multi-contact failure analysis) are supplied to support this assumption for scenes with up to 22 convex hulls.
Authors: The shape-differentiable contact model is globally differentiable by construction, as established in the referenced prior work on which it builds. For the augmented Lagrangian solver, we will strengthen the manuscript by adding the requested empirical checks. In the revision, we will report gradient accuracy tests, penetration metrics across random seeds, and multi-contact failure analysis to validate reliable convergence in scenes with up to 22 convex hulls. revision: yes
Circularity Check
No significant circularity; formulation builds on external contact model and derives solver independently
full rationale
The paper introduces a joint shape-pose optimization pipeline (SPARCS) that leverages an externally introduced shape-differentiable contact model and exploits structured sparsity in the augmented Lagrangian Hessian to derive an efficient solver. No load-bearing step reduces by construction to a fitted parameter, self-definition, or self-citation chain. The central claim of robust reconstruction in cluttered scenes is supported by experiments rather than tautological predictions. The derivation chain remains self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
free parameters (1)
- optimization weights and contact stiffness
axioms (2)
- domain assumption Objects behave as rigid bodies whose geometry can be represented by convex hulls
- domain assumption The shape-differentiable contact model provides accurate gradients for simultaneous shape and pose updates
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Force equilibrium for objects: Cequi(z)≜¯C(z)=∇q ⎡⎢⎢⎢⎢⎣ Ψ(q, x)−∑ i≠i′ ∑ j,j′ ∑ k ⟨Xijk, f∥ ijk,i′j′⟩ ⎤⎥⎥⎥⎥⎦ =0,
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Orthogonality: C iji′j′ orth (z)≜ ⎛ ⎜⎜ ⎝ ⋮ ⟨f⊥ ijk,i′j′, f ∥ ijk,i′j′⟩ ⋮ ⎞ ⎟⎟ ⎠ =0,
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Friction cone: C iji′j′ cone (z)≜ ⎛ ⎜ ⎝ ⋮ ∥f∥ ijk,i′j′∥−η∥f⊥ ijk,i′j′∥ ⋮ ⎞ ⎟ ⎠ ≤0,
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Tangential force equilibrium for separating plane: Ciji′j′ plane(z)≜⎛ ⎝ ∑kf∥ ijk,i′j′+∑k′f∥ i′j′k′,ij Tiji′j′[∑kXijk×f∥ ijk,i′j′+∑k′Xi′j′k′×f∥ i′j′k′,ij] ⎞ ⎠=0. Note that we redefine ¯CasC equi for more conveniently dis- tinguishing different types of constraints. We then compactly group the constraints as follows: Ceq(z)≜ ⎛ ⎜⎜ ⎝ Cequi(z) {Ciji′j′ orth (z...
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[51]
Simulator Parameter Setting:For a complete list of simulator related parameters, we refer the readers to the official documentation. Here we explain the critical settings that differ from the default values: the simulatortimstep=10 −3, and theintegratoris set to “implicit” to enhance simulation stability for the cluttered scene. Moreover, MuJoCo’s contact...
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[52]
The results of these scene estimators are using mesh-based object representation
Baseline Processing:For comparison, we simulate the scene estimated using various visual inference pipelines, in- cluding the SAM3D + FoundationPose pipeline and two baselines below. The results of these scene estimators are using mesh-based object representation. For each of the estimated rigid bodies in the scene, we replace their collision mesh by a hi...
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[53]
Optimized Result Processing:We discuss details for loading results from our optimization result to MuJoCo. For each of the rigid bodies in the scene, it’s collision geometry is the unions of convex hulls extracted from the optimization resultx, while for visual geometry, we used the triangular mesh merged fromxusing Manifold3d Library [19] with the textur...
work page 1936
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