NeurIPS 2026 Papers

Conference on Neural Information Processing Systems

Decision breakdown

6,437papers

Counted from the official paper list; may differ slightly from the number the conference announced.

  • Oral
    991.5%
  • Spotlight
    2403.7%
  • Poster
    6,09894.7%

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Topic: Multimodal LLMs · 1,366 papers · Reset filters

A Principled Optimal Transport Framework for Frame Selection in Long Video Understanding

Ziwei Zhao, Yuhang Liu

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Long-video understanding with multimodal LLMs is fundamentally constrained by the mismatch between video length and the model's limited visual context budget, making frame selection essential for practical reasoning. Existing query-aware methods typically rely on heuristic pipelines: they assign one-dimensional query-conditioned scores to frames and then apply sampling, ranking, or extraction rules to form the final subset. While effective in practice, such methods are generally not derived from an explicit optimization objective and struggle to capture the heterogeneous evidence required for complex reasoning. In this paper, we revisit long-video frame selection from a principled optimization perspective. We formulate it as a structured evidence-allocation problem and propose OTFS, an optimal transport framework that maps multiple evidence sources onto video frames. To reflect the asymmetry of this problem---important evidence should be preserved, whereas redundant frames need not absorb mass---we instantiate this view with a semi-unbalanced entropic optimal transport objective and an efficient solver, OTFS-Sinkhorn. Combined with an exact dynamic program for coverage-aware subset extraction, OTFS yields a practical two-stage training-free pipeline. We further show that, in the single-source case, our formulation induces a Gibbs-type distribution over frames, making Q-Frame's temperature-scaled distribution a special case of our framework while also providing a broader perspective for understanding related prior methods. Experiments on three long-video understanding benchmarks show that OTFS consistently outperforms strong training-free baselines. Code will be released.

Poster
A Multimodal Benchmark for Evaluating Cause-of-Death Inference Using Child Health and Mortality Data

Junhe Yang, Soumyakanti Pan, Hyun Seung Lim, YUE CHU, Yuting Guo, Nishtha Agarwal, Varun Babbar, Gaurav Rajesh Parikh, Yiqun Chen, Chris A Rees, Ziyaad Dangor, Sanjay G Lala, Zehang Li, Samuel J Clark, Zhenke Wu, Abhirup Datta, Li Liu, Cynthia Rudin, Samuel Scarpino, Benjamin M Gyori, Tyler H. McCormick

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Accurately attributing causes of death is vital for global health, yet fewer than 5% of deaths in resource-constrained regions are medically certified. To assign causes to these unlabeled deaths at scale, practitioners traditionally rely on verbal autopsy, using supervised statistical models to classify based on structured survey data. However, modern mortality surveillance increasingly collects rich, unstructured multimodal data, such as free-text caregiver narratives and postmortem diagnostics, which traditional supervised statistical models struggle to seamlessly integrate. In this paper, we present a comprehensive, multimodal benchmark for cause-of-death classification using data from the Child Health and Mortality Prevention Surveillance (CHAMPS) network, a unique surveillance platform spanning nine countries across South Asia and Sub-Saharan Africa. Using this dataset, we introduce an evaluation framework designed to rigorously assess diagnostic reasoning, moving beyond traditional metrics that fail to capture complex clinical realities. We demonstrate the utility of this benchmark by evaluating zero-shot large language models against supervised baselines across various data modalities. Our results reveal distinct differences in how these modeling approaches synthesize unstructured medical evidence. This benchmark provide a rigorously defined resource for assessing clinical reasoning in next-generation mortality surveillance.

Poster
A Method-Class Divide in Sub-4-Bit Quantization:\\Iterative vs.\ Single-Pass Sensitivity to Data Composition

Yehong Jiang, Yen-Kuang Chen, Xinmin Tian

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Block-wise post-training quantization (PTQ) compresses LLMs by minimizing per-block reconstruction error on a small calibration set. We show that the \emph{composition} of this set (200 samples) is a targeted lever at extreme bit widths, acting only on iterative methods. In a controlled study spanning six data-dependent PTQ methods plus a data-free baseline, six models (1.7B--8B) across three families plus 70B verification, three bit widths, and a 10-task evaluation with four-seed replication, we find a sharp \textbf{near-cliff method-class divide}. In each method's pre-cliff regime (where the model retains predictive function), iterative methods (SignRound~V2, OmniQuant, AQLM) gain 0.74--1.93pp on the 10-task average from switching Pile to a fragility-guided dataset (FragCal-DC), while single-pass analytical methods (GPTQ, AWQ) show near-zero response ($|\Delta|{\le}0.30$pp). Both classes are evaluated on functional Pile baselines (0.42--0.61, well above chance); above the cliff, every method becomes data-composition-insensitive. A reconstruction-loss paradox (the method that most reduces its proxy loss gains nothing downstream, while the method that barely moves the proxy gains the most) sharpens the mechanism; fixed-reference held-out evaluation confirms the proxy--downstream disconnect. A wrong-answer contamination ablation retains 87--91\% of the improvement and a data-dependent single-pass control (RTN-opt) shows zero response, isolating the iterative optimization loop. A weight-space probe shows SignRound-V2 preserves higher per-group scale heterogeneity than GPTQ on 9 of 9 (model, width) cells; a scale-flatten knockout shows this heterogeneity is necessary for iterative fidelity. We release FragCal-DC, the discriminative-task instance used here, as a drop-in JSON for the evaluated setting.

Poster
A Mechanistic Interpretability Study of an Astronomical Foundation Model

Rachel Zhang, Alberto Bietti, Wes Gurnee, Alessandro Favero, Miles Cranmer

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Scientific foundation models trained on multimodal data are increasingly deployed across the sciences, but whether their internal computations correspond to known scientific operations or proceed through different mechanisms remains unclear. Understanding these mechanisms is essential for assessing reliability, identifying failure modes, and judging when predictions can be trusted in scientific workflows. We present the first mechanistic interpretability study of an astronomy foundation model, focused on AION-1's multimodal advantage in redshift prediction from broadband photometry and imaging over photometry alone. We find that this advantage concentrates on extended and dust-attenuated galaxies, with the gain localized by layerwise probing to AION-1's first encoder block. We examine two attention heads in this block and find that representation and function dissociate in opposite directions across them. The first head linearly encodes classical photometric features and organizes its image output along a radial gradient, yet ablation and activation patching show this structure has no measurable causal effect on the prediction. The second head shows no distinctive probe signature on the photometric-redshift estimation operations we tested, yet ablating it on dust-attenuated galaxies eliminates the multimodal advantage and amplifies the attenuation-bias signature beyond the photometry-only baseline, indicating that this head implements a correction for attenuation bias. Whether this reflects a methodological limitation in interpretability or an undiscovered astronomical empirical relation is itself an open question, and one that bears directly on using interpretability as a tool for scientific discovery.

Poster
A Mechanistic Analysis of Looped Reasoning Language Models

Hugh Blayney, Alvaro Arroyo, Johan Obando-Ceron, Pablo Samuel Castro, Aaron Courville, Michael Bronstein, Xiaowen Dong

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Reasoning has become a central capability in large language models. Recent research has shown that reasoning performance can be improved by looping an LLM’s layers in the latent dimension, resulting in looped reasoning language models. Despite promising results, few works have investigated how their internal dynamics differ from those of standard feedforward models. In this paper, we conduct a mechanistic analysis of latent states and layer behavior in looped language models, focusing in particular on how the stages of inference observed in feedforward models compare to those observed in looped ones. We analyze cyclic recurrence and show that for many of the studied models each layer in the cycle converges to a distinct fixed point; consequently, the recurrent block follows a consistent cyclic trajectory in the latent space. We provide evidence that as these fixed points are reached, attention-head behavior stabilizes, leading to constant behavior across recurrences. Empirically, we discover that recurrent blocks learn stages of inference that closely mirror those of feedforward models, repeating these stages in depth with each iteration. We study how architectural choices influence the emergence and stability of these cyclic fixed points and stages of inference, providing practical guidance for looped language model design.

Poster
A Latent World-Action Model with Jointly Aligned Reasoning

Hao Luo, Wanpeng Zhang, Yicheng Feng, Sipeng Zheng, Haiweng Xu, Chaoyi Xu, Ziheng Xi, Yuhui Fu, Zongqing Lu

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Despite recent progress, existing general robot policies, particularly Vision-Language-Action models, are still primarily trained to map observations directly to actions using sparse action supervision. As a result, they often learn shallow observation-to-action correlations instead of deeper representations of world dynamics, including object motion, physical interaction, and long-horizon task progression. Recent world-action models attempt to address this limitation through future-frame prediction, but pixel-space rollout is computationally expensive and poorly aligned with the abstractions required for control, forcing the model to reconstruct visual details irrelevant to action. We present Being-H0.7, a latent world-action model that introduces future-aware reasoning into VLA-style policies without generating future frames. Our model inserts learnable latent queries between perception and action, forming an explicit reasoning interface for action generation. To train this interface, we adopt a future-informed dual-branch design: a deployable prior branch infers latent states from the current context, while a training-only posterior branch replaces latent queries with embeddings from future frames. Joint alignment between the two branches enables the prior branch to learn predictive, action-relevant latent structure directly from current observations. Under a controlled training setup for comprehensive validation, Being-H0.7 achieves state-of-the-art or competitive performance across diverse benchmarks, while further demonstrating strong deployability on real-robot manipulation tasks.

Poster
A Graph Foundation Model for Unified Clustering

Renda Han, Xiaobao Wang, Longbiao Wang, Dayu Hu, Ronghao Fu, Di Jin

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Graph clustering is a fundamental task for understanding graph-structured data without labels, yet classical end-to-end methods require retraining on each dataset, limiting their generalization ability. Although Graph Foundation Models (GFMs) enable transferable learning across diverse graph tasks, they are not directly applicable to graph clustering. This limitation stems from two key factors: the inability to learn mutually beneficial knowledge on both the node and graph levels, and the lack of a completely unsupervised clustering-oriented design. To bridge this gap, we propose a **G**raph **F**oundation **M**odel for **U**nified **C**lustering (GFM-UC), which pre-trains on the source domain and only requires fine-tuning for fast clustering in the target domain. The entire learning process does not require any labels. Specifically, in the pre-training stage, we select learnable high-confidence unified subgraph prototypes from the source domain. And then we generalize them to train the clustering network collaboratively. In the fine-tuning stage, we align the target domain with the source domain in a distribution-aware manner to further refine the clustering head and obtain more well-separated cluster boundaries. Extensive experiments on five datasets demonstrate that our method significantly outperforms existing state-of-the-art approaches.

Spotlight
A General Concept-based Decomposition for Vision–Language Embeddings

Simone Alberto Peirone, Ortal Senouf, Francesca Pistilli, Giuseppe Averta, Pascal Frossard

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Vision-language models are designed to capture the compositional structure of the world through multi-modal alignment; however, it remains unclear whether their representations truly align with the way a human would naturally describe the same visual input. Prior works attempt to decompose visual embeddings into their concept-level contributions, but their instance-level optimization is inherently local and does not capture the model’s global semantic structure, which is essential for compositional generalization across different inputs, tasks and domains. We introduce GRACE, a method that learns this concept-based structure at the feature space level, producing semantic and general concept decompositions. To achieve this, we propose a novel training objective that preserves the geometric relations of different samples in the concept space, enabling a better understanding of how concepts compose and relate to each other. We validate GRACE on several image and video benchmarks, showing that its concept decomposition is aligned with human perception and achieves faithful decompositions across different tasks and domains. With minimal overhead, GRACE makes existing Vision-Language Models more interpretable, while preserving most of their original performance.

Poster
A Foundational Model System for Datacenter Machine Repairs

Yuanlin Wen, Elan S Markowitz, Zubo Gu, Sami Abu-El-Haija, Bryan Perozzi, Michael Galkin, Ali Parviz, Aayush Gupta, Venkata Chivukula, Griffin Hadfield, Aravind Akella, Daniel J Frame, Vahab Mirrokni, Amin Vahdat

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The rapid scale-up of AI infrastructure has made datacenter reliability a cornerstone of the cloud business economy. Hardware failures in hyper-scale AI clusters do not merely disrupt individual machines; they stall multi-million dollar training workloads, and so the downtime of individual machines can cause outsized economic losses. Minimizing machine downtime, therefore, is more important than ever. To address this, we present DrWatson, an AI-driven hardware diagnosis system that pioneers a foundation-model approach to automated datacenter maintenance. Deployed at production scale within a major AI hyperscaler, DrWatson yields substantial efficiency gains across diverse compute architectures. Real-world evaluations demonstrate that it reduces production downtime by 18.3% on GPU platforms and 16.1% on custom AI accelerators. Furthermore, it significantly accelerates hardware deployment, cutting quality assurance (QA) time by 28.3% for GPUs and 25.1% for custom accelerators. These results establish DrWatson as a field-tested solution for maximizing the reliability and cost efficiency of next generation AI fleets.

Poster
A Favorable Regime Between ODE and SDE for Few-Step Diffusion Sampling

YIhao Bu, Dan Lian, Zhenguo Gao

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Few-step diffusion sampling sharpens the tension between ODE and SDE dynamics. ODE samplers are stable but can lose diversity, while the standard SDE endpoint can become unreliable at low numbers of function evaluations (NFE). The challenge is therefore not simply whether stochasticity should be added, but which driver properties allow stochastic correction to contribute diffusion without losing finite-step control. We show that this tradeoff is governed by two driver-level quantities, the asymptotic covariance $Q$, which sets the effective diffusion level on the ODE-to-SDE spectrum, and the Poisson solution norm $C_\chi$, which controls the finite-step remainder. Gaussian drivers have $C_\chi = \infty$, so this finite-step remainder is not uniformly controlled by the same bound. Balancing the diffusion level set by $Q$ with the finite-step control set by $C_\chi$ formalizes a favorable regime for bounded structured drivers with intermediate diffusion strength. This regime directly gives a structured correction method, instantiated as Fast-Driver Sampler (FDS) with the shuffled-Lorenz driver. Across DiT-XL/2 and EDM2, FDS establishes a stronger low-NFE frontier among evaluated training-free samplers, improving ODE baselines while avoiding the degradation of the SDE endpoint.

Poster
A Dynamic Decomposition Strategy for the MOEA/D With Proven Performance Guarantees

Benjamin Doerr, Martin S. Krejca, Noé Weeks

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The MOEA/D is one of the most successful multi-objective evolutionary algorithms. It operates by decomposing the optimization problem into single-objective subproblems, which are then solved in a co-evolutionary manner. The performance of the MOEA/D depends critically on this decomposition. In this work, we propose a novel way to adjust this decomposition on the fly, for the case of discrete bi-objective optimization. Different from all previous works in this direction, we support our new algorithm with a proven performance guarantee. This is the first work that rigorously proves the runtime of a dynamic multi-objective evolutionary algorithm. For monotonic distortions of the simple LOTZ benchmark, it is known that classic decompositions leave large holes in the Pareto front, making it very hard for the MOEA/D to cover the entire Pareto front. In contrast, we prove that our self-adjusting MOEA/D solves all these LOTZ problems in an expected number of $O(n^4)$ function evaluations. This relatively low runtime as well as the details of our mathematical proof show that the dynamic decomposition strategy indeed evolves a decomposition adjusted to each of these problem instances.

Poster
A Diagnostic Benchmark for Layered Layout and Template-Variant Reasoning

Jaejung Seol, Haonan Zhu, Elad Hirsch, Adrienne Deganutti, Purvanshi Mehta

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Graphic-design layouts are structured, multi-layered artifacts: a single composition specifies the position, type, z-order, and styling of dozens of components, and a single template typically begets a family of sibling variants that share its structural theme but differ in content, palette, or imagery -- properties that flat-canvas layout benchmarks discard. We introduce \textsc{GraphicDesignBench} (GDB), a diagnostic benchmark of $16$ tasks along two axes: \emph{spatial composition} ($8$ understanding + $4$ generation) and \emph{template variants} ($3$ understanding + $2$ generation), grounded in a new dataset of $1{,}148$ real-world templates with full component hierarchy, per-element styling, and sibling groupings. Across four frontier VLMs (GPT-5.4, Gemini-3.1-Pro / Flash-Lite, Claude-Opus-4.6) and two image generators (GPT-Image-1.5, Gemini-3.1-Flash-Image), GDB exposes concrete and dissociated gaps: component detection sits an order of magnitude below natural-image baselines, layer-order reasoning decouples from other spatial skills, partial completion collapses from single- to multi-element settings, and a simple font-Jaccard baseline matches or exceeds frontier VLMs on sibling matching and clustering. We release the dataset, tasks, metrics, and per-model outputs to track where current models are, and are not, ready to act as design collaborators.

Poster
A Deep Learning Framework for Scalar-on-Function Models

Ruiqi Liu, Suneel Babu Chatla

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We propose a deep learning framework for scalar-on-function regression with possibly multiple functional predictors observed on irregular grids. The method represents each functional covariate by finitely many basis coefficients computed from the observed trajectories and fits a deep neural network using these coefficients as features. We establish a general nonasymptotic excess risk bound for the neural network estimator that decomposes the error into statistical, truncation, discretization, and network approximation terms. We then specialize the theory to two important settings. (i) For continuous functional models, an equal-width neural network estimator achieves a nearly minimax optimal rate up to a log-logarithm factor. (ii) For functional multiple-index models, we design a bottleneck-equal-width neural network estimator that exploits the low-dimensional index-link structure and attains a nearly minimax optimal rate up to a logarithm factor. The results provide theoretical support for neural network-based scalar-on-function regression and highlight the importance of architecture design.

Poster
A Composite Activation Function for Learning Stable Binary Representations

Seokhun Park, Choeun Kim, Kwanho Lee, Sehyun Park, Insung Kong, Yongdai Kim

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Activation functions play a central role in neural networks by shaping internal representations. Recently, learning binary activation representations has attracted significant attention due to their advantages in computational and memory efficiency, as well as interpretability. However, training neural networks with Heaviside activations remains challenging, as their non-differentiability obstructs standard gradient-based optimization. In this paper, we propose Heavy-Tailed Activation Function (HTAF), a smooth approximation to the Heaviside function that enables stable training with gradient-based optimization. We construct HTAF as a sigmoid–hyperbolic tangent composite function and theoretically show that it maintains a large gradient mass around zero inputs while exhibiting slower gradient decay in the tail regions. We show that Spiking Neural Networks, Binary Neural Networks and Deep Heaviside neural Networks can be trained stably using HTAF with gradient-based optimization. Finally, we introduce Implicit Concept Bottleneck Models (ICBM), an interpretable image model that leverages HTAF to induce discrete feature representations. Extensive experiments across various architectures and image datasets demonstrate that ICBM enables stable discretization while achieving prediction performance comparable to or better than standard models.

Poster
A Closer Look at Dynamic Scene Graph Generation in the Era of Multimodal Large Language Models

Xuanming Cui, Jaiminkumar Ashokbhai Bhoi, Chionh W Peng, Adriel Kuek, Ser Nam Lim

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Dynamic Scene Graph Generation (DSGG) aims to capture objects and their evolving relations in videos. Despite recent progress, the practicality and quality of generated scene graphs remain limited compared to the rapid advances in Multimodal Large Language Models (MLLMs). In this work, we revisit DSGG from two fundamental perspectives: task setup and model design. From the task setup perspective, we identify two key limitations of the current recall-oriented evaluation protocol: (i) a severe precision–recall trade-off, and (ii) uninformative and redundant relation generation. To better assess practical usefulness, we introduce four additional metrics that provide a more comprehensive evaluation of the quality of generated dynamic scene graphs. From the model design perspective, we explore directly using MLLMs for scene graph generation and establish a strong MLLM-based DSGG baseline through three design changes. First, we replace the conventional bottom-up pipeline with a top-down reason-then-locate strategy. Second, we reformulate frame-wise dynamic graphs as Temporal Relation Set (TRS) prediction, improving both efficiency and performance. Third, we introduce Importance-Aware Finetuning (IAF) to encourage more relevant and diverse relation generation. Extensive experiments on Action Genome, VidVRD, and PVSG show that our approach consistently achieves state-of-the-art performance across multiple metrics.

Poster
A Bitter Lesson for Data Filtering

Christopher Mohri, John Duchi, Tatsunori Hashimoto

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We investigate data filtering for large model pretraining via new scaling studies that target the high compute, data-scarce regime. In spite of an apparently common belief that filtering data to include only high-quality information is essential, our experiments suggest that with enough compute, the best data filter is no data filter. We find that sufficiently trained large parameter models not only tolerate low-quality and distractor data, but in fact, including nominally 'poor' data improves model performance.

Spotlight
A Benchmark for Omni-Modal Reasoning in Long Videos

Mohammed Irfan Kurpath, Jaseel M Kaithakkodan, Jinxing Zhou, Sahal Shaji Mullappilly, Mohammad Almansoori, Noor Ahsan, Beknur Kalmakhanbet, Sambal Shikhar, Rishabh Lalla, Jean Lahoud, Mariette Awad, Fahad Shahbaz Khan, Salman Khan, Rao Anwer, Hisham Cholakkal

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Long-form omni-modal video understanding requires models to integrate vision, speech, and ambient audio with coherent long-context reasoning. Existing video benchmarks often trade off temporal scale, modality coverage, open-ended interaction, and interpretable scoring. To address this gap, we introduce $\textbf{LongShOTBench}$, a long video evaluation benchmark designed around three coupled goals: holistic omni-modal integration, intent-driven open-ended interaction, and rubric-level diagnosis. It constructs single- and multi-turn questions from practical viewing scenarios, involving systematical tasks for probing visual, speech, ambient-audio, temporal, and cross-modal reasoning. Each item includes a reference answer and a weighted criterion-level rubric, enabling evaluation to identify which perceptual facts, temporal links, modality-grounding requirements, and reasoning steps are satisfied or missed. All samples are manually verified and corrected to improve grounding, clarity, and rubric reliability. We also introduce $\textbf{LongShOTAgent}$, a training-free omni-modal evidence-seeking agent that couples full-video preprocessing with targeted retrieval, query-adaptive segment refinement, and explicit claim verification over visual, speech, and non-speech audio evidence. Its iterative search-refine-verify loop exposes intermediate evidence and lets modality-specific specialists re-analyze relevant moments before answering. We perform comprehensive evaluation of 105 video-capable models spanning open-source omni-modal models, vision-language systems, audio LLMs, agentic pipelines and closed-source APIs. Across this broad evaluation, current MLLMs remain far from saturating LongShOTBench, while our LongShOTAgent emerges as the strongest training-free system, reaching 66.64\% overall. By releasing the benchmark, leaderboard, and agentic method, our work provides the community with a shared, interpretable testbed for evaluating and advancing long-form omni-modal video reasoning.

Poster
3DSPA: A 3D Semantic Point Autoencoder for Evaluating Video Realism

Bhavik Chandna, Kelsey Allen

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AI video generation is evolving rapidly. For video generators to be useful for applications ranging from robotics to film-making, they must consistently produce realistic videos. However, evaluating the realism of generated videos remains a largely manual process -- requiring human annotation or bespoke evaluation datasets which have restricted scope. Here we develop an automated evaluation framework for video realism which captures both semantics and coherent 3D structure and which does not require access to a reference video. Our method, 3DSPA, is a **3D** **S**emantic **P**oint **A**utoencoder utoencoder which is trained to reconstruct held out 3D point trajectories which have been augmented with DINO semantic features. By combining both semantic and geometric representations, 3DSPA enables robust assessments of realism, temporal consistency, and physical plausibility in generated videos. Experiments show that 3DSPA outperforms leading VLMs by more than 10\% in identifying videos which violate physical laws, and more than doubles the correlations between human and auto-eval ratings in judging physical common sense and motion quality across multiple generative video datasets. Our results demonstrate that enriching trajectory-based representations with 3D semantics offers a strong foundation for benchmarking generative video models, and implicitly captures physical rule violations.

Poster
3DCodeBench: Benchmarking Agentic Procedural 3D Modeling Via Code

Yipeng Gao, Lei Shu, Genzhi Ye, Xi Xiong, Ameesh Makadia, Meiqi Guo, Laurent Itti, Jindong Chen

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Procedural 3D modeling through code is emerging as a versatile paradigm, offering deterministic, engine-ready, and precisely editable assets that neural 3D generators inherently lack. Authoring such procedural content, however, demands deep expertise in 3D software APIs, parametric design, and code-level geometric reasoning. In this paper, we propose 3DCodeBench, a systematic benchmark for evaluating vision-language model (VLM) agents for procedural 3D generation in 3D modeling software. Specifically, 3DCodeBench evaluates how effectively 11 advanced VLMs can serve as procedural 3D modelers by transferring text and image references into procedural code for software. Recognizing that automated metrics may not fully capture the perceptual quality of 3D shapes, we build 3DCodeArena, a ranking platform based on human preference between generated pairs. From extensive evaluations and results, we observe that: (1) Failures mostly arise from API usage, while successful renders still suffer from disconnected or floating 3D geometric components. (2) Test-time scaling, such as higher thinking budgets and multi-turn refinement, improves performance overall. Our findings highlight a critical need for high-quality procedural coding data to advance commercial VLMs. Furthermore, effective procedural 3D modeling requires a robust execution environment that provides high-fidelity feedback for iterative refinement. To accelerate research in this domain, we release 3DCodeBench—including the curated data, benchmark, evaluation protocol, and qualitative results—as a foundational tool for developing VLM-based 3D modelers.

Poster
3D-PLOT-LLM: Part-Level Object Tokens for 3D Large Language Models

Jintang Xue, Xinyu Wang, Yixing Wu, Jingwen Chen, C.-C. J Kuo

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3D multimodal large language models (3D MLLMs) describe a 3D object as a whole but cannot address, name, or reason about its parts. Prior part-aware attempts add segmentation decoders, heavier 3D encoders, or bounding-box grammars at substantial parameter cost. We take a fundamentally different path: we reorganize the input token stream so that parts become directly addressable through the LLM’s own vocabulary. Our model, 3D-PLOT-LLM, partitions the frozen point encoder’s patches into K locally coherent regions and inserts, before each region’s patch tokens, a learnable per-region marker and a reserved vocabulary token \; a Marker-Space Refinement (MSR) module then conditions each marker on its region’s spatial statistics and adjacency neighbors. The model thus cites parts in its output and follows prompts that refer to parts by token, a capability absent from prior object-level 3D MLLMs. To probe this interface, we construct PartVerse-QA, a vocabulary-level part-QA benchmark adapted from PartVerse mesh annotations (77K training pairs and 588 held-out queries on disjoint object splits), on which 3D-PLOT-LLM reaches caption-to-slots Jaccard 0.459 and Exact-match 13.78% (+64% relative over the strongest non-MSR variant), with a slot-to-caption GPT-4o judge of 44.68. On the 3DCoMPaT-GrIn part-aware grounded description benchmark, 3D-PLOT-LLM outperforms PointLLM, Kestrel, PARIS3D, and SegPoint on every text-output metric, and ShapeLLM on 3 of 4, with up to +3.03 GPT-4o judge over PointLLM. On Objaverse whole-object captioning, adding PartVerse-QA at Stage 2 yields +0.65 SBERT and +1.85 GPT-4o over PointLLM, and tops PointLLM-PiSA on 4 of 5 traditional metrics (SBERT, SimCSE, BLEU-1, METEOR) despite targeting a different (part-grounded) objective. All with under 1M new trainable parameters on a frozen point encoder, an order of magnitude below prior part-aware 3D MLLMs, and no segmentation decoder or bounding-box head.

Poster