REVIEW 4 major objections 4 minor 54 references
"Stack It Up!": 3D Stable Structure Generation from 2D Hand-drawn Sketch
T0 review · 4 major / 4 minor · reviewed 2026-08-06 · deepseek-v4-flash
Pith's one-line read A rough 2D front-view sketch, stripped to its geometric relations and stability patterns, is enough to generate a stable 3D block structure.
desk verdict A plausible and well-motivated sketch-to-3D pipeline, but the supplied full text is unreadable so the stability claim is unverified; worth a real referee if the actual paper is intact. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is the abstract relation graph, a symbolic description of the sketch's geometric relations and stability patterns. It carries the argument because it converts an unstructured drawing into a compact, noise-free specification that diffusion models can condition on, and the iterative hidden-support prediction is what lets the graph include blocks that are not drawn.
What would settle it
Run the system on a set of front-view sketches chosen so that two different stable 3D structures share the same visible relations, such as a cantilevered balcony with and without a hidden rear pillar, then physically simulate or build the outputs: the central claim fails if the method cannot recover a stable arrangement that matches the sketch's visible relations.
Extended reading notes
Core claim
StackItUp claims that the gap between a rough 2D front-view sketch and a precise 3D block arrangement can be closed by first abstracting the sketch into a relation graph. The graph keeps symbolic geometric relations such as left-of and on-top-of, along with named stability patterns such as two-pillar-bridge, and discards noisy metric details. A set of compositional diffusion models then grounds this graph into concrete 3D block poses, and an iterative loop updates the graph by predicting hidden internal and rear supports that are needed for stability but invisible in the sketch. On sketches of landmarks and house designs, the system consistently produces stable, multilevel structures and beats all compared baselines on both stability and visual resemblance.
Load-bearing premise
The load-bearing premise is that the symbolic relations and stability patterns extracted from a noisy 2D front-view sketch carry enough information for the learned models to infer accurate 3D block poses, including supports that are hidden behind or inside the structure.
Editorial extensions
If this is right
- Non-experts can specify a complex 3D stacking goal with one front-view sketch, without computing exact block poses or using CAD.
- The generated structures stay stable even though the sketch hides rear and internal supports, because the pipeline explicitly predicts and adds those supports.
- Because noisy metric details are discarded during abstraction, the input can be a rough hand drawing rather than a precise blueprint.
- The compositional diffusion grounding allows multilevel structures that go beyond single-level or template-based stacking.
Reading between the lines
- An untested implication is that improving the sketch-to-graph parser, rather than scaling the pose diffusion model, should yield the largest stability gains.
- The pipeline could be reused for other block assemblies such as furniture, scaffolding, or masonry if the stability pattern library were extended to those domains; the paper only demonstrates architectural landmarks and house designs.
- A single front view leaves depth underdetermined, so the system must rely on a learned prior over plausible structures; adversarial sketches with unusual cantilevers are the most natural way to expose its limits.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes StackItUp, a system that takes a 2D front-view hand-drawn sketch, abstracts it into a relation graph capturing symbolic geometric relations (e.g., left-of) and stability patterns (e.g., two-pillar-bridge), grounds this graph to 3D block poses using compositional diffusion models, and iteratively updates it by predicting hidden internal and rear supports. The abstract claims that this approach enables non-experts to specify complex 3D structures from sketches and that it consistently produces stable, multilevel 3D structures, outperforming all baselines on both stability and visual resemblance when evaluated on sketches of landmarks and house designs. The supplied full text is almost entirely garbled, so the technical details, experimental protocol, and quantitative results cannot be verified from the available material.
Significance. If the central claims hold, the paper would offer a practical bridge between rough 2D sketches and 3D block arrangements usable by robot manipulation systems, an appealing direction for non-expert human-robot interaction. The idea of using an abstract relation graph to discard noisy sketch metrics while preserving symbolic relations is a plausible and potentially valuable design choice. However, the manuscript as supplied does not provide verifiable evidence: the abstract is the only readable portion, and it contains no quantitative results, experimental protocol, or stability verification mechanism. The paper cannot be assessed for correctness on the basis of the available text, and the load-bearing claims of consistent stability and baseline superiority remain unsubstantiated.
major comments (4)
- [Full text (garbled)] The supplied full text is almost entirely corrupted (appearing as mojibake), so the method description, equations, experimental setup, and results are unreadable. This is a load-bearing issue: the abstract's claims of 'consistently produces stable' and 'outperforms all baselines' cannot be checked against any accessible evidence. A readable and complete manuscript is required before the contribution can be evaluated.
- [Abstract] The abstract states that StackItUp 'consistently produces stable, multilevel 3D structures' but does not describe any stability verification mechanism such as a physics simulation, a static-equilibrium solver, or a constraint check. Because a 2D front-view sketch does not uniquely determine depth, infinitely many rear and internal support arrangements can project to the same sketch; the stability claim therefore needs a concrete post-hoc verification step or a formal guarantee on the learned support prediction. Please specify how stability is measured and verified for each generated structure.
- [Abstract] The abstract refers to 'stability patterns (e.g., two-pillar-bridge)', which suggests a finite pattern library. The space of possible support configurations for arbitrary sketches is effectively unbounded, so the paper must explain how the finite library covers the full range of support configurations or describe the mechanism that generalizes beyond the library. Without such an explanation, the qualifier 'consistently' is not supported even if the described examples succeed.
- [Abstract] The abstract claims that StackItUp 'outperforms all baselines in both stability and visual resemblance' but gives no quantitative metrics, baseline names, or statistical significance information. Since the full text is unreadable, I cannot verify whether the comparisons are fair, whether the baselines are appropriate, or whether the reported improvements are within noise. The experimental section must provide explicit metrics, error bars, and a description of the baselines and evaluation protocol.
minor comments (4)
- [Abstract] The abstract would be clearer if it formally defined the symbolic relation types (e.g., left-of) and stability patterns (e.g., two-pillar-bridge) or referenced a figure where these are illustrated.
- [Abstract] The term 'visual resemblance' is used without a definition; please specify the metric (e.g., IoU, Chamfer distance, or human evaluation) in the final version.
- [Abstract] The motivating example of a child sketching the Eiffel Tower is engaging, but the abstract does not state the scope of supported sketches (e.g., block size, number of blocks, or single-front-view assumption); a brief scope statement would set expectations.
- [Full text (garbled)] Even after restoring the text, please ensure that the paper explicitly states the diffusion model architecture, training data, and the iterative support-prediction update rule, as these are central to the method and currently only tersely described in the abstract.
Circularity Check
No significant circularity identified; the abstract describes an intermediate graph representation and external comparison against baselines, with no visible self-citation chain or fitted-input-as-prediction.
full rationale
The available readable content is limited to the abstract; the full text is corrupted by character-encoding replacement and is not reliably usable for equation-level inspection. Within the abstract, the claimed derivation is: a 2D sketch is abstracted into a relation graph, the graph is grounded to 3D poses using compositional diffusion models, and hidden internal and rear supports are iteratively predicted. The final claim of stability and visual resemblance is supported by comparison against baselines. No step in this chain reduces to its own input by construction: the relation graph is an intermediate representation, not a renamed version of the output; the hidden-support prediction is an additional component, not a re-fitting of the stability metric; and no parameter is described as fitted to a subset and then reported as a prediction. No load-bearing self-citation is visible in the abstract. Concerns about depth ambiguity or the coverage of the stability-pattern library are correctness or generalization risks, not circularity, and there is insufficient text to substantiate any specific reduction. Under the hard rule that circularity requires quoting a specific reduction, no circular step can be identified, and the honest finding is no significant circularity.
Assumptions & free parameters
free parameters (1)
- diffusion model weights =
not specified
assumptions (3)
- domain assumption A 2D front-view sketch, after abstraction to a relation graph, carries enough information to reconstruct a stable 3D block structure.
- domain assumption Stability can be expressed through a small set of symbolic patterns such as two-pillar-bridge.
- domain assumption Hidden internal and rear supports can be predicted from the visible sketch and current graph.
invented entities (2)
-
abstract relation graph
-
named stability patterns (e.g., two-pillar-bridge)
Cite this review
Pith. "Pith review of "Stack It Up!": 3D Stable Structure Generation from 2D Hand-drawn Sketch." pith.science (2026). https://pith.science/paper/GK53MFYJ
@misc{pith2026250802093,
author = {Pith},
title = {Pith review of: "Stack It Up!": 3D Stable Structure Generation from 2D Hand-drawn Sketch},
year = {2026},
howpublished = {\url{https://pith.science/paper/GK53MFYJ}},
note = {Machine review of arXiv:2508.02093}
}
read the original abstract
Imagine a child sketching the Eiffel Tower and asking a robot to bring it to life. Today's robot manipulation systems can't act on such sketches directly-they require precise 3D block poses as goals, which in turn demand structural analysis and expert tools like CAD. We present StackItUp, a system that enables non-experts to specify complex 3D structures using only 2D front-view hand-drawn sketches. StackItUp introduces an abstract relation graph to bridge the gap between rough sketches and accurate 3D block arrangements, capturing the symbolic geometric relations (e.g., left-of) and stability patterns (e.g., two-pillar-bridge) while discarding noisy metric details from sketches. It then grounds this graph to 3D poses using compositional diffusion models and iteratively updates it by predicting hidden internal and rear supports-critical for stability but absent from the sketch. Evaluated on sketches of iconic landmarks and modern house designs, StackItUp consistently produces stable, multilevel 3D structures and outperforms all baselines in both stability and visual resemblance.
Reference graph
Works this paper leans on
-
[1]
write newline
" write newline "" before.all 'output.state := FUNCTION n.dashify 't := "" t empty not t #1 #1 substring "-" = t #1 #2 substring "--" = not "--" * t #2 global.max substring 't := t #1 #1 substring "-" = "-" * t #2 global.max substring 't := while if t #1 #1 substring * t #2 global.max substring 't := if while FUNCTION format.date year duplicate empty "emp...
- [2]
-
[3]
A. Holladay, J. Barry, L. P. Kaelbling, and T. Lozano-Pérez. Object Placement as Inverse Motion Planning . In IEEE Int. Conf. on Robotics & Automation, 2013
work page 2013
-
[4]
F. Suárez-Ruiz and Q.-C. Pham. A Framework for Fine Robotic Assembly . In IEEE Int. Conf. on Robotics & Automation, 2016
work page 2016
- [5]
-
[6]
S. Karaman and E. Frazzoli. Sampling-Based Algorithms for Optimal Motion Planning . Int. J. Robotics Research, 30, 2011
work page 2011
-
[7]
L. E. Kavraki, P. Svestka, J.-C. Latombe, and M. H. Overmars. Probabilistic Roadmaps for Path Planning in High-Dimensional Configuration Spaces . IEEE Trans. on Robotics and Automation, 12, 1996
work page 1996
-
[8]
S. LaValle. Rapidly-Exploring Random Trees: A New Tool for Path Planning . Research Report 9811, 1998
work page 1998
Show all 54 references
-
[9]
N. C . Babi c and D. Rebolj. Culture Change in Construction Industry: From 2D Toward BIM Based Construction . Journal of Information Technology in Construction (ITcon), 21, 2016
2016
-
[10]
C. A. Hunt. The Benefits of Using Building Information Modeling in Structural Engineering . https://digitalcommons.usu.edu/gradreports/319, 2013
2013
-
[11]
Problems of 2D Drawings in Construction Projects , 2023
Novel BIM . Problems of 2D Drawings in Construction Projects , 2023
2023
-
[12]
Traditional Drawings Vs BIM Technology: Why 2D Plans Are No Longer Enough , 2023
Mars BIM . Traditional Drawings Vs BIM Technology: Why 2D Plans Are No Longer Enough , 2023
2023
-
[13]
Are You Harming Your Business by Sticking with 2D? , 2023
Tekla . Are You Harming Your Business by Sticking with 2D? , 2023
2023
-
[14]
Importance of Structural 3D Modeling , 2023
Shalin Designs . Importance of Structural 3D Modeling , 2023
2023
-
[15]
B. Sen, A. Agarwal, G. Singh, B. B., S. Sridhar, and M. Krishna. SCARP: 3D Shape Completion in Arbitrary Poses for Improved Grasping . In IEEE Int. Conf. on Robotics & Automation, 2023
2023
-
[16]
M. Z. Irshad, S. Zakharov, R. Ambrus, T. Kollar, Z. Kira, and A. Gaidon. ShAPO: Implicit Representations for Multi-Object Shape, Appearance, and Pose Optimization . In Proc. European Conference on Computer Vision, 2022
2022
-
[17]
C. R. Garrett, T. Lozano-Perez, and L. P. Kaelbling. FFRob: Leveraging Symbolic Planning for Efficient Task and Motion Planning . Int. J. Robotics Research, 37, 2018 a
2018
-
[18]
C. R. Garrett, T. Lozano-P \'e rez, and L. P. Kaelbling. Sampling-Based Methods for Factored Task and Motion Planning . Int. J. Robotics Research, 37, 2018 b
2018
-
[19]
Z. Yang, J. Mao, Y. Du, J. Wu, J. B. Tenenbaum, T. Lozano-P \'e rez, and L. P. Kaelbling. Compositional Diffusion-Based Continuous Constraint Solvers . In Conference on Robot Learning, 2023
2023
-
[20]
Y. Xu, J. Mao, Y. Du, T. Lozano-Pérez, L. P. Kaelbling, and D. Hsu. Set It Up!: Functional Object Arrangement with Compositional Generative Models . In Proc. Robotics: Science & Systems, 2024
2024
-
[21]
Y. Zhu, J. Tremblay, S. Birchfield, and Y. Zhu. Hierarchical Planning for Long-Horizon Manipulation with Geometric and Symbolic Scene Graphs . In IEEE Int. Conf. on Robotics & Automation, 2021
2021
-
[22]
Y. Du, C. Durkan, R. Strudel, J. B. Tenenbaum, S. Dieleman, R. Fergus, J. Sohl-Dickstein, A. Doucet, and W. Grathwohl. Reduce, Reuse, Recycle: Compositional Generation with Energy-Based Diffusion Models and MCMC . In Proc. Int. Conf. on Machine Learning, 2023
2023
-
[23]
o berg, J. Lindqvist, M. \
A. Sj \"o berg, J. Lindqvist, M. \"O nnheim, M. Jirstrand, and L. Svensson. MCMC-Correction of Score-Based Diffusion Models for Model Composition . arXiv preprint arXiv:2307.14012, 2023
2023
-
[24]
C. M. Barber, R. J. Shucksmith, B. MacDonald, and B. C. W \"u nsche. Sketch-Based Robot Programming . In IEEE Int. Conf. on Image and Vision Computing New Zealand, 2010
2010
-
[25]
Porfirio, L
D. Porfirio, L. Stegner, M. Cakmak, A. Saupp \'e , A. Albarghouthi, and B. Mutlu. Sketching Robot Programs on the Fly . In ACM/IEEE Int. Conf. on Human-Robot Interaction, 2023
2023
-
[26]
Sundaresan, Q
P. Sundaresan, Q. Vuong, J. Gu, P. Xu, T. Xiao, S. Kirmani, T. Yu, M. Stark, A. Jain, K. Hausman, et al. RT-Sketch: Goal-Conditioned Imitation Learning From Hand-Drawn Sketches . In Conference on Robot Learning, 2024
2024
-
[27]
Y. Cui, S. Niekum, A. Gupta, V. Kumar, and A. Rajeswaran. Can Foundation Models Perform Zero-Shot Task Specification for Robot Manipulation? In Learning for Dynamics and Control Conference, 2022
2022
-
[28]
J. Gu, S. Kirmani, P. Wohlhart, Y. Lu, M. G. Arenas, K. Rao, W. Yu, C. Fu, K. Gopalakrishnan, Z. Xu, et al. Robotic Task Generalization Via Hindsight Trajectory Sketches . In First Workshop on Out-of-Distribution Generalization in Robotics at CoRL 2023, 2023
2023
-
[29]
Goldberg, K
A. Goldberg, K. Kondap, T. Qiu, Z. Ma, L. Fu, J. Kerr, H. Huang, K. Chen, K. Fang, and K. Goldberg. Blox-Net: Generative Design-for-Robot-Assembly Using VLM Supervision, Physics Simulation, and a Robot with Reset . arXiv preprint arXiv:2409.17126, 2024
2024 arXiv
-
[30]
Badagabettu, S
A. Badagabettu, S. S. Yarlagadda, and A. B. Farimani. Query2CAD: Generating CAD Models Using Natural Language Queries . arXiv preprint arXiv:2406.00144, 2024
2024 arXiv
-
[31]
Y. Hong, K. Zhang, J. Gu, S. Bi, Y. Zhou, D. Liu, F. Liu, K. Sunkavalli, T. Bui, and H. Tan. LRM: Large Reconstruction Model for Single Image to 3D . In Int. Conf. on Learning Representations, 2024
2024
-
[32]
J. Tang, J. Ren, H. Zhou, Z. Liu, and G. Zeng. DreamGaussian: Generative Gaussian Splatting for Efficient 3D Content Creation . In Int. Conf. on Learning Representations, 2024
2024
-
[33]
L. Sun, T. Yoneda, S. W. Wheeler, T. Jiang, and M. R. Walter. Stackgen: Generating Stable Structures From Silhouettes Via Diffusion . arXiv preprint arXiv:2409.18098, 2024
2024 arXiv
-
[34]
A. Liu, C. Lin, Y. Liu, X. Long, Z. Dou, H.-X. Guo, P. Luo, and W. Wang. Part123: Part-Aware 3D Reconstruction From a Single-View Image . In ACM SIGGRAPH Conference Papers, 2024
2024
-
[35]
R. Liu, R. Wu, B. Van Hoorick, P. Tokmakov, S. Zakharov, and C. Vondrick. Zero-1-to-3: Zero-Shot One Image to 3D Object . In IEEE Int. Conf. on Computer Vision, 2023 a
2023
-
[36]
M. Liu, C. Xu, H. Jin, L. Chen, M. Varma T, Z. Xu, and H. Su. One-2-3-45: Any Single Image to 3D Mesh in 45 Seconds Without Per-Shape Optimization . Advances in Neural Information Processing Systems, 2023 b
2023
-
[37]
M. Liu, R. Shi, L. Chen, Z. Zhang, C. Xu, X. Wei, H. Chen, C. Zeng, J. Gu, and H. Su. One-2-3-45++: Fast Single Image to 3D Objects with Consistent Multi-View Generation and 3D Diffusion . In IEEE Conf. on Computer Vision & Pattern Recognition, 2024
2024
-
[38]
J. Ho, A. Jain, and P. Abbeel. Denoising Diffusion Probabilistic Models . In Advances in Neural Information Processing Systems, 2020
2020
-
[39]
K. Lu, C. Ma, C. Hori, and D. Romeres. KitchenVLA: Iterative Vision‑Language Corrections for Robotic Execution of Human Tasks . In IEEE International Conference on Robotics and Automation Workshop on Safely Leveraging Vision‑Language Foundation Models in Robotics (SafeLVMs@ICR...
2025
-
[40]
Zeng and Y
Y. Zeng and Y. Xu. Learning reward for physical skills using large language model. arXiv preprint arXiv:2310.14092, 2023
2023 arXiv
-
[41]
Sharma, B
P. Sharma, B. Sundaralingam, V. Blukis, C. Paxton, T. Hermans, A. Torralba, J. Andreas, and D. Fox. Correcting robot plans with natural language feedback. arXiv preprint arXiv:2204.05186, 2022
2022 arXiv
-
[42]
A. P. Dani, I. Salehi, G. Rotithor, D. Trombetta, and H. Ravichandar. Human-in-the-loop robot control for human-robot collaboration: Human intention estimation and safe trajectory tracking control for collaborative tasks. IEEE Control Systems Magazine, 40 0 (6): 0 29--56, 2020
2020
-
[43]
Slade, C
P. Slade, C. Atkeson, J. M. Donelan, H. Houdijk, K. A. Ingraham, M. Kim, K. Kong, K. L. Poggensee, R. Riener, M. Steinert, et al. On human-in-the-loop optimization of human--robot interaction. Nature, 633 0 (8031): 0 779--788, 2024
2024
-
[44]
Jiang, Y
C. Jiang, Y. Xu, and D. Hsu. Llms for robotic object disambiguation. arXiv preprint arXiv:2401.03388, 2024
2024 arXiv
-
[45]
Palan, N
M. Palan, N. C. Landolfi, G. Shevchuk, and D. Sadigh. Learning reward functions by integrating human demonstrations and preferences. arXiv preprint arXiv:1906.08928, 2019
1906 arXiv
-
[46]
P. F. Christiano, J. Leike, T. Brown, M. Martic, S. Legg, and D. Amodei. Deep reinforcement learning from human preferences. In Advances in Neural Information Processing Systems, 2017
2017
-
[47]
Xu and D
Y. Xu and D. Hsu. How to tidy up a table: Fusing visual and semantic commonsense reasoning for robotic tasks with vague objectives. arXiv preprint arXiv:2307.11319, 2023
2023 arXiv
-
[48]
B. D. Ziebart, A. Maas, J. A. Bagnell, and A. K. Dey. Maximum entropy inverse reinforcement learning. 2008
2008
-
[49]
Wulfmeier, P
M. Wulfmeier, P. Ondruska, and I. Posner. Maximum entropy deep inverse reinforcement learning. In Advances in Neural Information Processing Systems, 2016
2016
-
[50]
J. Fu, K. Luo, and S. Levine. Learning robust rewards with adversarial inverse reinforcement learning. In Int. Conf. on Learning Representations, 2018
2018
-
[51]
Y. Xu, W. Gao, and D. Hsu. Receding horizon inverse reinforcement learning. In Advances in Neural Information Processing Systems, 2022
2022
-
[52]
Y. Xu, F. Doshi-Velez, and D. Hsu. On the effective horizon of inverse reinforcement learning. In Proceedings of the 24th International Conference on Autonomous Agents and Multiagent Systems, pages 2208--2216, 2025
2025
-
[53]
P. Vincent. A Connection Between Score Matching and Denoising Autoencoders . Neural Comput., 23 0 (7): 0 1661--1674, 2011
2011
-
[54]
Coleman, I
D. Coleman, I. Sucan, S. Chitta, and N. Correll. Reducing the barrier to entry of complex robotic software: a MoveIt! case study. Journal of Software Engineering for Robotics, 2014
2014
Reviewed August 6, 2026 · model on record in the stance chip above.
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