Generating 3D assets with explicit parts requires two properties at once: geometric detail inside each part and structural coherence across the whole object. Recent image-conditioned 3D generation models adopt a structured 3D representation that anchors tokens to explicit spatial positions, capturing both properties, but their output remains a single fused mesh. We ask how a part-decomposed generation model can inherit both properties of these holistic priors, and answer with STRUCTPARTS, a framework whose core technical contribution is a dual-frame coordinate interleaving mechanism: each shape latent is interpreted under both a part-local and an object-global reference frame, and processed through a global-local inter-leaved transformer that simultaneously reuses the prior's geometric detail at the part scale and its structural coherence at the whole-object scale. As its structural input, STRUCTPARTS uses a segmented mesh scaffold, a coarse mesh paired with a face-level segmentation mask kept entirely within the prior's native 3D representation. With only lightweight finetuning, both intra-part detail and inter-part coherence emerge from the same pretrained weights. On PartObjaverse-Tiny, STRUCTPARTS matches or surpasses prior part-decomposed models at a fraction of their training cost, while naturally supporting part-mesh refinement and part-level editing.
Figures & tables
Figure 1: Diverse decomposed 3D objects generated by our approach using images from recent open-source image generation models Z-Image Team, Alibaba Group (2025) ; Black Forest Labs (2025) . Among them, the guns, train, crab, and motorcycle are specifically displayed in exploded views
Figure 2: Overview of StructParts ’s pipeline. Given a single image, our method first constructs a 3D segmented scaffold using the structure generation model followed by a segmentation model. We then sample points from each part surface to construct the voxel indices in both the per-part normalized space and the shared global-shape space. These voxel indices serve as position embeddings to guide the diffusion model’s sampling process. The segmented scaffold and part meshes depicted here are dataset-provided ground truth (GT), used to illustrate the part-wise data flow.
Figure 3: Layout-conditioned part decomposition. Comparison among methods that accept an explicit layout (HoloPart, X-Part, FullPart, OmniPart): each row shows assembled shapes for part coherency and exploded views for per-part geometry. Baselines drop fine details, leave incomplete shapes, or introduce floaters; StructParts preserves both by reusing the holistic prior.
Table 4
Figure 4: Image-to-decomposed-parts comparison. Top two rows: in-the-wild prompts generated by flux-2 Black Forest Labs (2025) ; bottom row: an in-distribution test sample. For each input we show the assembled shape and a zoom-in view. PartPacker / PartCrafter struggle to produce semantically meaningful decompositions; FullPart and OmniPart suffer from boundary collisions;
Method
Part-level
Shape-level
CD ↓
F-0.05 ↑
F-0.10 ↑
CD ↓
F-0.05 ↑
F-0.10 ↑
StructParts
0.107
0.67
0.77
0.008
0.93
0.97
GRoPE + part embed.
0.125
0.63
0.74
0.012
0.83
0.91
GRoPE only
0.143
0.63
0.75
0.019
0.70
0.90
LRoPE only
0.331
0.20
0.36
0.054
0.51
0.73
Table 3: Ablation Study of dual-frame positional embedding strategies. Quantitative results evaluated at both part-level and shape-level.
Figure 5: Ablation on positional-embedding strategies. Three variants compared against StructParts ’ dual frame: LRoPE only loses global structure (parts treated identically in their own normalized frames); GRoPE only recovers global layout but degrades small or off-center parts under unnormalized coordinates; GRoPE + part embed. (as in prior work) still misses fine geometric detail. Only the dual-frame design recovers both global structure and per-part detail.
Figure 8
Figure 8: Limitations: inaccurate scaffolds. Each example shows the input image, scaffold with segmentation, and exploded generation. Although our method generates geometric detail, inaccuracies in the input scaffold can persist in the generated parts.
Appendix figures & tables8 assets
Supplementary material from the paper’s appendix.
Appendix
Quantity
StructParts
X-Part (matched)
GPUs
8 H200
8 H200
Total allocation
768 GPU-hours
768 GPU-hours
Trainable parameters
3.051 B
3.315 B
TFLOPs/object
92.7
137.4
Allocated GPU memory
82.71 GB
115 GB
Appendix
Table 4: Training allocation and computational cost. Both methods use 512 tokens per part and the same GPU-hour allocation. TFLOPs/object include forward and backward computation under the same PyTorch profiler. Optimizer steps and processed-part counts are reported with checkpoint quality in Tab. 5 .
Table 5: Checkpoint quality and training-schedule accounting. Part-level evaluation on PartObjaverse-Tiny. The 40K StructParts and 28K X-Part runs use the same GPU-hour allocation; the 20K StructParts checkpoint is included to compare quality after fewer optimizer steps and processed parts.
Table 6: Geometry preservation and scaffold perturbations. The input scaffold and generated outputs are evaluated against the same GT shapes with identical normalization and surface sampling. Noise is normal-direction vertex displacement as a percentage of the bounding-box diagonal; label corruption reassigns boundary voxels. All other inference settings are fixed.
Table 7: Part-level sensitivity to segmentation errors. We corrupt GT boundary labels to retain a known correspondence between each generated and GT part. These results are distinct from the assembled-shape experiment in Tab. 6 .
Table 8: Cross-dataset evaluation on ABO. A fixed 200-object subset is evaluated with identical inputs and the same whole-shape CD/F-score protocol for all methods. Released and matched-budget X-Part checkpoints are distinguished.
Category
FullPart
HoloPart
OmniPart
X-Part
StructParts
Animals
0.395/0.317
0.120/0.031
0.182/0.205
0.040 /0.013
0.095/ 0.009
Buildings & Outdoor
0.483/0.389
0.166/0.068
0.403/0.386
0.100/0.027
0.068/0.013
Daily-used
0.259/0.122
0.199/0.043
0.229/0.191
0.119/0.024
0.066/0.011
Electronics
0.453/0.256
0.150/0.061
0.165/0.146
0.152/0.029
0.137/0.022
Human-shaped
0.332/0.273
0.081/0.028
0.177/0.148
0.049/0.011
0.041/0.009
Transportation
0.377/0.238
0.181/0.065
0.332/0.211
0.208/0.044
0.144/0.022
Appendix
Table 9: Category-wise part-level CD on PartObjaverse-Tiny. Each cell reports mean / median CD, using the six largest evaluation categories. X-Part denotes its released checkpoint.
Category
Objects
Paired parts
StructParts
X-Part
Human-Shape
29
423
0.74/0.83
0.74/0.85
Animals
23
344
0.74 /0.82
0.72/0.84
Daily-Use
25
335
0.71/0.81
0.62/0.74
Buildings & Outdoor
25
370
0.67/0.79
0.61/0.72
Transportation
38
615
0.59/0.70
0.52/0.64
Electronics
34
523
0.63/0.74
0.58/0.71
Appendix
Table 10: Category counts and paired-part F-scores. Object counts describe the evaluation set; paired parts have complete matched predictions. F-score pairs are [email protected] / [email protected]. X-Part denotes its released checkpoint.
Table 11: Paired bootstrap differences against released X-Part. Objects with complete paired predictions are resampled 10,000 times, retaining all paired parts within each sampled object. Differences are StructParts minus X-Part. F-score estimates and interval bounds use two decimals; a negative bound that rounds to zero retains its sign. Statistical conclusions use the unrounded intervals.
Part-level 3D assets are essential for editing, reassembly, and interaction, yet recovering such structure from a single image remains challenging due to occlusion, ambiguous boundaries, and the need for coherent multi-part reasoning. Existing approaches struggle to achieve both controllable part-level generation and coherent multi-part structure, as part identity and spatial allocation are typically inferred implicitly. We present Seg3DParts, a segmentation-grounded framework for controllable part-level 3D generation from a single image. By treating segmentation as an explicit grounding signal, our method defines part identity during generation, enabling each component to be anchored to a corresponding image region. To ensure coherent assemblies, we introduce structured cross-part interaction that allows components to exchange global context throughout the generative process. As a result, Seg3DParts directly generates well-aligned part meshes in a shared canonical space without post-hoc alignment, supporting flexible and controllable decomposition. We further introduce PartObjectNet, a large-scale dataset with over 200K objects and 1M annotated parts. Experiments demonstrate that Seg3DParts achieves superior geometry quality, cross-part coherence, and part-level controllability over existing methods.
Jiantao Lin, Meixi Chen, Yingjie Xu +5
The Hong Kong University of Science and Technology (Guangzhou) · Knowin AI · The Hong Kong University of Science and Technology
Interactive 3D assets used in games and simulation are typically decomposed into specific semantic parts to support animation, physics, and scripted behaviors, yet most generative 3D models produce either monolithic meshes or arbitrary part decompositions that cannot be aligned with application-specific requirements. We present CubePart, a generative framework for open-vocabulary, part-controllable 3D mesh generation that exposes part structure as an explicit inference-time control signal. Given a global text prompt and a user-defined parts schema expressed as an open-ended list of part names, our method generates a set of meshes - one per schema element - that assemble into a coherent object while respecting the specified semantic structure. To enable this capability, we introduce a scalable data pipeline to construct a large open-vocabulary, part-labeled 3D dataset, along with a two-stage generative architecture that separates global shape synthesis from part-level decoding. We demonstrate that the resulting assets can be directly integrated into game engines and driven by animation and behavior scripts without manual post-processing. Project Page: https://cubepart.github.io/
Part-aware 3D generation aims to create digital assets that are coherent as complete objects while exposing structural parts for editing, material assignment, animation, and reuse. Existing methods impose this structure outside the native generation loop: segmentation-based methods partition an already generated shape, while additive methods synthesize parts from predefined layouts, boxes, or tokens and then reconcile them into a whole. The former preserves the generated geometry but fixes the object before part boundaries are determined; the latter exposes part cardinality but often leaves shared boundaries vulnerable to gaps, interpenetrations, and material discontinuities. In this paper, we propose SCULPT, a framework that addresses these challenges through subtractive composition. Given a complete object represented in a structured 3D latent space, SCULPT iteratively applies a joint split predictor to generate one extracted part together with the remaining object. The predictor performs a coupled denoising process conditioned on both the image and the current 3D state, so the extracted part and updated remainder are generated together rather than reconciled after generation. The joint split predictor processes both outputs on the union of their native sparse 3D supports, allowing neighboring supports to overlap rather than imposing a disjoint voxel partition. The rollout ends when the remainder support becomes empty or reaches a fixed safety cap, allowing the number of generated parts to adapt to each object within that bound. Extensive experiments demonstrate state-of-the-art geometry on PartObjaverse while preserving strong complete-object reconstruction after part assembly. Results on four dataset images, one text-to-image-generated input, and one real-world photograph further show fine-grained textured part decomposition beyond the benchmark.
Sikuang Li, Chen Yang, Jiemin Fang +5
Shanghai Jiao Tong University · This work was done during an internship at Huawei. · Huawei