Research map / Point clouds / Shape and surface completion
Point Cloud Part Editing: Segmentation, Generation, Assembly, and Selection
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Proposes SGAS, a four-stage (segmentation, generation, assembly, selection) point cloud part editing model using per-part GANs on pre-trained part autoencoders with a global discriminator and part masking/selection, plus a new TMDS diversity metric.
Problem
Point cloud part editing needs diverse edited parts, fidelity to unedited parts, and high-quality assembled results; prior methods entangle parts and lack inter-part constraints, requiring manual selection.
Approach
Disentangle parts by independently fitting part-level feature distributions with per-part GANs over pre-trained part autoencoders, conditioned on unedited parts via AdaIN, and enforce assembly constraints with a global discriminator on all part features plus a learned part-selection threshold.
Key results
- Diversity part editing on Chair/Lamp/Table: SGAS average MMD 1.55 vs MSC-cGAN 2.14 and average TMD 5.63 vs 4.84.
- Unsupervised generation on Chair: SGAS COV-EMD 58 vs best baseline 32 (EditVAE M=7), with EMD-MMD 0.076 best among compared models.
- Ablation on number of parts: n=6 gives best MMD-EMD (0.039) and COV-EMD (58) on Airplane.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use SGAS instead of MSC-cGAN | Point cloud part editing · PartNet.v0.Merged Chair | MMD: 1.62 -> 1.33 | Helped |
| Use SGAS instead of MSC-cGAN | Point cloud part editing · PartNet.v0.Merged Average | TMD: 4.84 -> 5.63 | Mixed |
| Set α:β to higher diversity weighting (1:1 to 10:1) (ablation) | SGAS part editing · PartNet.v0.Merged | TMD: 4.36 -> 7.68 | Helped |
| Set α:β to higher diversity weighting (1:1 to 10:1) (ablation) | SGAS part editing · PartNet.v0.Merged | MMD: 1.33 -> 1.40 | Hurt |
| Use 6 parts rather than 2 (ablation) | SGAS generation · ShapeNet-Partseg Airplane | COV EMD: 47 -> 58 | Helped |
| Use 6 parts rather than 13 (ablation) | SGAS generation · ShapeNet-Partseg Airplane | COV EMD: 53 -> 58 | Helped |
| Vary the number of parts from 2 to 13 (ablation) | SGAS generation · ShapeNet-Partseg Airplane | JSD: 0.042; 0.039; 0.040; 0.036; 0.040; 0.035 | Mixed |
Surprising findings
- Part selection is training-free: parts whose latent features fall near zero are simply not decoded, letting the model omit parts such as chair arms.
Limitations
- Without part offset networks, relies on fixed spatial positions of parts, so works only for objects with consistent prototypes (e.g., cannot mix ceiling and table lamps).
- Performance limited by pre-trained part autoencoders; embeddings work better when parts are normalized.
- Unsupervised generation can show gaps between parts, requiring point-count expansion heuristic.
Experimental setup
Datasets: PartNet PartNet.v0.Merged ShapeNet-Partseg ScanNet
Benchmarks: PartNet.v0.Merged ShapeNet-Partseg ScanNet
Metrics: MMD TMD TMDS JSD COV UHD
Baselines: MSC-cGAN TreeGAN MRGAN EditVAE SP-GAN
Builds on: l-GAN Wasserstein GAN with gradient penalty AdaIN EditVAE
Closest papers by meaning
- SeaLion: Semantic Part-Aware Latent Point Diffusion Models for 3D Generation (CVPR 2025 · similarity 0.85)
- FreePoint: Unsupervised Point Cloud Instance Segmentation (CVPR 2024 · similarity 0.85)
- Point-based Instance Completion with Scene Constraints (ICLR 2025 · similarity 0.84)
- Generative 3D Part Assembly via Part-Whole-Hierarchy Message Passing (CVPR 2024 · similarity 0.84)
- Rethinking Point Cloud Data Augmentation: Topologically Consistent Deformation (ICML 2025 · similarity 0.84)
- Improved MLP Point Cloud Processing with High-Dimensional Positional Encoding (AAAI 2024 · similarity 0.84)
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