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D^3CTTA: Domain-Dependent Decorrelation for Continual Test-Time Adaption of 3D LiDAR Segmentation
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Proposes D3CTTA, a backpropagation-free online continual test-time adaptation method for LiDAR segmentation that combines distance-aware prototypes with KNN pseudo-label filtering and domain-specific feature decorrelation.
Problem
Continual test-time adaptation of pre-trained LiDAR segmentation models to shifting domains (sensor, weather, corruption) without source data, avoiding costly backpropagation and large batch sizes.
Approach
Builds prototypes per distance-based density region, filters pseudo-labels with KNN spatial consistency, and applies RanPAC-style closed-form feature decorrelation with separate Gram matrices per domain, where domains are detected via BN-statistic similarity and Wasserstein distance.
Key results
- On Synth4D to SemanticKITTI-C, average mIoU of 30.82 vs 24.25 for source and 29.15 for EATA (best prior), a 5.7% gain over previous SOTA, without backpropagation.
- On Synth4D to nuScenes-C, average mIoU of 24.15 vs 20.75 for source and 23.76 for EATA.
- Decorrelation alone raises mean mIoU from 24.25 to 30.17 in the SemanticKITTI-C ablation.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use D3CTTA instead of EATA | MinkowskiNet · Synth4D to SemanticKITTI-C, average | mIoU: 29.15 -> 30.82 | Helped |
| use D3CTTA instead of EATA | MinkowskiNet · Synth4D to nuScenes-C, average | mIoU: 23.76 -> 24.15 | Helped |
| add decorrelation (ablation) | D3CTTA on Synth4D to SemanticKITTI-C · SemanticKITTI-C | average mIoU: 24.25 -> 30.17 | Helped |
| add domain detection to decorrelation (ablation) | D3CTTA on Synth4D to SemanticKITTI-C · SemanticKITTI-C | average mIoU: 30.17 -> 30.32 | Helped |
| add prototype learning to decorrelation and domain detection (ablation) | D3CTTA on Synth4D to SemanticKITTI-C · SemanticKITTI-C | average mIoU: 30.32 -> 30.17 | Hurt |
| add distance-aware prototypes (ablation) | D3CTTA on Synth4D to SemanticKITTI-C · SemanticKITTI-C | average mIoU: 30.17 -> 30.44 | Helped |
| add KNN filtering to the full modules (ablation) | D3CTTA on Synth4D to SemanticKITTI-C · SemanticKITTI-C | average mIoU: 30.44 -> 30.82 | Helped |
| select pseudo-labels with entropy top 30% instead of no filtering (ablation) | D3CTTA · Synth4D to SemanticKITTI-C | mIoU: 30.44 -> 29.38 | Hurt |
| select pseudo-labels with entropy top 50% instead of no filtering (ablation) | D3CTTA · Synth4D to SemanticKITTI-C | mIoU: 30.44 -> 29.85 | Hurt |
| select pseudo-labels with entropy top 70% instead of no filtering (ablation) | D3CTTA · Synth4D to SemanticKITTI-C | mIoU: 30.44 -> 30.36 | Hurt |
| select pseudo-labels with probability top 30% instead of no filtering (ablation) | D3CTTA · Synth4D to SemanticKITTI-C | mIoU: 30.44 -> 29.34 | Hurt |
| use KNN spatial-consistency filtering instead of no filtering (ablation) | D3CTTA · Synth4D to SemanticKITTI-C | mIoU: 30.44 -> 30.82 | Helped |
Surprising findings
- Stricter entropy or probability pseudo-label selection lowered mIoU despite higher pseudo-label accuracy, attributed to biased prediction distributions under large domain gaps.
- Pseudo-label accuracy did not directly correlate with final performance; selecting only ground-truth-correct labels did not improve results in one experiment.
Limitations
- Degrades in certain domains (e.g., beam missing, cross sensor on nuScenes-C) and underperforms some baselines there.
- Relies only on a simple distance prior rather than richer geometric features.
- Pseudo-label bias remains an open problem; more refined filtering is needed.
Experimental setup
Datasets: Synth4D SemanticKITTI-C nuScenes-C
Benchmarks: Synth4D to SemanticKITTI-C Synth4D to nuScenes-C repeated domains Synth4D to SemanticKITTI-C
Metrics: mIoU
Baselines: Source TENT GIPSO EATA ViDA T3A PSLabel
Builds on: RanPAC T3A CoTTA GIPSO TENT
Closest papers by meaning
- MOS: Model Synergy for Test-Time Adaptation on LiDAR-Based 3D Object Detection (ICLR 2025 · similarity 0.88)
- An Empirical Study of the Generalization Ability of Lidar 3D Object Detectors to Unseen Domains (CVPR 2024 · similarity 0.87)
- Construct to Associate: Cooperative Context Learning for Domain Adaptive Point Cloud Segmentation (CVPR 2024 · similarity 0.86)
- Multi-Space Alignments Towards Universal LiDAR Segmentation (CVPR 2024 · similarity 0.86)
- TREND: Unsupervised 3D Representation Learning via Temporal Forecasting for LiDAR Perception (NeurIPS 2025 · similarity 0.86)
- Three Pillars Improving Vision Foundation Model Distillation for Lidar (CVPR 2024 · similarity 0.86)
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