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Tensor-Based Synchronization and the Low-Rankness of the Block Trifocal Tensor
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Shows the block trifocal tensor of calibrated/uncalibrated cameras has an explicit Tucker factorization with multilinear rank (6,4,4) independent of camera count, and uses HOSVD with hard thresholding (HOSVD-HT) to jointly recover scales and camera poses for synchronization.
Problem
Recovering global camera poses (locations and orientations) from the block trifocal tensor of three-view geometry, where each trifocal tensor block is known only up to an unknown scale and many blocks are missing.
Approach
The block trifocal tensor factors as a Tucker product with a fixed 6x4x4 core and camera-dependent factor matrices, giving a low multilinear rank (6,4,4) regardless of the number of cameras; this rank constraint fixes the unknown block scales and enables a tensor-completion-style HOSVD synchronization.
Key results
- Block trifocal tensor has multilinear rank (6,4,4) independent of number of cameras when cameras are not collinear and scales are fixed.
- Proposed method achieves the best location estimation on 4 of 6 EPFL datasets and competitive translation errors on 8 of 14 Photo Tourism datasets.
- Rotation estimation is superior on only 2 of 6 EPFL datasets, and it reaches reasonable rotation estimates on 10 of 14 Photo Tourism datasets, below LUD.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use trifocal-tensor synchronization instead of two-view synchronization | camera location estimation on EPFL datasets · EPFL | location estimation: 4 out of 6 datasets | Mixed |
| use trifocal-tensor synchronization instead of two-view synchronization | camera location estimation · Photo Tourism datasets with estimation percentage above 60% | location estimation: 6 out of 8 datasets | Helped |
| use trifocal-tensor synchronization instead of two-view synchronization | camera location estimation · Photo Tourism datasets with estimation percentage below 60% | location estimation: 2 out of 6 datasets | Mixed |
| use trifocal-tensor synchronization instead of two-view synchronization | camera rotation estimation · EPFL | rotation estimation: 2 out of 6 datasets | Mixed |
| use trifocal-tensor synchronization instead of two-view synchronization | camera rotation estimation · Photo Tourism | rotation estimation: 10 out of 14 datasets | Mixed |
Surprising findings
- The method fails on CastleP19 and CastleP30 because sparse triplet graphs prevent high completion rates.
- The algorithm works well only when the signs of the unknown scales are mostly uniform; the synthetic experiment manually corrected signs using ground truth.
Limitations
- Rotation estimates are weaker than location estimates and below LUD on many datasets.
- Performance depends on the density of trifocal tensor estimates; sparse viewing graphs (e.g., CastleP19/30) fail.
- Cubic scaling in number of cameras limits scalability to large datasets.
Experimental setup
Datasets: EPFL datasets Photo Tourism datasets
Benchmarks: EPFL Photo Tourism
Metrics: mean translation error median translation error rotation error
Baselines: NRFM LUD BATA MPLS
Builds on: HARD-IMPUTE Tyler's M-estimator GlueStick STE NRFM LUD BATA
Closest papers by meaning
- QuadSync: Quadrifocal Tensor Synchronization via Tucker Decomposition (CVPR 2026 · similarity 0.92)
- Pose Synchronization Under Multiple Pair-Wise Relative Poses (CVPR 2023 · similarity 0.88)
- Cycle-Sync: Robust Global Camera Pose Estimation through Enhanced Cycle-Consistent Synchronization (NeurIPS 2025 · similarity 0.86)
- Improving Robustness for Joint Optimization of Camera Pose and Decomposed Low-Rank Tensorial Radiance Fields (AAAI 2024 · similarity 0.85)
- Performance Gaps in Multi-view Clustering under the Nested Matrix-Tensor Model (ICLR 2024 · similarity 0.83)
- Efficient Detection of Long Consistent Cycles and its Application to Distributed Synchronization (CVPR 2024 · similarity 0.83)
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