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EquiPose: Exploiting Permutation Equivariance for Relative Camera Pose Estimation
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Proposes EquiPose, a framework that makes any end-to-end relative pose network permutation-equivariant (P21 = P12^-1) by symmetrizing its two-order predictions via a geodesic rotation mean, improving baselines with or without fine-tuning.
Problem
End-to-end relative camera pose networks do not satisfy pose permutation equivariance: estimating pose from I1 to I2 and from I2 to I1 yields inconsistent results (the reverse should be the inverse).
Approach
Define a pose permutation equivariant (PPE) mapping and construct it from any baseline by averaging the two orderings: rotation is the geodesic mean of R12 and R21^T, translation is (t12 - R*12 t21)/2; a theorem proves the output is PPE, and only one extra forward pass of the decoder is needed by reusing shared encoder features.
Key results
- On ScanNet, GRelPose+EquiPose† reduces rotation error from 8.16 to 7.61 and translation error from 0.38 to 0.28 m.
- Inference-only EquiPose improves all five baselines on ScanNet across the eight metrics (e.g., GRelPose RE 8.16 to 7.97).
- EquiPose enforces dR and dt of zero exactly, while random permutation training leaves nonzero differences (e.g., GRelPose dR 3.2 to 0 vs 2.1 with RP).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| apply EquiPose at inference | GRelPose · ScanNet test | RE: 8.16 -> 7.97 | Helped |
| fine-tune under EquiPose | GRelPose + EquiPose · ScanNet test | TE: 0.32 -> 0.28 | Helped |
| apply EquiPose at inference | GRelPose · 7-Scene | Rot. AUC @5°: 45.47 -> 46.85 | Helped |
| fine-tune under EquiPose | GRelPose + EquiPose · 12-Scene | Rot. AUC @5°: 56.67 -> 58.11 | Helped |
| apply EquiPose at inference | GRelPose · Mapfree | Pr.: 12.7 -> 13.0 | Helped |
| apply EquiPose at inference | MFQuat · Mapfree | VCRE median error: 160.7 -> 166.4 | Hurt |
| train with random permutation | EightVit · ScanNet test | RE: 8.90 -> 8.23 | Helped |
| add EquiPose to random-permutation training (ablation) | EightVit + RP · ScanNet test | RE: 8.23 -> 8.20 | Helped |
| train with random permutation | MF6D · ScanNet test | RE: 9.81 -> 8.17 | Helped |
| add EquiPose to random-permutation training (ablation) | MF6D + RP · ScanNet test | RE: 8.17 -> 7.74 | Helped |
| train with random permutation | GRelPose · ScanNet test | RE: 8.16 -> 7.74 | Helped |
| add EquiPose to random-permutation training (ablation) | GRelPose + RP · ScanNet test | RE: 7.74 -> 7.65 | Helped |
Surprising findings
- Random permutation training improves average errors but cannot strictly enforce the PPE property, and EquiPose trained under random permutation still gains further.
Limitations
- Extra computation depends on baseline decoder/aggregation cost; heavy decoders incur high overhead.
- Requires two decoder passes at inference, doubling cost in the worst case.
- Evaluated only on indoor and outdoor pose datasets with specific baselines.
Experimental setup
Datasets: ScanNet 7-Scenes 12-Scenes Mapfree
Benchmarks: ScanNet 7-Scenes 12-Scenes Mapfree
Metrics: rotation AUC @3/5/10 deg translation AUC @0.1/0.2/0.5 m rotation error translation error pose error VCRE dR dt params FLOPs
Baselines: ExtremeRotation Reg6D EightVit MF6D GRelPose MFBin MFBinTS MFQuat MFQuatTS
Builds on: ExtremeRotation GRelPose MF6D EightVit Reg6D
Closest papers by meaning
- From Correspondences to Pose: Non-minimal Certifiably Optimal Relative Pose without Disambiguation (CVPR 2024 · similarity 0.87)
- 3D-Aware Hypothesis & Verification for Generalizable Relative Object Pose Estimation (ICLR 2024 · similarity 0.85)
- Relative Pose Estimation through Affine Corrections of Monocular Depth Priors (CVPR 2025 · similarity 0.85)
- UNOPose: Unseen Object Pose Estimation with an Unposed RGB-D Reference Image (CVPR 2025 · similarity 0.85)
- FAR: Flexible Accurate and Robust 6DoF Relative Camera Pose Estimation (CVPR 2024 · similarity 0.85)
- CARL: A Framework for Equivariant Image Registration (CVPR 2025 · similarity 0.85)
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