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Sparse-view Pose Estimation and Reconstruction via Analysis by Generative Synthesis
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Proposes SparseAGS, which jointly refines camera poses and 3D (via DreamGaussian-style multi-view SDS with a 6-DoF Zero-1-to-3 prior) from off-the-shelf pose estimates, with iterative outlier removal and discrete-plus-continuous pose correction.
Problem
Joint camera pose estimation and 3D reconstruction from sparse unposed object-centric views, where initial pose estimates may contain large errors and sparse observations under-constrain 3D.
Approach
Extends analysis-by-synthesis with a finetuned 6-DoF novel-view diffusion prior (Zero-1-to-3 with 18-dim 6-DoF camera conditioning) used via multi-view SDS, plus iterative outlier detection (removing images that degrade reconstruction of others) and a discrete sphere-sampling pose search with LPIPS/MSE ranking to correct outlier poses.
Key results
- With DUSt3R initialization on NAVI at N=8, the method reaches 83.7% Rot.@5° (vs 52.3% for DUSt3R alone) and 93.5% CC@0.1 (vs 82.2%).
- On NAVI with 8 views and Ray Diffusion initialization, PSNR improves from 13.44 (no outlier handling) to 15.30 and F1@0.01 from 57.2 to 68.2 after outlier removal and correction.
- For 3D reconstruction on NAVI with N=10, the method reaches 18.03 PSNR / 0.1660 LPIPS with DUSt3R init, versus LEAP 12.98 / 0.2890.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| refine initial pose estimates with SparseAGS | RelPose++ · NAVI, 8 images | Rot.@5°: 10.9 -> 42.1 | Helped |
| refine initial pose estimates with SparseAGS | Ray Diff. · NAVI, 8 images | CC@0.1: 38.3 -> 80.4 | Helped |
| refine initial pose estimates with SparseAGS | DUSt3R · NAVI, 8 images | Rot.@5°: 52.3 -> 83.7 | Helped |
| refine initial DUSt3R poses with SPARF | DUSt3R · NAVI, 8 images | Rot.@15°: 93.8 -> 87.8 | Hurt |
| refine initial poses with SparseAGS rather than pose-free reconstruction | LEAP · NAVI, 8 images | PSNR: 12.93 -> 17.03 | Helped |
| add generative SDS priors to pose-3D co-optimization (ablation) | Pose-3D co-optimization without SDS · NAVI, 8 images, Ray Diff. initialization | PSNR: 12.72 -> 13.44 | Helped |
| use vanilla Zero123 camera conditioning instead of no SDS (ablation) | Pose-3D co-optimization · NAVI, 8 images, Ray Diff. initialization | Rot.@15°: 79.9 -> 78.3 | Hurt |
| use 6-DoF rather than vanilla Zero123 camera conditioning (ablation) | SDS pose-3D co-optimization · NAVI, 8 images, Ray Diff. initialization | Rot.@5°: 30.2 -> 34.6 | Helped |
| add outlier removal and correction (ablation) | SDS with 6-DoF Zero123 · NAVI, 8 images, Ray Diff. initialization | Rot.@5°: 34.6 -> 60.3 | Helped |
| add outlier removal and correction (ablation) | SDS with 6-DoF Zero123 · NAVI, 8 images, Ray Diff. initialization | PSNR: 13.44 -> 15.30 | Helped |
| add outlier removal and correction (ablation) | SDS with 6-DoF Zero123 · NAVI, 8 images, Ray Diff. initialization | F1@0.01: 57.2 -> 68.2 | Helped |
Surprising findings
- SPARF's correspondence-based pose refinement degraded accuracy relative to some initializations (e.g., Rot.@15° dropped for RelPose++ and DUSt3R), attributed to false correspondences.
- Vanilla Zero-1-to-3 as a generative prior reduced camera rotation and center accuracy at 15° and CC@0.1 compared to no prior, due to its 3-DoF camera parameterization.
Limitations
- Requires reasonable off-the-shelf pose estimates; fails if a large fraction of initial predictions have large error.
- Does not handle truncation or occlusion, so close-up partial views or cluttered scenes are unsupported.
- Evaluated only in an object-centric setting.
Experimental setup
Datasets: NAVI CO3D Objaverse GSO ABO OmniObject3D
Benchmarks: NAVI GSO ABO OmniObject3D
Metrics: Rotation accuracy@5° Rotation accuracy@15° Camera center accuracy@0.1 PSNR LPIPS F1@0.01
Baselines: RelPose++ Ray Diffusion DUSt3R SPARF LEAP UpFusion ID-Pose
Builds on: DreamGaussian Zero-1-to-3 SPARF Score Distillation Sampling
Closest papers by meaning
- LEAP: Liberate Sparse-View 3D Modeling from Camera Poses (ICLR 2024 · similarity 0.92)
- No Pose, No Problem: Surprisingly Simple 3D Gaussian Splats from Sparse Unposed Images (ICLR 2025 · similarity 0.91)
- Cameras as Rays: Pose Estimation via Ray Diffusion (ICLR 2024 · similarity 0.90)
- Sparse3D: Distilling Multiview-Consistent Diffusion for Object Reconstruction from Sparse Views (AAAI 2024 · similarity 0.89)
- SPARS3R: Semantic Prior Alignment and Regularization for Sparse 3D Reconstruction (CVPR 2025 · similarity 0.89)
- SPAR3D: Stable Point-Aware Reconstruction of 3D Objects from Single Images (CVPR 2025 · similarity 0.89)
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