Splat2Real: Novel-view Scaling for Physical AI with 3D Gaussian Splatting
Authors: Hansol Lim, Jongseong Brad Choi
Organizations: Department of Mechanical Engineering, State University of New York, Korea, 21985, Republic of Korea. · Department of Mechanical Engineering, State University of New York, Stony Brook, Stony Brook, NY 11794, USA.
Physical AI faces viewpoint shift between training and deployment, and novel-view robustness is essential for monocular RGB-to-3D perception. We cast Real2Render2Real monocular depth pretraining as imitation-learning-style supervision from a digital twin oracle: a student depth network imitates expert metric depth/visibility rendered from a scene mesh, while 3DGS supplies scalable novel-view observations. We present Splat2Real, centered on novel-view scaling: performance depends more on which views are added than on raw view count. We introduce CN-Coverage, a coverage+novelty curriculum that greedily selects views by geometry gain and an extrapolation penalty, plus a quality-aware guardrail fallback for low-reliability teachers. Across 20 TUM RGB-D sequences with step-matched budgets (N=0 to 2000 additional rendered views, with N unique <= 500 and resampling for larger budgets), naive scaling is unstable; CN-Coverage mitigates worst-case regressions relative to Robot/Coverage policies, and GOL-Gated CN-Coverage provides the strongest medium-high-budget stability with the lowest high-novelty tail error. Downstream control-proxy results versus N provides embodied-relevance evidence by shifting safety/progress trade-offs under viewpoint shift.
Figures & tables
Fig. 1: Splat2Real pipeline. Real captures build a 3DGS observation teacher for high-throughput novel-view RGB rendering; simulator-style mesh rendering provides aligned metric oracle labels. A scaling policy (Random/Robot/Coverage/CN-Coverage) selects viewpoint budget N . Gated/composited fallback is used as a secondary safety layer.
Metric
Value
Split/frames
Median abs depth error (m)
0.028 ± 0.019
held-out real frames
Mean abs depth error (m)
0.088 ± 0.111
held-out real frames
Valid-pixel fraction
0.875 ± 0.171
held-out real frames
TABLE I: Mesh-oracle fidelity.
Fig. 2: Step-matched scaling: metric AbsRel vs budget N for Random, Robot, Coverage, CN-Coverage, CN-Coverage (MeshHist), and GOL-Gated CN-Coverage. Error bars denote 95% CI across sequences; connecting lines are guides to the eye. Budgets are discrete and plotted on categorical x-axis positions. The dashed vertical marker at N=500 denotes the unique-view cap; for N>500 , training samples with replacement from the selected set (resampling-based count scaling).
N
Random
Robot
Coverage
CN-Coverage
CN-Coverage (MeshHist)
GOL-Gated CN-Coverage
0
0.36 ± 0.05
0.35 ± 0.06
0.34 ± 0.04
0.35 ± 0.05
0.30 ± 0.07
0.31 ± 0.07
25
0.36 ± 0.07
0.35 ± 0.08
0.36 ± 0.07
0.35 ± 0.08
0.31 ± 0.05
0.28 ± 0.05
50
0.36 ± 0.09
0.37 ± 0.09
0.37 ± 0.10
0.38 ± 0.07
0.33 ± 0.08
0.40 ± 0.12
100
0.35 ± 0.06
0.37 ± 0.09
0.36 ± 0.08
0.40 ± 0.10
0.34 ± 0.07
0.36 ± 0.09
200
0.38 ± 0.07
0.39 ± 0.10
0.39 ± 0.06
0.40 ± 0.12
0.38 ± 0.11
0.31 ± 0.04
500
0.36 ± 0.08
0.44 ± 0.12
0.40 ± 0.11
0.36 ± 0.09
0.33 ± 0.09
0.31 ± 0.06
TABLE II: Novel-view scaling.
Method
Mean
Worst
Range
GOL-Gated CN-Coverage
0.317
0.328
0.020
CN-Coverage (MeshHist)
0.356
0.390
0.066
Random
0.367
0.382
0.028
CN-Coverage
0.374
0.399
0.044
Coverage
0.397
0.416
0.035
Robot
0.446
0.482
0.096
TABLE III: Scaling stability summary.
Method
N
400-step
2000-step
Δ
GOL-Gated CN-Coverage
200
0.322 ± 0.087
0.253 ± 0.046
-0.069
Random
200
0.369 ± 0.092
0.314 ± 0.046
-0.055
GOL-Gated CN-Coverage
2000
0.356 ± 0.082
0.263 ± 0.051
-0.093
Random
2000
0.362 ± 0.092
0.316 ± 0.042
-0.046
TABLE IV: Convergence-budget control.
Fig. 3: AbsRel versus surface-coverage fraction. Each point is one (sampler, N ) setting.
Mode
Scenes
Tail@0
Tail@2000
Δ Tail
CN-Coverage
20
0.367 ± 0.063
0.387 ± 0.116
0.020 ± 0.082
CN-Coverage (MeshHist)
20
0.330 ± 0.088
0.408 ± 0.136
0.079 ± 0.062
Coverage
20
0.350 ± 0.053
0.419 ± 0.132
0.069 ± 0.109
GOL-Gated CN-Coverage
20
0.319 ± 0.072
0.348 ± 0.115
0.030 ± 0.083
Random
20
0.377 ± 0.060
0.387 ± 0.117
0.010 ± 0.082
Robot
20
0.385 ± 0.091
0.462 ± 0.154
0.077 ± 0.098
TABLE V: Tail summary.
Fig. 4: Error versus pose-novelty bins at low/high N in vertical subpanels: (a) N=0 , (b) N=2000 . The x-axis uses per-sequence novelty quantile bins 1–5 (1 = least novel, 5 = most novel), so all 20 sequences contribute to each panel. Shaded regions denote 95% CI across sequences.
Fig. 5: Teacher-quality interaction scatter at multiple budgets, where Δ AbsRel = AbsRel(GS) − AbsRel(mesh+Hist) and negative is better. Dashed line marks gate threshold qs=1.0 . Correlations (Pearson/Spearman) are N=0 : 0.06/ −0.07 , N=500 : 0.21/0.08, N=2000 : −0.23 / −0.11 .
Setting
Value
Total scenes
20
High-quality scenes (q_s ¿= 1)
10
Low-quality scenes (q_s ¡ 1)
10
High-quality rate
0.500
PSNR threshold
10.000
SSIM threshold
0.200
TABLE VI: Gating protocol.
Fig. 6: Success-collision Pareto across budgets N (each point annotated by N ).
Mode
N
Succ
Col/100
Col/fail
Path
CN-Coverage
0
0.226 ± 0.026
0.900 ± 0.341
0.140 ± 0.053
0.281 ± 0.026
CN-Coverage
200
0.523 ± 0.031
22.892 ± 2.225
5.759 ± 0.417
0.647 ± 0.029
CN-Coverage
500
0.514 ± 0.031
21.525 ± 2.104
5.315 ± 0.394
0.625 ± 0.029
CN-Coverage
1000
0.386 ± 0.030
11.667 ± 1.734
2.280 ± 0.320
0.429 ± 0.029
Coverage
0
0.226 ± 0.026
0.900 ± 0.341
0.140 ± 0.053
0.281 ± 0.026
Coverage
200
0.280 ± 0.028
4.458 ± 1.037
0.743 ± 0.171
0.291 ± 0.027
TABLE VII: Downstream control proxy.
Condition
AbsRel
RMSE
SIlog
Scale
d1
real (upper)
0.221 ± 0.086
0.505 ± 0.171
21.556
0.163
0.605 ± 0.160
mesh
0.283 ± 0.104
0.583 ± 0.213
24.000
0.226
0.506 ± 0.160
mesh+DR
0.308 ± 0.098
0.621 ± 0.213
25.575
0.255
0.458 ± 0.180
mesh+Hist
0.281 ± 0.149
0.527 ± 0.150
22.192
0.221
0.560 ± 0.187
mesh+AdaIN
0.279 ± 0.115
0.563 ± 0.155
24.724
0.220
0.523 ± 0.145
3DGS
0.315 ± 0.073
0.726 ± 0.239
27.978
0.257
0.379 ± 0.168
TABLE A.1: Sim2Real results.
N
Comp
Scenes
MedD
MeanD
p
200
Best non-guardrail
20
0.030
-0.076
0.869
200
Coverage
20
-0.047
-0.081
0.00558
200
Random
20
-0.042
-0.074
0.00944
2000
Best non-guardrail
20
-0.003
-0.032
0.498
2000
Coverage
20
-0.023
-0.058
0.0121
2000
Random
20
-0.020
-0.031
0.0826
TABLE A.2: Paired Wilcoxon tests.
Mode
NPoints
Pearson
Spearman
All
48
0.182
0.182
Random
8
0.296
0.244
Robot
8
0.909
0.952
Coverage
8
0.899
0.903
CN-Coverage
8
0.452
0.390
CN-Coverage (MeshHist)
8
0.658
0.537
TABLE A.3: Coverage correlation.
N
BestSampler
BestAbsRel
Coverage
0
CN-Coverage (MeshHist)
0.298 ± 0.066
0.771
25
GOL-Gated CN-Coverage
0.283 ± 0.045
0.823
50
CN-Coverage (MeshHist)
0.331 ± 0.084
0.860
100
CN-Coverage (MeshHist)
0.342 ± 0.066
0.905
200
GOL-Gated CN-Coverage
0.308 ± 0.036
0.946
500
GOL-Gated CN-Coverage
0.309 ± 0.058
0.971
TABLE A.4: Scaling summary.
Method
AbsRel
RMSE
d1
mesh+Hist
0.302
0.759
0.354
3DGS
0.452
1.107
0.152
GOL-Gated
0.363
0.882
0.263
TABLE A.5: Holdout check.
N
Bucket
Qual.
Scenes
Mean ± std
Median
Frac( Δ<0 )
0
High-q
qs≥1
10
0.034 ± 0.071
0.034
0.10
0
Low-q
qs<1
10
0.069 ± 0.166
0.087
0.20
500
High-q
qs≥1
10
0.069 ± 0.091
0.044
0.10
500
Low-q
qs<1
10
0.007 ± 0.105
0.019
0.50
2000
High-q
qs≥1
10
-0.096 ± 0.147
-0.021
0.60
2000
Low-q
qs<1
10
0.025 ± 0.107
0.020
0.40
TABLE A.6: Teacher-quality buckets.
Domain
Frames
LPIPS
PSNR
SSIM
3DGS
720
0.677 ± 0.075
10.855 ± 2.690
0.373 ± 0.151
mesh(vertex)
720
0.522 ± 0.105
11.374 ± 3.393
0.442 ± 0.153
mesh+Hist
720
0.499 ± 0.088
13.524 ± 3.166
0.506 ± 0.187
mesh-shaded(sim)
720
0.767 ± 0.053
5.863 ± 1.342
0.341 ± 0.161
TABLE A.7: Domain gap.
Component
Value
Units
GPU
NVIDIA GeForce RTX 5090
–
Teacher build time (n=19)
2.529 ± 0.392
s/sequence
3DGS setup
non-iterative init; voxel =0.020 m, points =45000 , iters =0
–
GS render throughput
219.89
views/s
Student training time (reference, 6 epochs)
36.22
s
Student inference speed (320x240)
552.56
FPS
TABLE A.8: Runtime.
Scenes
MedianErr (m)
MeanErr (m)
ValidFrac
20
0.028 ± 0.019
0.088 ± 0.111
0.875 ± 0.171
TABLE A.9: Mesh fidelity.
Name
Sampler
Observation source
Mixing rule
Random / Robot / Coverage
corresponding pose policy
3DGS RGB observations
none
CN-Coverage
coverage + bounded-novelty greedy policy
3DGS RGB observations
none
CN-Coverage (MeshHist)
CN-Coverage
mesh RGB with per-scene LAB Reinhard transfer to train real-RGB statistics
none
mesh+AdaIN
Coverage (reference schedule only)
mesh RGB with AdaIN style transfer using a sampled train-split real frame as style reference
none
GOL-Gated CN-Coverage
CN-Coverage
3DGS or mesh+Hist RGB
Bernoulli scene-level mixing with probability g(qs)
Prevailing 2D-centric visuomotor policies exhibit a pronounced deficiency in novel view generalization, as their reliance on static observations hinders consistent action mapping across unseen views. In response, we introduce GenSplat, a feed-forward 3D Gaussian Splatting framework that facilitates view-generalized policy learning through novel view rendering. GenSplat employs a permutation-equivariant architecture to reconstruct high-fidelity 3D scenes from sparse, uncalibrated inputs in a single forward pass. To ensure structural integrity, we design a 3D-prior distillation strategy that regularizes the 3DGS optimization, preventing the geometric collapse typical of purely photometric supervision. By rendering diverse synthetic views from these stable 3D representations, we systematically augment the observational manifold during training. This augmentation forces the policy to ground its decisions in underlying 3D structures, thereby ensuring robust execution under severe spatial perturbations where baselines severely degrade.
3D Gaussian Splatting (3DGS) renders novel views in real time, but an uncertainty heatmap does not certify that a rendered view meets a certain prediction coverage. We treat novel-view synthesis as structured regression and ask that, with probability at least 1−α, RGB prediction boxes cover at least a 1−β fraction of pixels in a new view. We propose View-Structured Conformal Prediction (VSCP). It splits the pre-calibration scale into a spatial shape from the renderer and a transferable view-difficulty factor, which predicts the smallest view-wise multiplier that shape needs. A held-out quantile over views (View-CP) then gives finite-sample validity even when transferring to new scenes. The same factorization makes the analysis exact: a conformity score is the ratio of oracle to predicted view difficulty, and excess width separates into a test-side and a calibration-side term. Across 13 real scenes, pixel-pooled calibration reaches 89.9% marginal pixel coverage but only 61.4% view-event coverage at a 90% target, while View-CP reaches 91.7--92.0%. At matched coverage VSCP cuts width by 22.1% against a constant scale, and matches a ten-model ensemble's 21.0% reduction using only one model per scene and four rather than ten rasterization passes per query. VSCP also improves on the closest single-model baseline, the 3DGS-U field, by 4.7 points (p=0.0225). The view predictor transfers from bounded source families to all nine unbounded Mip-NeRF360 scenes. There the full scale beats the constant scale with 20.7% width saving on all nine scenes. It also keeps an 18.3% saving under a different densification backbone and runs at 216--280 FPS on an RTX4090.
Junzheng Chu, Bin Pan, Zhenwei Shi
School of Statistics and Data Science, LEBPS, KLMDASR, LPMC, AAIS, NITFID, Nankai University · Department of Aerospace Intelligent Science and Technology, School of Astronautics, Beihang University
We introduce ReconSplat, a feed-forward model for 3D scene reconstruction that aims to address the longstanding trade-off between plausible view generation for unobserved regions and geometric consistency, providing both geometrically aligned novel views and sharp depth estimates. Our approach builds on 3D Gaussian splatting (3DGS) as an intermediate differentiable scene representation and integrates it with a multi-view latent diffusion model (MV-LDM) trained to act simultaneously as a refiner and an inpainter for appearance and scene geometry. We enforce geometric consistency by guiding the diffusion process with variational 3D latent features for appearance and geometry, encoded by the feed-forward 3DGS representation and rasterized to 2D latent space. ReconSplat produces both photorealistic novel views and accurate depth maps on real-world benchmarks, RealEstate10K and DL3DV-10K, outperforming existing methods in challenging extrapolation setups. Notably, ReconSplat allows the extrapolation of unseen and challenging viewpoints jointly with coherent and precise scene geometry.
Giuseppe Stracquadanio, Kevin Raj, Julia Grabinski +1