PUP 3D-GS: Principled Uncertainty Pruning for 3D Gaussian Splatting (2406.10219v2)

Abstract: Recent advances in novel view synthesis have enabled real-time rendering speeds with high reconstruction accuracy. 3D Gaussian Splatting (3D-GS), a foundational point-based parametric 3D scene representation, models scenes as large sets of 3D Gaussians. However, complex scenes can consist of millions of Gaussians, resulting in high storage and memory requirements that limit the viability of 3D-GS on devices with limited resources. Current techniques for compressing these pretrained models by pruning Gaussians rely on combining heuristics to determine which Gaussians to remove. At high compression ratios, these pruned scenes suffer from heavy degradation of visual fidelity and loss of foreground details. In this paper, we propose a principled sensitivity pruning score that preserves visual fidelity and foreground details at significantly higher compression ratios than existing approaches. It is computed as a second-order approximation of the reconstruction error on the training views with respect to the spatial parameters of each Gaussian. Additionally, we propose a multi-round prune-refine pipeline that can be applied to any pretrained 3D-GS model without changing its training pipeline. After pruning 90% of Gaussians, a substantially higher percentage than previous methods, our PUP 3D-GS pipeline increases average rendering speed by 3.56$\times$ while retaining more salient foreground information and achieving higher image quality metrics than existing techniques on scenes from the Mip-NeRF 360, Tanks & Temples, and Deep Blending datasets.

• The paper introduces a novel spatial sensitivity pruning score using Fisher information to quantify each Gaussian's impact on reconstruction error.
• It employs a multi-round prune-refine pipeline that iteratively enhances rendering speed and reduces storage without sacrificing quality.
• Benchmark results on datasets like Mip-NeRF 360 and Tanks and Temples show significant improvements in PSNR and rendering performance compared to heuristic methods.

Analysis of PUP 3D-GS: Principled Uncertainty Pruning for 3D Gaussian Splatting

Paper Overview

The paper "PUP 3D-GS: Principled Uncertainty Pruning for 3D Gaussian Splatting" presents a method for efficiently pruning 3D Gaussian splatting (3D-GS) models to optimize storage and rendering resource usage without compromising on image quality metrics. The authors propose a novel, mathematically principled approach to prune Gaussians from 3D scene reconstructions by evaluating the spatial sensitivity of each Gaussian. The sensitivity is based on a second-order approximation of reconstruction error using the Fisher information matrix. This pruning paradigm, which they term PUP 3D-GS, improves both the rendering speed and model storage efficiency while achieving higher fidelity results compared to existing heuristic-based pruning methods.

Technical Contributions

1. Spatial Sensitivity Pruning Score: The authors introduce a sensitivity score based on the spatial parameters of Gaussians (mean positions and scaling factors), effectively capturing uncertainty by approximating the Hessian of the reconstruction error using Fisher information.
2. Multi-Round Prune-Refine Pipeline: The paper proposes a multi-step pipeline where the 3D-GS model undergoes repeated cycles of pruning and fine-tuning. Unlike one-shot pruning methods, the multi-round approach allows the model to recover small residual errors iteratively, resulting in better performance metrics.
3. Patch-wise Sensitivity Computation: To enhance computational efficiency, the sensitivity score computation is performed over image patches rather than at a per-pixel level, which significantly reduces overhead while maintaining high correlation with full per-pixel computations.

Experimental Results

Significant improvements are reported across several benchmarks:

• Mip-NeRF 360 Dataset: After pruning 88.44% of the Gaussians, the PUP 3D-GS method increases rendering speeds by an average of 2.65x while retaining better image quality (PSNR of 26.83) compared to heuristic-based methods like LightGaussian.
• Tanks and Temples Dataset: The method achieves a compelling balance between speed and image quality, notably on challenging scenes, and shows substantial gains in terms of FPS and storage reduction.
• Deep Blending Dataset: PUP 3D-GS similarly outperforms existing pruning methods by retaining more fine details with PSNR and LPIPS metrics superior to LightGaussian's.

Implications

Practical Implications

The PUP 3D-GS method offers significant practical benefits, particularly for devices with limited storage and computational resources. Real-time rendering in applications like augmented reality (AR), virtual reality (VR), and interactive gaming can directly benefit from the efficiency gains. Implementing PUP 3D-GS in production environments could allow these applications to run on less powerful hardware without a compromised user experience, enabling broader accessibility and adoption.

Theoretical Implications

From a theoretical standpoint, the precise second-order sensitivity approximation using Fisher information opens new paths in pruning methodologies. This approach can inspire further research on the application of sensitivity analysis in other areas of machine learning and computer vision. By demonstrating how uncertainty quantification can be used for model compression, this work contributes valuable insights into the role of Fisher information in practical machine learning model optimization.

Future Developments

Looking ahead, several future developments could build on this work:

• Optimized Computational Techniques: Implementing GPU-accelerated and parallel computing techniques to further reduce overhead involved in Fisher information matrix calculations.
• Broader Applicability: Adapting similar uncertainty-based pruning methodologies to other types of neural network models and scene representations beyond 3D-GS, such as neural radiance fields (NeRF).
• Enhanced Pruning Strategies: Exploring dynamic pruning strategies where the number of Gaussians pruned at each step varies adaptively based on a real-time assessment of the residual errors post-pruning.

Conclusion

The PUP 3D-GS framework proposed by the authors effectively introduces a principled method for uncertainty-based pruning that enhances both the rendering speed and model storage efficiency of 3D Gaussian splatting models. By leveraging second-order sensitivity analyses and a multi-round prune-refine workflow, it sets a new benchmark in the domain of model compression and resource optimization in novel view synthesis and 3D scene reconstruction tasks. This work not only demonstrates tangible practical benefits but also contributes to the theoretical understanding of model sensitivity and uncertainty in machine learning contexts.