Active Neural 3D Reconstruction with Colorized Surface Voxel-based View Selection (2405.02568v2)

Abstract: Active view selection in 3D scene reconstruction has been widely studied since training on informative views is critical for reconstruction. Recently, Neural Radiance Fields (NeRF) variants have shown promising results in active 3D reconstruction using uncertainty-guided view selection. They utilize uncertainties estimated with neural networks that encode scene geometry and appearance. However, the choice of uncertainty integration methods, either voxel-based or neural rendering, has conventionally depended on the types of scene uncertainty being estimated, whether geometric or appearance-related. In this paper, we introduce Colorized Surface Voxel (CSV)-based view selection, a new next-best view (NBV) selection method exploiting surface voxel-based measurement of uncertainty in scene appearance. CSV encapsulates the uncertainty of estimated scene appearance (e.g., color uncertainty) and estimated geometric information (e.g., surface). Using the geometry information, we interpret the uncertainty of scene appearance 3D-wise during the aggregation of the per-voxel uncertainty. Consequently, the uncertainty from occluded and complex regions is recognized under challenging scenarios with limited input data. Our method outperforms previous works on popular datasets, DTU and Blender, and our new dataset with imbalanced viewpoints, showing that the CSV-based view selection significantly improves performance by up to 30%.

• The paper introduces ActiveNeuS, which integrates both image rendering and geometric uncertainties to select the most informative training views.
• It employs an efficient grid-based computation to capture neural implicit surface uncertainty, significantly boosting both image rendering and mesh reconstruction quality.
• The method reduces early training bias and computational overhead, paving the way for robust applications in robotic vision and advanced 3D scene modeling.

ActiveNeuS: Enhancing 3D Reconstruction with Neural Implicit Surface Uncertainty

Introduction to Active Learning in 3D Scene Reconstruction

Active learning in the context of 3D scene reconstruction involves selectively choosing the most informative views to train models effectively. Traditionally, methods like Neural Radiance Fields (NeRF) and its variants have used either image rendering or geometric uncertainty independently to guide this view selection. The limitation, however, lies in the fact that relying solely on one type of uncertainty often lacks information about the other, potentially leading to biased early-stage training when input data is sparse.

The Advent of ActiveNeuS

The newly proposed approach, named ActiveNeuS, seeks to remedy the drawbacks of traditional methods by considering both image rendering and geometric uncertainties simultaneously in selecting training views. This dual consideration helps reduce bias inherent in early training phases, providing a more balanced and informative training process.

How ActiveNeuS Works

1. Dual Uncertainty Evaluation: ActiveNeuS computes what’s known as neural implicit surface uncertainty. This not only captures color uncertainty (related to image rendering) but also incorporates surface information (geometric aspect), offering a more holistic view of scene uncertainty.
2. Efficient Uncertainty Integration: By leveraging surface information within a grid structure, ActiveNeuS can quickly and effectively choose diverse viewpoints for training. This method avoids biases that usually occur due to the unequal integration of uncertainties from different scene aspects.
3. Improved Selection Strategy: Using a combination of surface information and uncertainty grids, ActiveNeuS selects views that both cover diverse perspectives and focus on parts of the scene needing more detailed reconstruction, optimizing both learning efficiency and model performance.

Numerical Results and Observations

• Performance Metrics: Studies on popular datasets such as Blender and DTU show that ActiveNeuS outperforms previous methods not only in theoretical metrics but also in practical application, exhibiting significant improvements in image rendering and mesh reconstruction tasks.
• Viewpoint Diversity: The views selected by ActiveNeuS lead to notable improvements in model learning and performance, underscoring the importance of integrating multiple types of uncertainty in training view selection.

Theoretical and Practical Implications

From a theoretical standpoint, the introduction of a dual uncertainty approach by ActiveNeuS sets a new framework for how uncertainties can be handled more comprehensively in 3D reconstruction tasks. Practically, this method promises to reduce the time and computational resources needed to achieve high-fidelity models, as less data is wasted on uninformative views.

Looking Forward: Speculations on Future Developments

There is significant potential for ActiveNeuS to be adapted and expanded in future research. One possible direction could see this method blended with robotic vision systems where active 3D reconstruction is critical. Moreover, extending this approach to handle uncertainties from different types of neural network architectures presents another intriguing area for future exploration.

Lastly, dealing with how uncertainties from different sources and modalities are integrated, especially in complex scenes with various objects and textures, would also pave the way for more robust and versatile 3D reconstruction technologies.