See Eye to Eye: A Lidar-Agnostic 3D Detection Framework for Unsupervised Multi-Target Domain Adaptation (2111.09450v2)

Abstract: Sampling discrepancies between different manufacturers and models of lidar sensors result in inconsistent representations of objects. This leads to performance degradation when 3D detectors trained for one lidar are tested on other types of lidars. Remarkable progress in lidar manufacturing has brought about advances in mechanical, solid-state, and recently, adjustable scan pattern lidars. For the latter, existing works often require fine-tuning the model each time scan patterns are adjusted, which is infeasible. We explicitly deal with the sampling discrepancy by proposing a novel unsupervised multi-target domain adaptation framework, SEE, for transferring the performance of state-of-the-art 3D detectors across both fixed and flexible scan pattern lidars without requiring fine-tuning of models by end-users. Our approach interpolates the underlying geometry and normalizes the scan pattern of objects from different lidars before passing them to the detection network. We demonstrate the effectiveness of SEE on public datasets, achieving state-of-the-art results, and additionally provide quantitative results on a novel high-resolution lidar to prove the industry applications of our framework.

Lidar-Agnostic 3D Detection Framework

The paper "See Eye to Eye: A Lidar-Agnostic 3D Detection Framework for Unsupervised Multi-Target Domain Adaptation" presents a novel approach addressing the critical issue of domain discrepancies in 3D lidar-based object detection systems. This issue arises mainly due to the variation in scan patterns and point sampling methodologies among different lidar sensors. The paper proposes an unsupervised multi-target domain adaptation framework named SEE, which aims to circumvent the need for fine-tuning across multiple lidar configurations, thus providing a robust solution that is sensor-agnostic.

Problem Context and Motivation

The lidar technology spectrum encapsulates a range of sensors with distinct sampling methodologies, resulting in inconsistent object representations across different lidar types. This inconsistency significantly impairs the performance of 3D detectors trained on one type of lidar when deployed on another. With the emergence of adjustable scan pattern lidars, traditional fine-tuning of models becomes impractical due to computational cost and time constraints. This research is motivated by the need to develop a framework that ensures the transferability of state-of-the-art detectors across diverse lidar sensors without additional training by the end-user.

Proposed Framework (SEE)

The core contribution of the paper is the SEE (Sensor-agnostic and Efficient Endeavor) framework, which mitigates the domain gap challenge in 3D object detection through three key phases: object isolation, surface completion (SC), and point sampling.

1. Object Isolation:
   • The process involves separating object points from the point cloud, leveraging instance segmentation. This isolation is crucial, particularly in target domains sans labels.
2. Surface Completion:
   • The framework employs the Ball-Pivoting Algorithm (BPA) to interpolate a triangle mesh for the object, reconstructing its geometry. This step handles partial occlusions and unifies discrete components of objects, enhancing robustness against diverse lidar point distributions.
3. Point Sampling:
   • SEE uses Poisson disk sampling to adjust the point density, emulating high-density data akin to proximate object points, thereby enhancing object clarity for detectors.

Experimental Validation and Results

The SEE framework was evaluated using two state-of-the-art detectors, SECOND-IoU and PV-RCNN, across several public datasets including KITTI, Waymo, and nuScenes, as well as a novel high-resolution Baraja Spectrum-Scan™ dataset. SEE outperformed baseline source-only models consistently, achieving significant improvements in cross-lidar evaluations. Notably, it improved the average precision (AP) scores significantly, illustrated by the leap from 11.92 to 65.52 in 3D AP for SECOND-IoU in the Waymo to KITTI scenario. These improvements underscore SEE's efficacy in maintaining detector performance across different domains without manual dataset annotations.

Implications and Future Developments

The SEE framework potentially transforms the landscape of 3D object detection, particularly in applications demanding cross-sensor operability, such as autonomous driving, surveillance, and robotic perception. By eliminating the need for costly and time-intensive retraining procedures for each new lidar configuration, SEE offers a scalable and practical solution for industrial deployments.

Future research directions could explore integrating deep learning-based shape completion methods to enhance the SC phase, potentially increasing the fidelity of 3D reconstructions. Additionally, expanding SEE to handle a broader class range beyond vehicles could further extend its applicability. There is also potential for SEE to inform developments in end-to-end adaptive learning systems within the unsupervised domain adaptation paradigm, paving the way for universal 3D perception modules.

In conclusion, the SEE framework represents a significant advancement in lidar-agnostic 3D detection, demonstrating substantial promise in streamlining and unifying lidar processing across varied domains and sensor architectures. This approach not only achieves high performance in today's challenging multi-domain environments but also lays the groundwork for future innovations in sensor-agnostic perception systems.