SAC-GNC: Sample Consensus for Adaptive Graduated Non-Convexity

Outliers are ubiquitous in geometric vision contexts such as pose estimation and mapping, leading to inaccurate estimates. While robust loss functions can tackle outliers, it is challenging to make the estimation robust to the choice of initialization and to estimate the appropriate robust loss shape parameter that allows distinguishing inliers from outliers. Graduated non-convexity (GNC) often mitigates these issues. However, typical GNC uses a fixed annealing factor to update the shape parameter, which can lead to low-quality or inefficient estimates. This paper proposes a novel approach to adaptively anneal the shape parameter within a GNC framework. We developed a search strategy that incorporates a sampling of annealing choices and model scorings to select the most promising shape parameter at each GNC iteration. Additionally, we propose new stopping criteria and an initialization technique that improves performance for diverse data, and we show the benefits of combining discrete and continuous robust estimation strategies. We evaluate our method using synthetic and real-world data in two problems: 3D registration and pose graph optimization in SLAM sequences. Our results demonstrate greater efficiency and robustness compared to previous GNC schemes.