Neighborhood Spatial Aggregation MC Dropout for Efficient Uncertainty-aware Semantic Segmentation in Point Clouds

TL;DR

This paper introduces NSA-MC dropout, a novel method for efficient uncertainty-aware semantic segmentation of point clouds that achieves faster inference and reliable uncertainty estimation by aggregating neighbor information in a single pass.

Contribution

The paper proposes NSA-MC dropout, a space-dependent sampling method that significantly speeds up uncertainty estimation in point cloud segmentation without sacrificing accuracy.

Findings

NSA-MC dropout is several times faster than traditional MC dropout.

The framework improves segmentation accuracy on real-world point clouds.

It effectively quantifies predictive uncertainty, aiding in model confidence assessment.

Abstract

Uncertainty-aware semantic segmentation of the point clouds includes the predictive uncertainty estimation and the uncertainty-guided model optimization. One key challenge in the task is the efficiency of point-wise predictive distribution establishment. The widely-used MC dropout establishes the distribution by computing the standard deviation of samples using multiple stochastic forward propagations, which is time-consuming for tasks based on point clouds containing massive points. Hence, a framework embedded with NSA-MC dropout, a variant of MC dropout, is proposed to establish distributions in just one forward pass. Specifically, the NSA-MC dropout samples the model many times through a space-dependent way, outputting point-wise distribution by aggregating stochastic inference results of neighbors. Based on this, aleatoric and predictive uncertainties acquire from the predictive distribution. The aleatoric uncertainty is integrated into the loss function to penalize noisy points, avoiding the over-fitting of the model to some degree. Besides, the predictive uncertainty quantifies the confidence degree of predictions. Experimental results show that our framework obtains better segmentation results of real-world point clouds and efficiently quantifies the credibility of results. Our NSA-MC dropout is several times faster than MC dropout, and the inference time does not establish a coupling relation with the sampling times. The code will be available if the paper is accepted.