LAGD: Local Topological-Alignment and Global Semantic-Deconstruction for Incremental 3D Semantic Segmentation

Numerous deep learning-based works focusing on 3D semantic segmentation have been proposed and have achieved impressive performance. However, due to the catastrophic forgetting, existing methods will degrade dramatically in a real-world scenario where new 3D semantic categories are arriving continually. Straightforwardly applying typical class-incremental learning methods on 3D data even aggravates forgetting due to the irregular and noisy geometric structure. Aiming to address this realistic challenge, from the perspective of capturing local topological characteristics and mitigating global semantic shift, we propose a unified framework named Local topological Alignment and Global semantic Deconstruction (LAGD) to incrementally learn semantic knowledge of novel 3D categories while maintaining performance on previously learned knowledge. Specifically, we develop a novel Interaction Topological-aware Alignment (ITA) to maintain the learned knowledge efficiently by capturing the local geometric characteristics with interacted adjacent state-specific knowledge. Besides, to mitigate the forgetting caused by the global semantic shift, we deconstruct the logits into positive and negative parts which are distilled separately, achieving an elaborate distillation process in terms of Semantic-knowledge Deconstruction Distillation (SDD). With the cooperation of ITA and SDD, LAGD achieves a sota performance, especially in the long-term incremental learning scenario. Extensive experimental results illustrate the superiority of our proposed LAGD.