Semantic segmentation of point clouds of ancient buildings based on weak supervision

Semantic segmentation of point clouds of ancient buildings plays an important role in Historical Building Information Modelling (HBIM). As the annotation task of point cloud of ancient architecture is characterised by strong professionalism and large workload, which greatly restricts the application of point cloud semantic segmentation technology in the field of ancient architecture, therefore, this paper launches a research on the semantic segmentation method of point cloud of ancient architecture based on weak supervision. Aiming at the problem of small differences between classes of ancient architectural components, this paper introduces a self-attention mechanism, which can effectively distinguish similar components in the neighbourhood. Moreover, this paper explores the insufficiency of positional encoding in baseline and constructs a high-precision point cloud semantic segmentation network model for ancient buildings—Semantic Query Network based on Dual Local Attention (SQN-DLA). Using only 0.1% of the annotations in our homemade dataset and the Architectural Cultural Heritage (ArCH) dataset, the mean Intersection over Union (mIoU) reaches 66.02% and 58.03%, respectively, which is an improvement of 3.51% and 3.91%, respectively, compared to the baseline.