Deep Learning for 3D Information Extraction from Indoor and Outdoor Point Clouds

This thesis focuses on the challenges and opportunities that come with deep learning in the extraction of 3D information from point clouds. To achieve this, 3D information such as point-based or object-based attributes needs to be extracted from highly-accurate and information-rich 3D data, which are commonly collected by LiDAR or RGB-D cameras from real-world environments. Driven by the breakthroughs brought by deep learning techniques and the accessibility of reliable 3D datasets, 3D deep learning frameworks have been investigated with a string of empirical successes. However, two main challenges lead to the complexity of deep learning based per-point labeling and object detection in real scenes. First, the variation of sensing conditions and unconstrained environments result in unevenly distributed point clouds with various geometric patterns and incomplete shapes. Second, the irregular data format and the requirements for both accurate and efficient algorithms pose problems for deep learning models. To deal with the above two challenges, this doctoral dissertation mainly considers the following four features when constructing 3D deep models for point-based or object-based information extraction: (1) the exploration of geometric correlations between local points when defining convolution kernels, (2) the hierarchical local and global feature learning within an end-to-end trainable framework, (3) the relation feature learning from nearby objects, and (4) 2D image leveraging for 3D object detection from point clouds. Correspondingly, this doctoral thesis proposes a set of deep learning frameworks to deal with the 3D information extraction specific for scene segmentation and object detection from indoor and outdoor point clouds. Firstly, an end-to-end geometric graph convolution architecture on the graph representation of a point cloud is proposed for semantic scene segmentation. Secondly, a 3D proposal-based object detection framework is constructed to extract the geometric information of objects and relation features among proposals for bounding box reasoning. Thirdly, a 2D-driven approach is proposed to detect 3D objects from point clouds in indoor and outdoor scenes. Both semantic features from 2D images and the context information in 3D space are explicitly exploited to enhance the 3D detection performance. Qualitative and quantitative experiments compared with existing state-of-the-art models on indoor and outdoor datasets demonstrate the effectiveness of the proposed frameworks. A list of remaining challenges and future research issues that help to advance the development of deep learning approaches for the extraction of 3D information from point clouds are addressed at the end of this thesis