Intro：3D sensing represents the main channel through which humans, or robotics agents, understand and interact with each other and with the real world. As such, many 3D acquisition technologies and devices have been developed and applied in emerging applications, such as autonomous systems, augmented reality and digital production. A typical 3D visual system takes RGB and/or range images of an object or scene and generates 3D geometry. There are several classic solutions for different settings, for example, structure from motion (SfM) for scattered images, Simultaneous Localization and Mapping (SLAM) for structured images along temporal axis. A research trend has been introducing deep learning into many conventional operations, such as pose estimation, spatial computation, and scene recognition. Besides 3D geometry, modeling of texture, material and lighting properties are also part of 3D visual processing.

Intro：Visual interaction is a kind of technology that defines mechanisms, through which the users can perform actions on the interactive system by means of visual elements, and the system can provide feedback to the user, by visually representing the results of the computations triggered by the user actions. It continues to be both a hot academic topic in computer science, and a key factor in industrial, medical, entertainment and office applications, etc. To achieve a more natural communication with human in a virtual environment (VE), we require to detect or recognize human face, emotion, gesture, eye gaze, etc., and to efficiently render high quality images, so that people can interact through natural interfaces and receive prompt and realistic visual feedbacks. Researchers attempt to create natural user interface (NUI) for human-computer interaction that the user operates through intuitive actions related to natural, everyday human behavior. Thus, most research focuses on traditional human abilities, such as vision, touch, motion, as well as cognition and even expert skills to replicate real world environments to optimize interaction between physical and digital objects. In this special issue, we have selected 7 papers (research articles) covering 3 most relevant visual interaction techniques for the VE applications, including facial expression and gesture recognition, real time rendering, 3D manipulation.

Intro：Virtual reality/augmented reality (VR/AR) has been widely used in the industrial fields, such as product design, manufacturing, assembly, maintenance, performance evaluation and other life cycle stages. The technical characteristics of VR can be summarized as virtual world, immersion, sensory feedback, and interactivity. The virtual world or virtual environment (VE) is a mapping of the real world. By reproducing the real environment, the operator can interact with the virtual world truly. For the research and application in the industrial fields, the modeling and simulation of the virtual world reflecting the physical nature are particularly important. The connection of virtual reality and real reality can be reflected in the expansion of two aspects from an industrial point of view: AR and digital twin (DT). On the one hand, AR technology reduces the workload of 3D modeling by integrating the virtual environment with the real world, and improves the credibility of the virtual environment and the experience of the operator. In particular, the term "augmented reality (AR)" was first proposed by Boeing in the early 1990s when they used the AR technology in auxiliary wiring systems. On the other hand, DT, one of the core technologies of the new generation of intelligent manufacturing, realizes the sharing of digital information through the mapping of the real and virtual worlds. In this special issue, we have selected 6 papers (4 review papers and 2 research papers) covering the most relevant technologies and fields in VR/AR/ DT applications, including cable layout design, digital human technology, target tracking, assembly guidance and virtual-real mapping manufacturing.

Intro：3D vision is a kind of technology that allow computers to perceive, reconstruct and interact with the 3D world based on vision sensors. It is not only a hot academic topic in computer science, but also crucial to many applications, such as virtual reality (VR) and augmented reality (AR). For achieving high-quality effects of VR and AR, we need to recover the 6DoF camera pose, 3D structure of the scene, and even the human interaction, so that people not only can see the lifelike virtual objects/scenes, but also the seamless fusion of virtual and real contents and even interact with them. We can leverage 3D vision technology to achieve this objective. For example, the simultaneous localization and mapping (SLAM) technique allows users to walk freely in a digital world wearing a VR/AR helmet by recovering the 6DoF movement of the helmet, and is also able to see the seamless mixture of real and virtual contents, and even the effect of their interaction with each other by reconstructing the geometry, textures and materials of the real environment. In this special issue, we have selected 6 papers (3 review papers, 2 research articles and 1 case report) covering 3 most relevant 3D vision techniques for the VR/AR applications, including SLAM, 3D reconstruction, object segmentation and tracking.

Intro：Human-computer interactions constitute an important subject for the development and popularization of information technologies, as they are not only an important frontier technology in computer science but also an important auxiliary technology in virtual reality (VR). In recent years, Chinese researchers have made significant advances in human-computer interactions. To systematically display China's latest advances in human-computer interactions and thus provide an impetus for the development of VR and other related fields, we have solicited articles for this special issue from experts in this area to participate in the review process. The following articles have been selected for publication in this special issue.

Intro：Touch is an important channel for human beings to communicate with the external world and plays a crucial role in human interaction with nature. Information such as softness, friction, texture and warmth, or more complicated human emotional communication can only be perceived by the act of touching. Despite its importance, it is striking that haptic feeback in human-machine interaction is still in its infancy. For example, a human user can enjoy realistic visual or auditory experiences facilitated by a computer through devices such as a head-mounted display or a stereo headset. However, haptic experiences that the user can obtain is extremely limited during such interactions. Haptic interaction technology enables users to touch virtual objects and experience tactile sensations, including contact force, softness, texture, weight, vibration, and temperature. These sensations can significantly enhance users' interactive experience of virtual-reality systems. Haptic interaction technology can be applied in many fields, such as surgical simulation/ training, virtual assembly and maintenance of complex mechanical equipment such as aircraft engines, interactive entertainment experiences such as movies and computer games.