China
Africa
Explore chapters and articles related to this topic
Image-Based Lighting
Published in Francesco Banterle, Alessandro Artusi, Kurt Debattista, Alan Chalmers, Advanced High Dynamic Range Imaging, 2017
Francesco Banterle, Alessandro Artusi, Kurt Debattista, Alan Chalmers
where each term is equivalent to that in the plenoptic function for both the light and the view. When considering applications that make use of R, a number of approximations need to be taken into account. One popular application is the light stage and its various successors [110] (see Figure 7.19). These provide the ability of virtually relighting actors with arbitrary lighting after their performance is captured. The light stage captures the performance of an actor inside a rig surrounded by a multitude of lights.
Pattern Discovery from Eroded Rock Art
Published in Filippo Stanco, Sebastiano Battiato, Giovanni Gallo, Digital Imaging for Cultural Heritage Preservation, 2017
Filippo Stanco, Sebastiano Battiato, Giovanni Gallo
To construct PTM, we need to know the light position, including the lighting direction and distance between the light source and the rock surface. One simple approach is to build a light hemispheric cage with fixed-light positions. Automatic control of lights and camera can acquire a PTM with great speed, e.g., between 5 and 15 minutes. However, fixed-light position equipment has its disadvantages. The light distance from the subject limits the object diameter [33]. The bigger subjects require proportionally larger cage size and a more powerful lamp. To avoid using an elaborate light stage with a known light source position, the user may position a handheld light source at varying locations, and the software can recover the lighting direction from the specular highlights produced on a black sphere included in the field of view captured by the camera [33]. To measure and manage the light source radius, the “Egyptian Method” can be applied. This low-tech approach is to use one string with one end tied to the light source and another end tied to the center of the subject. Two people can hold each end straight. So the light distance is measured and the light held steady. A look-up table of distance-dependent light power values can help the field workers to change the string length and light power at the same time. The per-pixel surface normals are extracted from the representation to enhance the surface details. For example, specular enhancement. Simulation of specularity is particularly effective at enhancing the perception of surface shape. This is important to discover patterns in rock art. PTM requires only a single camera and a light for which the angle and distance can be measured. PTM is a low-energy technique that is desirable for field applications. This method has been used to discover a 3,000-year-old cuneiform tablet. The interactive texture map viewer is available online [19] and it has been popular in the archeologist community. Unlike photometric stereo or laser scans, PTM is implemented without the use of 3D geometry, eliminating 3D geometry’s associated costs in terms of hardware and software. However, PTM does not provide any depth information which is often useful to study the packing patterns.
Mobile phone use among e-cyclists at red traffic lights: An observation study in a city of China
Published in Traffic Injury Prevention, 2021
Jie Ni, Hongmao Qin, Xuanyi Liu, Yanjia Zhang, Zhiyun Tong, Jingwen Han
While age and mobile use were negatively correlated (Pearson correlation coefficient of −0.596). The age group was increased by one grade, the probability of mobile phone use was decreased by 44.9% (OR = 0.551, P = 0.000 < 0.001). Delivery e-cyclists were more likely to participate in mobile operations while waiting for red lights, and the probability of using mobile phones was more than 5 times as other e-cyclists (OR = 5.452, P = 0.000 < 0.001). Compared with the suburban intersections, the probability of mobile phone use in the city center was 37.0% lower (OR= 0.630, P = 0.040 < 0.05). Compared with off-peak hours, the use rate of mobile phones in peak hours was reduced by 45.6% (OR = 0.544, P = 0.003 < 0.01). The red light stage was positively correlated with mobile phone use (Pearson correlation coefficient of 0.466). The red light stage was increased by one level, the mobile phone use increases by 1.593 times (OR = 1.593, P = 0.000 < 0.001). And e-cyclists who carried a child were less involved in mobile phone use (OR = 0.313, P = 0.001 < 0.01).