## 1 Introduction  
Visual comfort is a subjective evaluation of satisfaction with the surrounding environment [1, 2]. Today, people are increasingly pursuing satisfaction, especially satisfaction with the environment. Therefore, it is of practical significance to improve the ambient light condition [3]. As representatives of modern urban buildings, many libraries use full-transparent floor-to-ceiling windows, which allow people to observe from both inside and outside. While ensuring the aesthetic qualities of the building, this structure is relatively less considerate of visual comfort in the indoor environment. Individuals are more likely to suffer from extra glare [4].  
Based on current research, two main conclusions were derived from existing indoor lighting research. First, our research has shown that natural light technology can save 64% more energy compared to other institutions, so making full use of natural light can help protect the natural environment by making full use of natural energy [5, 6]. According to the available data, changes in library lighting conditions can affect users' reading, mood, comfort, and behavior in the library. Satisfaction and residence time are also affected by the light. With better sunlight, readers show more positive behaviour and favour lightened areas. Secondly, most of the current research has focused only on macro level concepts, such as form, function, space, the streamlined design of libraries and the form of future digital libraries. There have also been some related achievements in energy conservation research. Most of them are simple, producing findings on a macro level but have not conducted any specific spatial experience research. Most current studies are strategic analyses of natural light through simulation using a traditional calculating system. There is far less research that has conducted simulation analysis and collected quantitative data to propose improvements aiming at a more flexible light and climate environment. There are also relatively few studies on new shading devices and shading strategies based on light discomfort in college libraries. Thirdly, several studies have discussed the potential smart devices and automatic solutions for high-performance or efficient lighting environments, which inspired this research to take smart and automatic into consideration [7; 8; 9; 10]. The library is an important place for college students to carry out learning activities. Creating a comfortable indoor environment here is conducive to improving the overall experience and learning efficiency of students [11]. At present, this area of research, especially that focusing on design and practice, is relatively sparse worldwide [9].  
This project set Shanghai Jiao Tong University's main library as the research object. The college library we chose to study is one of the most frequently used learning spaces for teachers and students on the campus. The current library reading environment features obvious pain points in terms of visual comfort. Students and teachers bring their own umbrellas to block out strong sunlight, and seats close to the window are avoided due to strong direct sunlight. These forced actions obviously affect users' experience negatively. By focusing on the existing light environment of the library and the subjective experiences of users, this study pursues insights into existing pain points and real user needs and proposes corresponding design strategies that can improve the quality of the indoor environment of the library.