Application of Virtual Reality technology in Cultural Heritage Conservation - Dr. Qiao Mu
Abstract: This paper analyzes the development process and main technical characteristics of virtual reality technology from the prominent problems existing in the protection of cultural relics in China at present, and deeply studies the application and key technologies of virtual reality technology in the protection of cultural relics, and analyzes the Mogao Grottoes as an example.
Keywords: Virtual reality technology; Conservation of cultural relics; Historic buildings;
I. Status quo of cultural relics protection in China
China has a large number of cultural relics, but more than 50% of them have been damaged, such as paper, lacquer, embroidery and other cultural relics have been damaged to varying degrees in the process of inheritance, resulting in embrittlement and decolorization. In the past, only restoration and copying were carried out, which failed to prolong the life of cultural relics and cost a lot of money, time and manpower. In addition, a large number of immovable cultural relics are located in remote areas, so relevant workers cannot protect them well and cultural relics cannot give full play to their core values .
Some scholars' statistics show that China's existing cultural relics exhibition sites up to hundreds of thousands of places, tens of millions of various cultural relics, China has a large number of cultural relics, but only a small part of the cultural relics are exhibited for the public to learn and visit. The Nanjing Museum, for example, has a collection of up to 400,000 cultural relics, of which only 2% are on display. At the same time, in the process of cultural relics exhibition , a large amount of human, material and financial resources should be invested to protect cultural relics and professional protection measures should be taken. Cultural relics exhibition is difficult to change frequently, the same group of cultural relics exhibited for a long time, it is difficult to attract the public to visit, so it leads to a vicious circle, which is not conducive to the function of museums and the development of cultural relics protection.
The protection of cultural relics in China is faced with the dual influence of natural factors and human factors. Firstly, in terms of natural factors, global warming, bad weather, economic growth and other factors will have an impact on cultural heritage. Secondly, in terms of human factors, fire, war, smuggling and excessive tourism have also increased the difficulty of cultural relic protection. For example, some cultural relics were lost overseas , which made it impossible to appreciate or visit a complete cultural heritage. For example, the Old Summer Palace became ruins in numerous catastrophes. While the rapid development of tourism has brought local economic income, it has also brought many restrictions to the protection of some cultural heritage. Some regions have not invested enough in the protection of cultural relics. For example, the ancient city of Pingyao collapsed three times in just two years.
Second, virtual reality technology analysis
2.1 Development of virtual reality technology
Virtual reality technology, referred to as VR technology, is a technology widely concerned by engineering and scientific circles in the 1990s. Virtual reality technology has created a new research direction in the field of human-computer interaction interface, is an important application field of intelligent engineering, and provides a new technical means for data visualization of large-scale engineering. Using virtual reality technology, by virtue of the storage and computing advantages of computers, virtual three-dimensional space can be constructed, realistic virtual simulation can be realized, and users can have an immersive visual experience. As early as 1965, some scholars put forward the basic idea of virtual reality system. Then Lincoln Laboratory in the United States began to develop helmet display, and integrated haptic force feedback system and simulated force system model into the display system. Based on the above theoretical and technological breakthroughs, the word VR (Virtual Reality) was formally proposed in the 1980s. Virtual reality technology was first applied in the DEPARTMENT of Defense and NASA of the United States, and achieved satisfactory results. Later, several general sensing virtual reality technologies and simulators were developed . In the 1990s, the rapid development of computer hardware and software system made it possible for the commercial application of virtual reality technology, and general-purpose INPUT and output devices were introduced continuously.
2.2 Main technical characteristics of virtual reality
Virtual reality technology mainly includes virtual real scene technology and virtual virtual scene technology, which has been widely used in many fields. Virtual reality technology includes the following four main technical characteristics: ① strong sense of presence. With the help of virtual reality technology, users can experience the sense of reality in the simulated environment. ② Excellent interactive performance. The ability of users to manipulate objects in a simulated environment and the degree to which they can get feedback from the virtual environment is called interactivity. With the help of mechanical sensing equipment, users can experience the tactile sensation of grasping objects in the real environment in virtual reality, and objects can also move with the movement of hands. ③ Multi-sensory ability. In the virtual reality scene, users can not only have visual feelings, but also realize tactile, force, hearing, taste and other sensory abilities. In the ideal virtual reality scenario, users can feel the same perceptual function as the real scene. ④ Autonomy. Autonomy requires the construction of physical motion laws similar to those in real scenes to make them conform to mechanical laws. When a force is applied to an object, it will move or topple in the direction of the force. In a closed-loop virtual reality scene, it can be connected with the user in the virtual environment through the sensor .
The application of virtual reality technology in the protection of cultural relics
3.1 The role of virtual reality technology in cultural relic protection
3.1.1 Improve the protection effect
With the help of virtual reality technology, the problems of oxidation, weathering and destruction of cultural relics can be avoided in the protection and exhibition of cultural relics, and cultural relics can be protected to the maximum extent. By means of image and virtual scene, the restored cultural relics are displayed in the best state, and the best way of cultural heritage protection is selected at the same time. For large cultural relic buildings, virtual reality technology can build three-dimensional virtual scenes, presenting users with an immersive feeling.
3.1.2 Break through time-space limitations
As a digital way of storage and information transmission, virtual reality technology can greatly break through the limitation of time and space. In this process, cultural relics from a long distance are moved to the observer without environmental and regional restrictions, so as to avoid damage of cultural relics in the process of moving. More importantly, virtual reality technology has broken the model of museum exhibits, allowing users to "visit" anywhere 24 hours a day via the Internet.
3.1.3 Diversified display methods
With the powerful display function of virtual reality technology, it can provide the public with more diverse ways of observation and feeling. First of all, small cultural relics can be displayed in a three-dimensional way from multiple angles, changing the traditional way of observer moving and cultural relics stationary to the way of cultural relics moving and observer stationary, thus improving the observation experience. Secondly, for large stone carvings or ancient buildings, virtual reality technology can construct a virtual scene to help observers enter a relatively independent historical space and enrich the observation perspective and experience .
3.2 Implementation process of virtual reality technology to protect cultural relics
3.2.1 Obtaining Data
In order to restore cultural heritage more truly and provide a more realistic virtual environment, it is necessary to obtain high-precision THREE-DIMENSIONAL data by means of multiple measurement methods. The commonly used measurement techniques include instrumental measurement, lidar measurement, photogrammetry, etc. To measure cultural heritage in large scenes, instrument measurement technology is mostly adopted, and the use of total station can easily complete the collection of large range of data. Regular geometry or super large stone carvings, photogrammetry technology can be used to accurately obtain three-dimensional data; For cultural relics with irregular surfaces or complex shapes, laser scanning technology is the most convenient and the data collection accuracy is higher . Usually, one or two measurement techniques can be used to complete data collection of different cultural relics in cultural heritage.
3.2.2 3D modeling of virtual environment
On the basis of obtaining accurate 3D data, 3d modeling of virtual environment is the key step to realize virtual reality technology, and is also the basic work of digital online protection of cultural relics. At present, mature modeling software is often used in 3D modeling to complete the interactive modeling process of object cultural relics, and the modeling accuracy is high. The use of modeling software can avoid heavy manual operations, high modeling efficiency, high degree of automation, but it should also be noted that the mold accuracy and cost show a positive correlation, each step of modeling accuracy, accompanied by a large increase in capital investment.
3.2.3 Generate real-time 3D graphics
The most convenient way to display the built 3D scenes or models of cultural relics in front of users is to use 3d graphics generation technology. In the process of generating real-time station graphics, the key is to realize the real-time reproduction of 3D images, requiring that the frame rate should be higher than 30 frames per second. In the process of using this technology, the biggest technical difficulty is to improve the frame rate of graph drawing as much as possible on the basis of guaranteeing data quality and graph complexity.
3.2.4 Sensor and stereo display technology
Simple screen display cannot give full play to the maximum value of virtual reality technology in the protection of cultural relics. At present, many researchers propose to use sensor technology and stereoscopic display technology to bring real tactile sensation to users under the condition of non-touch. A variety of head-mounted displays developed by using sensor technology, combined with data gloves or clothing, combined with pressure technology and mechanics principle can provide a more real virtual scene. At the same time, compared with simple screen display, large three-dimensional display equipment in virtual tourism shows a more vigorous vitality and market demand.
3.3 Application key system tools
In the process of applying virtual reality technology to cultural relics protection, we should first analyze the best technology matching for the cultural relics, and develop the corresponding system tools, commonly used technologies include distributed virtual reality technology and virtual reality system development platform. The core technologies to realize virtual reality include the following: (1) Real-time 3D computer graphics technology, which can generate accurate images of the target cultural relics in different environments, its focus is on real-time and high precision; (2) wide field stereo display technology, with the help of wide field stereo display technology, users wearing special glasses, can display odd frames of images in one eye, the other eye display even frames of images, that is, the visual sense of stereo; (3) The sound brought by stereo playback technology greatly improves the reality of virtual reality; ④ Haptic feedback technology is equipped with vibration contacts in special gloves to provide tactile and mechanical feelings.
3.4 Application cases of virtual reality technology in cultural relic protection
Taking Dunhuang Mogao Grottoes as an example, this paper discusses the application of virtual reality technology in the protection of cultural relics. Dunhuang Mogao Grottoes is a cultural and artistic treasure in northwest China. It is located at the key point of the Silk Road, and its cultural relics are the treasures of Chinese and Western civilization. Mogao Grottoes has suffered from earthquake, sandstorm, theft, painting and other damage in the history of more than one thousand years. In addition, the excessive tourism development in recent years has caused almost all the caves in mogao Grottoes to have different degrees of cultural relics destruction. In recent years, Dunhuang Academy has done a lot of work in the protection of cultural relics, and has achieved good protection effect on the existing murals, buildings and painted sculptures . However, it should also be noted that the mogao Grottoes cultural site is old and large-scale, and the amount of protection works is huge. At the same time, many difficulties in the protection of murals have not been completely overcome, which brings many difficulties to the protection of cultural relics. The protection of cultural relics in Dunhuang Mogao Grottoes mainly includes three objectives. First, it is necessary to complete full 3D modeling of 482 caves and the surrounding area of more than 230 square kilometers of Mogao Caves. The scope of modeling includes indoor cultural relics and outdoor environment, construct high-precision reproduction archives, and build a platform for the application of virtual reality technology. This foundation work can not only be used by visitors, but also provide a convenient tool for cultural heritage conservation and reconstruction research. Secondly, the existing frescoes are reconstructed and chromatically restored. Finally, based on the above two achievements, the historical stories of Dunhuang frescoes are restored and 3d interpretation of virtual reality technology is carried out. The application of virtual reality technology in the protection of cultural relics in Mogao Grottoes is mainly embodied in digital Dunhuang Project. Introducing a new generation of digital technology and information technology in dunhuang heritage protection, the existing and relevant cultural relics including dunhuang caves, sculptures, murals, buildings, etc., to generate images with high resolution, combined with the digital technology, the dunhuang cultural relics related literatures and results of the study are compiled into electronic archives, by means of laser scanning photography, aviation photographs, The whole 3D data and image data inside and outside the Dunhuang Mogao Grottoes are obtained to establish the 3D visual digital environment model. Through the above three aspects of work, we can not only protect the precious sculptures and murals, but also reproduce the models of mogao Grottoes by virtual reality technology for browsing, visiting and research. The specific workflow analysis is as follows: ① With the help of high-precision photography and laser scanning technology, obtain indoor and outdoor environmental data; (2) Make contour map and orthophoto map and establish 3d database; (3) Based on the above data, 3d data modeling is carried out, including data acquisition, irregular triangulation network construction, 3d restoration model construction; (4) Finish texture stitching and detail characterization in the above model .
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