The protection should not only pay attention to the ontology of the cultural relics of the Mogao Grottoes, but also pay attention to exploring the mechanism of the formation of cultural relics
The digitization of a complete mural requires thousands of photographs. The splicing is more complex, and the strands have to be "seamless". In recent years, with the development and application of 3D laser scanning technology, the accuracy and efficiency of cave data collection have been greatly improved
More than 6,500 high-definition digital archives from Mogao Grottoes and other grotto sites and Dunhuang scripture cave documents are open to the world
"Lookout" Newsweek reporter Song Changqing, Ren Yanxin, Zhang Yujie
Anyone who has been to the Mogao Grottoes will be amazed by its exquisiteness.
Excavated in 366 A.D., the Mogao Grottoes in Dunhuang have been built for more than 1,000 years after ten dynasties. Not only are more than 45,000 square meters of murals preserved here, but more than 60,000 cultural relics have been unearthed in the cave. In 1987, the Mogao Grottoes of Dunhuang were approved by the UNESCO World Heritage Committee to be included in the World Cultural Heritage List.
After thousands of years and being located in the desert, this treasure of human civilization will inevitably face wind and rain erosion. How to better protect and inherit the cultural heritage that has endured the vicissitudes of time is a common issue for all mankind.
Since the 40s of the 20th century, generations of Mogao Grottoes people have continued to relay and try to help the millennium Mogao Grottoes "beat the time" with the power of scientific research.
From wind prevention and sand control to disease cause analysis, from passive rescue protection to active preventive protection, the Dunhuang Academy has explored a relatively complete scientific protection system. Today, the relevant technology has been applied to more than 500 national key cultural relics protection projects in more than 20 provinces, autonomous regions and municipalities across the country.
At the same time, the digital technology of cultural relics has enabled the ancient murals of the Mogao Grottoes to come out of the dim caves and out of the desert Gobi, and realize global sharing, permanent preservation and sustainable utilization.
Keep the Mogao Grottoes
Known as the "palace of art in the desert", the Mogao Grottoes in Dunhuang are bordered by Sanwei Mountain in the east and Mingsha Mountain in the west, and are in the embrace of the desert.
It's windy more than half of the year. The sand that rises on the spot falls on the top of the Mogao Grottoes and accumulates on the plank road, which will also enter the cave, polluting and abrasive murals and painted sculptures.
Sand hazard control first began in the 40s of the last century. Cleaning up the sand in the cave area is one of the daily tasks of the first generation of Mogao Grottoes cultural relics conservationists such as Chang Shuhong, and 3,000 to 4,000 cubic meters of sand are removed every year. By building sand retaining walls, excavating sand ditches, and erecting sand fences, they began to explore feasible sand control measures, laying a solid foundation for the prevention and control of sand in Mogao Grottoes.
At the end of the 80s of the 20th century, the prevention and control of wind and sand hazards in Mogao Grottoes entered the stage of scientific research and control. The researchers installed a fully automatic weather station on the roof of the cave, and began to monitor the environment of the Mogao Grottoes area for a long time, especially the wind conditions, to find out the material source and migration characteristics of sand, to summarize the movement law of the Gobi wind and sand flow on the top of the cave, and to move from artificial sand removal to scientific management.
In 2008, the Dunhuang Mogao Grottoes Protection and Utilization Project was launched, in which the 13.81 million yuan investment in the Mogao Grottoes cliff top sand control project effectively alleviated the erosion of the Mogao Grottoes. In this comprehensive protection system, 1.14 million square meters of grass grid sand barrier and 1.19 million square meters of gravel sand compaction solve the problem of sand on the spot, 100,000 square meters of sand plant plantations with wind and sand fixation, and 6,000 meters long high vertical nylon mesh fence form the final protection. The project was completed in 2011.
Monitoring data shows that after the implementation of the project, the annual amount of sediment entering the Mogao Grottoes area has decreased by 85% compared with before the implementation.
The Mogao Grottoes, which no longer "go down to the sand" throughout the year, have changed their appearance, and the green area has gradually extended from a small area to the north. In the middle of summer, the forest in front of the cave area is lush.
The number of tourists has increased year after year, which has brought new issues to the protection of cultural relics in Mogao Grottoes.
In the Dunhuang Grottoes Monitoring Center of the Dunhuang Academy, the temperature, humidity, carbon dioxide concentration, passenger flow and other data of each open cave are being displayed on a large screen on a whole wall, and even the rainfall, flood, and sand conditions within a few hundred kilometers are also updated in real time on the big screen.
This preventive protection monitoring and early warning system relies on more than 600 different types of sensors placed in the cave area to realize the real-time collection and interactive analysis of data such as the general environment of Mogao Grottoes, the micro-environment of the caves, the ontology of cultural relics, the cliff body, the exhibition and the carrying capacity of tourists. It provides reliable data support for preventive protection while providing timely warning of potential risks.
"If we find that the monitoring data such as relative humidity and carbon dioxide in the cave exceed the warning value through the system, the cave will be closed and naturally ventilated, so as to ensure the safety of the cultural relics to the greatest extent. Chai Pengfei, assistant librarian of the Dunhuang Academy, said.
The protection should not only pay attention to the ontology of the cultural relics of the Mogao Grottoes, but also pay attention to exploring the mechanism of the formation of cultural relics.
At the end of 2020, after years of construction, the National Engineering Technology Research Center for the Protection of Ancient Mural Paintings and Earthen Relics was put into operation in Dunhuang. "Multi-field coupling, in short, is the simultaneous simulation of many different environmental conditions. Guo Qinglin, vice president of the Dunhuang Academy, said.
In the experimental chamber, large earthen samples weighing several tons were placed. The staff operates the equipment, and various meteorological conditions such as wind, rain, snow, and sun exposure can be simulated in the experimental warehouse. A series of temperature and moisture content sensors were laid in the middle layer of the sample to monitor the influence of temperature and rainfall changes on the deterioration of the sample, in order to reveal the development mechanism of weathering diseases on the surface of the soil site.
According to reports, the multi-field coupling laboratory has the advantages of controllable time, controllable variables, repeatable conditions, and full-scale model tests. Cultural relics conservators can reveal the development mechanism of diseases through experimental research, and then verify the protection and reinforcement technology, so as to take corresponding protection measures. The research results from the multi-field coupling laboratory will also be put into the protection and application of cultural relics in different environments across the country.
In Cave 55, which is being protected and repaired in the Mogao Grottoes in Dunhuang, cultural preservation workers sort out the collected data (taken on August 3, 2023) Photo by Li He/This Magazine
Rebuild the Mogao Grottoes
In the exploration of the digital preservation of colored sculptures and murals, Mogao Grottoes is at the forefront.
In the 80s of the last century, the cultural relics workers of the Dunhuang Academy saw the comparison of photos before and after the erosion of the Mogao Grottoes, and realized the necessity of digital preservation.
At the end of the 80s of the last century, the Dunhuang Academy tried for the first time to use computer digitization technology to permanently preserve precious materials such as Dunhuang murals and colored sculptures. Antiquities workers entered the cave and set up their camera cameras in front of the mural. Initially, they used Kodak film to take photos, processed them, and later used high-fidelity digital cameras to shoot them, and then used computer technology to stitch them back. It took 20 years from the idea to the actual high-fidelity digital archive.
Due to the special structure and layout of the grottoes, and the fact that many cultural relics protection principles must be observed, the digitization process of Dunhuang cultural relics is complicated. When collecting images, personnel carefully move around in the cramped space of the cave to ensure that the murals will not be harmed; after entering the cave, they must constantly measure the light to avoid shadows in the final image; and they must use a constant temperature cold light source to minimize the impact on the cultural relics themselves......
After the collection is completed, the photos are also stitched together and restored to a high-fidelity mural drawing. The splicing error should be controlled at the millimeter level, and the hair strands should be "seamless".
"A mural of more than ten square meters needs to take thousands of photos. Stitched together, the digitally generated wall is four times the size of the original, making it much clearer on screen than in a cave. Yu Tianxiu, director of the Institute of Digitization of Cultural Relics of Dunhuang Academy, said.
In recent years, with the development and application of 3D laser scanning technology, the accuracy and efficiency of cave data collection have been greatly improved. The image accuracy has been increased from 75DPI to 300DPI, and the processing capacity has been increased from one or two caves a year to twenty or thirty caves a year......
By the end of 2022, the Dunhuang Academy has completed the digital photography collection of 289 caves, the image processing of 178 caves, the 3D reconstruction of 45 painted sculptures, 140 caves, and 7 large ruins, the production of panoramic roaming programs for 162 caves, and the digitization of more than 50,000 archival negatives.
At the same time, the Dunhuang Academy continues to promote the application of digital achievements of cultural relics, serving archaeological research, cultural relics protection, and mass communication.
In 2014, with the trial operation of the Mogao Grottoes Digital Exhibition Center, the 8K dome film "Dream Buddha Palace", which revitalizes the digital resources of Dunhuang cultural relics, was launched. This 20-minute film showcases the 7 classic caves of the Mogao Grottoes in an all-round way. The audience sits in the theater, as if they are in a real scene, and they can see it more clearly than visiting the Mogao Grottoes.
In addition to "Dream Buddha Palace", the Dunhuang Academy also produced the theme film "Millennium Mogao". Fan Jinshi, honorary president of the Dunhuang Academy, said: "Before arriving in Dunhuang, tourists can watch these two films at the Mogao Grottoes Digital Exhibition Center to understand the historical and cultural value of Dunhuang, and then enter the physical caves to visit, and the experience will be better." ”
Spread the Mogao Grottoes
At the end of 2022, the world's first blockchain-based open sharing platform for digital cultural heritage, "Digital Dunhuang Open Material Library", was officially launched, and more than 6,500 high-definition digital archives from Mogao Grottoes and other grotto sites and Dunhuang scripture cave documents were opened to the world.
"In the past, the old gentlemen were doing research in the Mogao Grottoes, and the caves were all black, and the words on the list could not be read clearly. So they set up ladders and took flashlights and binoculars to reach for them. Yu Tianxiu said. Now, scholars and culture enthusiasts from all over the world can browse ultra-high-resolution images of the cave at high speed with just a few clicks from their homes.
On the "Digital Dunhuang Open Material Library" platform, each high-definition image is the first-hand information generated after the digital collection of the Mogao Grottoes, and each image is annotated with a corresponding academic introduction. "The material library realizes the effective use and sustainable development of digital resources of cultural relics in an open, co-creation and sharing mode. Su Bomin, president of the Dunhuang Academy, said.
In April 2023, under the guidance of the State Administration of Cultural Heritage, the "Digital Scripture Cave" was also officially launched. This "immersive" online museum uses digital scanning, 3D modeling and other technologies to reproduce the Dunhuang scripture caves with high precision.
The "Digital Scripture Cave" strives to be "fun". Users only need to log in to the "Cloud Tour Dunhuang" applet to enter the high-definition restoration of the Tibetan scripture cave, watch the details of the cave up close, and also travel to different eras to interact with historical figures through character role-playing, and "experience" the changes in the appearance of the Tibetan scripture cave from the late Tang Dynasty to the late Qing Dynasty.
From the "Flying Sky" special tour route to bring people the experience of combining virtual and real, to the online interaction of more than 200 million people participating in the "Cloud Tour Dunhuang" WeChat mini program, to the advent of the virtual human "Jia Yao...... In the "cloud", Dunhuang culture is interconnected with a wider range of audiences in a richer form through information technology.
Offline, Dunhuang's cultural relics protection technology is also further enhancing its influence around the world.
As the world's largest scientific research institution for the protection of cave temples, the Dunhuang Academy has leading advantages in the protection of murals, earthen sites, digital research of cultural relics, and open utilization. A large number of its innovative achievements have been popularized and applied to more than 500 national key cultural relics protection projects in more than 20 provinces (regions) such as Gansu, Tibet, Xinjiang, Ningxia, Qinghai, Shanxi, and Hebei.
The cultural relics protection model of "Dunhuang Experience with Chinese Characteristics" represented by the Dunhuang Grottoes has been basically formed, and its influence has spread to Afghanistan, Nepal, Uzbekistan, Kyrgyzstan and other countries that jointly build the "Belt and Road".
The Dunhuang Academy also contributes to the cultivation of cultural relics conservation talents around the world. Su Bomin introduced that the Dunhuang Academy has successively carried out various forms of exchanges and cooperation with more than 30 institutions in more than 10 countries and regions such as the United States, Japan, the United Kingdom, Australia, France, and more than 40 domestic scientific research institutes and colleges and universities, explored the scientific protection of cultural heritage in an all-round way, and cultivated a large number of professional and technical personnel and management talents in the digital protection of grottoes, murals, earthen sites and cultural relics.
"Heritage conservation is always on the way. Su Bomin said that in the future, he will continue to focus on the major needs of the international frontier and the field of national cultural heritage protection, take the scientific protection and effective utilization of cultural heritage as the mission, actively carry out international cooperation and exchanges with the countries that jointly build the "Belt and Road", continuously promote the promotion and application of research results, and strive to create a new situation in the protection, research and promotion of cultural heritage.