How 3D imagery of Dunhuang Silk Road cave paintings helps preserve Unesco site and shows murals in new light

Bernice Chan
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How 3D imagery of Dunhuang Silk Road cave paintings helps preserve Unesco site and shows murals in new light

For many people travelling along the route of the ancient Silk Road in China, the highlight is the Mogao Caves at Dunhuang containing the world’s most exquisite Buddhist murals.

Created between the fourth and 14th centuries, there remain more than 700 caves. Carved into the cliffs above the Dachuan River, in Gansu province, 492 of them are decorated with more than 45,000 square metres of murals and about 2,000 painted sculptures. Some show Buddhist imagery; others depict the daily lives of everyone from farmers to aristocrats.

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Not everyone can make the journey to Dunhuang, in the country’s northwest – and nor do they need to any more, thanks to work by the Dunhuang Academy and its collaboration with a number of scientific research institutions since the 1990s.

One such partnership has produced an exhibition at the Hong Kong Heritage Museum – “Digital Dunhuang – Tales of Heaven and Earth” – which showcases efforts to preserve the art of the Mogao Caves by using 3D technology to digitally scan them.

“The climate in Dunhuang is arid, [with] lots of sandy winds, so this environmental factor has long affected the safety of the murals and sculptures inside the caves,” says Fion Lin Hoi-yan, an assistant curator at the museum in Sha Tin, in Hong Kong’s New Territories.

“And also in recent years, there have been a lot of visitors to Dunhuang, and when they visit the caves it increases the temperature, humidity and carbon dioxide inside the caves, which affect the murals.”

The scanning process is tedious, and involves taking some 40,000 images per 300 square metres.

“The digitisation project is a challenging task because of the cave environment, such as poor lighting and uneven surface of the walls,” Lin says.

“After taking the scans of the images, they check the colour and clarity … and then they do post-production, stitching the images [together] on the computer. It is a difficult job to ensure the high quality of the images, which must have a 50 per cent overlap with other images to ensure the best quality.”

The results are stunning – highly detailed and accurate images of the caves. One room in the Heritage Museum, for example, is transformed into Cave 285, which is not open to the public in Dunhuang because it is one of the earliest and best preserved caves, dating to the Western Wei dynasty (535-557 AD).

Visitors can admire a precise copy and take in all the detail at their leisure. In Dunhuang, small groups view the murals with a small flashlight and have only a few minutes to gawk at the art.

The murals in Cave 285 have a palette of mostly blues, greens and terracotta, the brushstrokes still energetic, and the ceilings afloat with apsaras, or female spirits, flying in the sky in flowing robes.

The digitisation project is a challenging task because of the cave environment, such as poor lighting and uneven surface of the walls

Fion Lin, assistant curator at the Hong Kong Heritage Museum

The museum has used the digitised images to create interactive multimedia displays, and invites visitors to try to “catch” apsaras in flight, or see parts of murals in greater detail.

Looking closely at the image of Cave 285, Lin points out three deities. Two are from India: Ganesha, the elephant god, and Shiva, one of the principal deities in Hinduism. In another corner of the room, she points to Selene, the Greek moon goddess.

Dr Lee Chack-fan, director of the Jao Tsung-I Petite Ecole at the University of Hong Kong, advised the museum on staging the exhibition and training guides. He says Indian and Greek imagery from the caves illustrate how Dunhuang was at the crossroads of East and West.

“For more than a millennium, trade between East and West was largely conducted on the Silk Road on land; it’s not just one road – it’s a network of trade routes between East and West. There’s China at the eastern end, and west of China there’s India, the Roman empire, Mediterranean region, and then Central Asia and Xinjiang,” he explains.

Lee says the peak period for trade was between the fifth and ninth centuries during the Tang dynasty (618-907 AD). He adds that besides goods such as tea and silk being traded for jewels, carpets and metals, religions and cultures were also exchanged.

“There were monks who tried to spread their religious beliefs, not just Buddhist, but also Nestorian church – part of the Roman Catholic church based in Syria that spread Christianity to China through Dunhuang – and Persian Zoroastrianism,” he says.

“Dunhuang was basically the gateway to ancient China. All this would be reflected in the murals in the caves at Dunhuang. In the early years, you see the Indian influence in the murals, as well as Persian and Greco Roman.

“With time the murals become more and more in tune with Chinese artistic style. Not just the murals, but Buddhist statues, too.”

Lee, who trained as an engineer, first began visiting Dunhuang in the early 1980s with his wife, who is a Dunhuang researcher. In recent years he has been making bi-monthly trips to the caves as president of the non-profit group Friends of Dunhuang (Hong Kong), which raises funds to help preserve the caves.

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He recalls that more than 30 years ago the caves were quite run down. But thanks to donations from the organisation he leads, as well as from overseas, they are now in better condition.

“They [the Chinese] are very conscious of the importance of preservation. They limit the number of people who visit the caves, control the humidity and temperature to make sure the caves are best preserved. The conditions in the caves and Dunhuang in general are much improved,” he says.

Lee says the “cave temples”, as they are called, are a tradition from India, where monks would excavate caves for themselves to teach and meditate, and would decorate them with Buddhist-themed murals.

According to a book on the caves’ origin, An Account of Buddhist Shrines, written during the Tang dynasty, a monk named Le Zun had a vision of 1,000 Buddhas bathed in golden light at the Dunhuang site in 366AD, which inspired him to build a cave there.

Eventually other monks followed and the number of caves grew over the centuries. Some were carved out by fervent Buddhist believers, others created by artisans and paid for by wealthy families to commemorate them in perpetuity.

During the Tang dynasty, there were more than 1,000 caves. Construction had ceased by the Yuan dynasty (1271-1368), when the Mongols invaded China and Islam became more prominent in Central Asia.

It wasn’t until the late 19th and early 20th centuries that Western explorers became interested in the Silk Road and rediscovered the caves. Contemporary Chinese did not become interested in them until 1944, when the Kuomintang government set up the Research Institute of Dunhuang Art, later renamed the Dunhuang Academy, to safeguard the site. The Mogao Caves were declared a Unesco World Heritage Site in 1987.

The task of preserving the caves has since become a responsibility of the Dunhuang Academy. About seven years ago some 100 caves were singled out for special attention, and Lee’s non-profit group found sponsors for each of the caves, helping to raise funds to preserve and digitise their art.

Apart from the digital scans of the murals, the Heritage Museum is also displaying 36 artefacts that have never been seen outside mainland China before. They include part of a large stele carved with Chinese characters that documents the history of the caves, and scrolls with drawings of star constellations from the Tang dynasty.

“The Mogao Caves are a Buddhist art treasure, and also reflect the social life of the people over 1,000 years,” says Lin. “In the murals we can see a lot of social life, including what the people were wearing, what they were doing in their lives during that period. Apart from the treasure of Buddhist art, it is also an encyclopaedia of the Middle Ages.”

Lee says Dunhuang shows the interaction of different civilisations over the course of a millennium, and proves civilisations are interdependent.

“You will agree Buddhism is an important part of Chinese culture, but Buddhism came from India, it wasn’t a native religion. And the Buddhist statues carry a lot of Greco-Roman influence,” he says.

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“No civilisation exists in isolation, per se. They do intermingle with each other and influence each other. What we call Chinese civilisation today carries a lot of foreign influence.”

Digital Dunhuang: Tales of Heaven and Earth runs until October 22 at the Hong Kong Heritage Museum, 1 Man Lam Road, Sha Tin, tel: 2180 8188. Website:

This article How 3D imagery of Dunhuang Silk Road cave paintings helps preserve Unesco site and shows murals in new light first appeared on South China Morning Post

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