A digital and immersive experience of the cave. [Photo provided to China Daily] More than a century after the Mogao Grottoes were discovered, it is a hard task saving them from the ravages of man and nature. In 1900 a Taoist priest named Wang Yuanlu found a cave in Dunhuang, Gansu province, packed with tens of thousand of volumes of Buddhist sutra. Six years later the Hungarian-British archaeologist Marc Aurel Stein arrived in Dunhuang followed soon after by the French archaeologist Paul Pelliot. Both paid a pittance for priceless treasures from the cave, and both took photos of it and its surroundings. When you compare those photos and ones taken recently, the extent of the irretrievable cultural losses that Dunhuang and the world have suffered over the past century or so becomes clear. Colors on many of the murals and statues have faded, and blurry areas have become more expansive as a result of oxidation and human-inflicted damage. Such damage happened in the 1950s and 1960s when artists tried to make facsimiles of murals, when archaeologists tried to survey and map the caves, or in recently years when the growing number of tourists increased the quantity of carbon dioxide and humidity and the exposure of the relics to light or other elements that can speed up their deterioration. In an effort to minimize the risk of damage, visitors have had to apply online to visit the caves since last July, and the number of visitors is limited to 6,000 a day. Before beginning their tour proper, visitors need to go to Mogao Grottoes Visitor Center to watch two 20-minute high-definition movies about the grottoes, including a film about the seven most valuable caves in terms of artistic achievement.
Cameramen use scaffolding to capture the images on the irregular shaped roof [Photo provided to China Daily] Since the end of last month it has been possible for people around the world to watch online 3-D views of the caves, and virtual reality devices can be used to view the images. "Over the past three decades, especially in recent years, we have been developing digital technology that can be used not only to preserve detailed image materials about the relics, but also to help archaeologists record the finest information about the caves, and to help artists make facsimiles of the murals," says Wu Jian, director of the digital center of Dunhuang Academy, a research institute devoted to studying and preserving the Mogao Grottoes. Cai Weitang, 59, an archaeologist, joined the academy in 1978. He is among the first to apply the digital technology in his work. Earlier, all the field surveys and mapping were done by hand, Cai says. "We had to erect scaffolding so we could measure the higher parts of the caves." A typical old-fashioned tool case for an archaeologist in Dunhuang includes a compass, a tape, a set square, a steel tape, a plummet and a home-made square grid. The grid, usually one or two meters long, consists of a handful of lines, fixed horizontally and vertically to form small squares of about 1 square centimeter. In the past, when surveying and mapping a mural, Cai put the grid in front of it without touching it. For example, if he planned to copy the lines of an eye on the picture, he would find three points on the grid, jot them down and connect them with lines. In this way, you could slowly build a collection of the outlines of the murals and colored statues.
3-D point cloud technology helps photographers to have a better rendering of the murals [Photo provided to China Daily] Apart from keeping accurate records of the murals and statues, archaeologists need to do the same for the caves, including taking high-definition photos, so that if one day the caves are destroyed for any reason, records will yield enough information that will allow the Mogao Grottoes to be fully and accurately replicated. After Cai drew all the lines on the gridded paper the lines needed to be copied onto imitation parchment for publication. "It's an extremely complex job, and very time-consuming," he says, adding that there were too many inaccuracies measuring with rudimentary tools. "People draw differently. Some are good, some bad. They have very different styles." Dunhuang Academy was founded in 1944 by Chang Shuhong. At the very beginning, the older generation planned to take care of the archaeological records, but until the 1990s the project was behind schedule. It planned to publish 100 volumes of archaeological record of this UNESCO World Heritage site, covering everything in the Mogao Grottoes, and the nearby Yulin Grottoes and Western Thousand-Buddha Cave. The first of the 100 volumes published in 2011 includes caves numbered from 266 to 275. Generally using the old way of surveying a cave would take two to three people five to six years. "We will be able to finish all the surveying and mapping in four years thanks to 3-D point-cloud scanning technology," Cai says.
3-D printed Buddhist sculptures [Photo provided to China Daily] This technology enables users to collect detailed information of the subject based on many points chosen during scanning, so that the detail of a curved surface or complicated structure and lines can also be captured. It takes the scanner one to two hours to finish scanning a whole cave. After scanning, processed digital information generates the cave's structure drawing and the outline of the statues directly. But the shape of eyes and noses on murals do no reproduce clearly, so archaeologists need to revise the drawing relying on high-definition photos. "It's our first try," Cai says. "The new method cuts the work time by one third, and it's much more accurate." At the moment a reproduction of Cave 320 of the Mogao Grottoes is on display at the Getty Center in Los Angles. The exhibition, which opened in May, will continue until September. Ma Qiang, 53, director of the academy's fine art institute, is one of the artists taking part in the project. He spent four years creating facsimiles of the 6-sq m mural on the eastern wall of Cave 320. Since 1981 when the 17-year-old Ma first arrived at Dunhuang Academy after failing the national college entrance examination, he has finished facsimiles of more than 30 pieces of murals in the Mogao Grottoes.
Dunhuang Academy now uses high-resolution cameras to capture the images of the murals. [Photo provided to China Daily] Slide projector In the 1950s the State Bureau of Cultural Relics received an old-fashioned slide projector from Poland as a gift, Ma says. Zheng Zhenduo, then head of the bureau, gave the projector to the Dunhuang Academy. Ma recalls that the projector was still being used in the 1980s. If artists at that time wanted to create a facsimile of a mural they would first go to the cave to use rulers to measure its dimensions and record the information in notebooks. Photographers from the photographic section that later became the digital center would take 10 black-and-white photos of the mural from beginning to end. "I would get the negative films of the 10 photos, and then I took the projector and the films to bigger caves like No 61 or 98," Ma says. After setting up a board and spreading two layers of Chinese art paper on it, Ma turned on the projector and put the films on it. The shadow of the films were then projected onto the paper. The size of the shadow could be adjusted according to the size Ma measured in the cave. With the mural's details on paper, Ma was able to trace the lines－even broken or unclear ones－and draw them on the paper, because "we had to take down all the information", he says. However, after the projector had been on for 30 to 40 minutes the films would become too hot and would become deformed. So he then had to take a break to wait for the projector to cool and the films to return to their original state. Ma would later go back to the caves to see what lines had been completely missed out or were incorrectly shown. Usually, it would take an artist a year to do the first draft and revise it, and another year to color it. "The more important thing is to understand the spirit of those murals and how their unique style developed in different historical periods," Ma says.
A painting portraying Mogao Grottoes in Dunhuang [Photo provided to China Daily] Different styles Sometimes the same Buddhist stories are presented in different styles. Ma cites the classic Buddhist story about a prince who sacrifices himself to feed tigers. Cave 428 and Cave 254 have murals that present the story, but the one in Cave 254, completed during the Northern Wei Dynasty (AD 386-557) is more in the Han ethnic style, looking more unrestrained and free, compared with that in 428, drawn during the Tang Dynasty (AD 618-907), which is more ornamental, Ma says. Because of the complicated procedure, copying a 6-sq m mural would take two to three people two years to complete. "Now it's easier for me to do a copy," Ma says. "But I have a lot of other work to do, and It took me four years, from early 2012, to finish doing the facsimile of the mural on the east wall of Cave 320. I had to do the management work, write papers and do my own artistic works. Last year he completed 500 ink and wash paintings. "This time we used 3-D point-cloud technology to collect the digital information of the whole cave. Based on that we can build a wooden model of the cave and draw the outline of the murals."
A painting portraying Mogao Grottoes in Dunhuang [Photo provided to China Daily] Technology Based on the outlines produced by the technology and the high-definition photos provided by the digital center, artists fill in colors made of special stone such as turquoise, malachite and cinnabarit, and add finer lines that have been missed by the scanner. "We still need to go to the caves to see the original murals and study their history and artistic styles so we can understand the spirit of the works in those years," Ma says. The high-definition photo sometimes can be misleading to inexperienced artists. "They focus too much on the broken or missing parts, and overlook the whole," Ma says. Wu says the focus of future work at the digital center will be on studying how to present the digital information collect to audiences. Ma believes artists' work being based on 3-D printed copy works of the murals will become the norm. In June, the Dunhuang Academy presented the 3-D printed Buddhist sculptures and their holographic images at the recent 12th Five-Year Plan Scientific Innovation Exhibition in Beijing attracting a lot of attention. "If the new technology can do the job, we will let it do. We artists do what it cannot, such as adding to the thickness and granular sensation of the copies." |
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