More than 150 years ago, a large imperial garden known as Yuanmingyuan lay in the northwestern outskirts of Beijing. Its exquisite buildings and massive collection of valuable artworks earned it the title of "Garden of Gardens" before it was looted and set on fire by Anglo-French allied forces in 1860 during the Second Opium War (1856-60). But the tragedy wasn't over. It suffered further damage after allied forces of Britain, France, Germany, Tsarist Russia, the United States, Japan, Italy and Austria occupied Beijing in 1900 and subsequently fell into ruins.

Reproducing the excellent scenery of Yuanmingyuan has been a dream for generations of Chinese architects including Guo Daiheng, an 80-year-old professor at the School of Architecture of Tsinghua University. In April, a team led by Guo announced that it has recreated 60 percent of the garden using photos and virtual reality (VR) technology. The remainder has not been reproduced owing to a lack of solid historical records.

Yuanmingyuan, also known as Old Summer Palace, was first built in 1707 during the reign of Emperor Kangxi (1654-1722) of the Qing Dynasty (1644-1911). It was expanded and renovated in the following more than 200 years.

While years-long research has enabled Guo's team to derive a more profound understanding of the garden, they noted that some say Yuanmingyuan is a venue for patriotic education because it suffered continual war damage, while others say it bears testimony to the extravagant and lavish lifestyles of historical emperors. "However, these views both fail to tell the whole story," Guo said.

"We found through our studies that emperors lived and dealt with state affairs in the garden for much of its existence, which indicates that Yuanmingyuan was once the second political center of the Qing Dynasty after the Forbidden City," she explained.

Extensive research

Guo became fascinated with researching Yuanmingyuan in the late 1980s, when she led the designing of a park resembling Yuanmingyuan in Zhuhai, south China's Guangdong Province, which opened in 1997. The new park recreated less than half of the scenic spots in the imperial garden.

However, in Guo's mind, the new park was only a means of developing local tourism. It doesn't carry the cultural significance of Yuanmingyuan.

In 2000, she proposed the research of Yuanmingyuan. In order to carry out the project, Guo and her team have visited museums both in China and abroad to search for historical documents and design drawings of the garden. It took a lot of persuasion to get access to the precious materials, as most of them are so fragile that they are not available to the public.

She often led her students to conduct onsite investigations, looking for the ruins of artificial hills, ponds and bridges according to a map of the garden drawn in the 1930s.

The team studied the buildings and landscape arrangements in the garden according to historical maps and archeological discoveries. These studies enriched the researchers' knowledge of imperial garden construction in the Qing Dynasty.

The team found that the garden's appearance varied according to the governance mindset and aesthetic tastes of different emperors. For instance, during the reign of Emperor Qianlong (1711-99), who was very much concerned about agriculture, crops were grown in the garden to enable the emperor to gain some insight into the harvest situation across the country.

Going digital

Guo's team has published a number of academic papers on Yuanmingyuan based on extensive research. However, Guo felt this was far from enough to present the garden to the public.

Therefore, her team began to engage in the digital recreation of Yuanmingyuan in collaboration with Beijing Tsinghua Tongheng Urban Planning and Design Institute in 2009.

It took more than 10 stages to recreate a scenic spot, and every stage was completed based on historical materials.

"The color of every tree and plaque was determined through careful study, and baking technology was applied to reproduce the original light and shadow effects," Guo said.

In order to achieve accuracy, a 3-D model was made of each small component of architecture such as pillars, doors, windows and tiles.

Guo's team has developed multiple digital products using VR and augmented reality (AR) technologies. For instance, an AR application for iPad enables visitors to compare the current state of the ruins with their original appearances on the same screen.

The changes in architecture across a span of 300 years are also reflected in the digital reproduction.

The team will continue to push forward with its mixed reality project to further merge the virtual and real worlds to produce new replicated environments and visualizations where physical and digital objects coexist and interact in real time.

Controversy surrounding whether or not Yuanmingyuan should be rebuilt has continued for several decades. Guo opposes total reconstruction.

"Yuanmingyuan is a testimony to modern Chinese history and therefore the current state of its ruins should not be changed," she said, noting that it is also hard to find the same materials and tools used when building the original architecture, and the methods of construction cannot be replicated either. "Rebuilding the garden is irresponsible for future generations," Guo added.

Instead, she advocates recreating only 10 percent of the original buildings in Yuanmingyuan in order to provide more convenience for visitors and to complement existing landscapes. For instance, some parts may be rebuilt to provide shelter for visitors from the rain.

The digitalization of Yuanmingyuan is not alone in China's efforts to preserve cultural heritage with state-of-the-art technologies. Famous historical sites such as the Palace Museum in Beijing and the Buddhist grottoes in Dunhuang, Gansu Province, also have digital representations that preserve their cultural heritage and facilitate visitors' experience.

Copyedited by Chris Surtees

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