Try to imagine a night scene in an ancient Chinese capital 900 years ago. That was the tricky part in making an animated version of the Qing dynasty painting Riverside Scene at Qingming Festival, a star in the China pavilion at Shanghai's World Expo, its creator said yesterday. The animated exhibit is a moving version of a renowned work painted by Zhang Zeduan 900 years ago. A duplicate will be displayed at the AsiaWorld-Expo in Hong Kong from November 9 to 29. Crystal Digital Technology, the firm that made the animated painting, was replicating it in Hong Kong, exhibition business department director Yu Zheng said. The version shown here will be almost identical to the one at the World Expo. The painting shows life in Kaifeng, formerly known as Bianjing, capital of the Northern Song dynasty. It features computer animation projected on a screen about 120 metres long and six metres high, 30 times as big as the ancient scroll. One striking difference is that the painting features the city during the day, while the animation shows a transition from day to night. 'How did Kaifeng look like during nighttime? We don't have many historical references for that,' Yu said. 'Nevertheless, we incorporated what people did at night such as drinking and eating at stalls ... and we asked experts what lanterns looked like in the Northern Song dynasty.' Many types of lanterns were shown in the animation, including some placed in rivers and others held by residents, he said. The company also drew reference from an unlikely source on how ancient Chinese cities were depicted at night: video games. Various activities along the river are shown by moving figures - people stroll, visit markets and row boats. 'There are more than 1,000 moving characters. We assigned them a name, a face, motions and a route they move along,' Yu said. The display in Hong Kong will take place when the China Pavilion is closed. After the World Expo ends on October 31, the pavilion will close for a month and reopen in December. The production cost for the exhibition is HK$18 million. Visitors can view the work for an hour for HK$10. The curator of the Science Museum, Karen Sit Man, said: 'Visitors to the Shanghai World Expo may have to rush in order to visit various pavilions, whereas in Hong Kong, they can focus on a single exhibit.'