A Case Study of Virtual Museum: Reconstruction and Restoration of Dunhuang Caves in China Jiaoying Shi State Key Lab of CAD&CG College of Computer Science and Engineering Zhejiang University

Contents 1.Introduction of Dunhuang Mogao Caves 2.Reconstruction of Dunhuang Mogao Caves 3.Restoration of the Murals in Dunhuang Mogao Caves

1. Introduction of Dunhuang Mogao Caves 1)It’s located in North-West desert area of China 2)Start excavating in Jin Dynasty(336 A.D), 1600 years old.

3)There still exist 492 intact caves, more than 2400 painted sculptures, over square meter murals and wood architectures of Tang and Song Dynasty murals painted sculptures architectures

4)Named as World History and Culture Heritage by UNESCO in 1987 UNITED NATIONS EDUCATIONAL SCIENTIFIC AND CULTURAL ORGANIZATION CONVENTION CONCERNING THE PROTECTION OF THE WORLD CULTURAL AND NATURAL HERITAGE The World Heritage Committee Has inscribed The Mogao Caves On the world Heritage list Inscription on this List confirms the exceptional And universal value of a cultural or Natural site which requires protection for the benefit Of all humanity

5)The perennial invasion of sand blown by the wind has also done great damage to the treasury, thus putting it in severe danger. 6)In order to protect the Mogao Caves furthermore, today a severe measure of limiting the visitors number is taken by the local administrator. 7)So it is very urgent to build a virtual Museum of Dunhuang Mogao Caves to disseminate this World Cultural Heritage broadly.

2. Reconstruction of Dunhuang Mogao Caves Surveying the caves Modeling the caves

Digitizing the murals ◆ photographing bracket ◆ Demo of Shooting The criterion: well-proportioned lighting, parallel moving and partial overlaps

Mapping the murals onto the model Mapping

Mosaicing Images

Digitization of three-dimensional culture relics Acquiring high-precision 3D models by 3D scanner Acquiring high-precision 3D models by 3D scanner The model acquired by 3D scan The model acquired by 3D scan

Digitization and modeling of outdoor scene 1 2 Take photos of out-door scene in a fixed point Adjusting and mosaicing

Demo1: The navigation of Dunhuang Mogao Caves

Demo2: The navigation of Outdoor Scene of Dunhuang Mogao Caves

3. Restoration of the Murals of Dunhuang Mogao Caves The murals and sculptures in Dunhuang Mogao Caves have experienced color changes and impairment over 1600 years. Introducing 3 techniques for virtual restoration of the mural color of Dunhuang Mogao Caves.

Virtual Color Restoration Reasoning Based on Scientific Rules Analogical Thinking Model Reasoning Based on experience knowledge

1)Reasoning Based on Scientific Rules Experience Knowledge Experience Knowledge Chemical Color Changing Rule Chemical Color Changing Rule Physical Color Changing Rule Physical Color Changing Rule Compute r Color Changing Model in Computer

Chemical Color Changing Rule According to the chemical knowledge of Dunhuang researchers, we got the Chemical Color Changing Rule. Changing gradually Red Lead Oxide (PbO 2 ) + Oxygen(O 2 ) Pb 3 O 4

Physical Color Changing Rule Over some time t, the color gradually changes or fades by covered dust. It is essential a color mixing process of the mural’s color and dust’s color Let mural color C b （ R b ， G b ， B b ）, dust color C f （ R f ， G f ， B f ）, the transparence of C f be X%, then the mixing color is: RGB(160,168,171) + RGB(119,71,31) RGB(150,144,136) 25% Transparence 25% Transparence

2)Analogous Thinking Model The same dynasty and cave Multi-layer muralMulti-layer mural This is the inner layerThis is the inner layer not been oxygenated after outer layer fell off The unoxygenated color element provide the source knowledge for analogous reasoning

3)Reasoning Based on Experience Knowledge of the Dunhuang Artists and Researchers The set of Dunhuang typical color of the Tang Dynasty: Red Yellow Blue Green Brown Gray White Golden

Color Region Obtaining Edge Destination Color Layering Based on the set of typical color of Dunhuang Reasoning Based on Experience Knowledge of the Dunhuang Artists and Researchers

Refer the color well-protected mural image to restore Source Image Anology Reference Destination Image Dunhuang Mural Color Virtual Restoration—Example of Color Faded Restoration

According to the Chemical Color Gradually Changing Rule to restore Source Image Destination Image Chemical Color Gradually Changing Rule

Dunhuang Mural Color Virtual Restoration—Example of Color Faded Restoration Integrating Color Faded Restoration and Color Changed and Color ChangedRestoration Source Image Destination Image

Dunhuang Mural Color Virtual Restoration—Example of Color Faded Restoration Using Created Pattern to restore faded region Source Image Created Pattern Destination Image

Demo3: Dunhuang Mural Color Changing Process

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