A Case Study of Virtual Museum: Reconstruction and Restoration of Dunhuang Caves i

n China

Jiaoying ShiState Key Lab of CAD&CG

College of Computer Science and EngineeringZhejiang University

jyshi@cad.zju.edu.cn2003.8

Contents

1. Introduction of Dunhuang Mogao Caves2. Reconstruction of Dunhuang Mogao Cave

s3. Restoration of the Murals in Dunhuang Mo

gao Caves

1. Introduction of Dunhuang Mogao Caves1) 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 45000 square meter murals and wood architectures of Tang and Song Dynasty

muralsmurals

painted sculpturespainted sculptures

architecturesarchitectures

4) Named as World History and Culture Heritage by UNESCO in 1987

UNITED NATIONS EDUCATIONAL UNITED NATIONS EDUCATIONAL SCIENTIFIC AND CULTURAL ORGSCIENTIFIC AND CULTURAL ORG

ANIZATIONANIZATIONCONVENTION CONCERNING THE CONVENTION CONCERNING THE

PROTECTION OF PROTECTION OF THE WORLD CULTURAL AND NATTHE WORLD CULTURAL AND NAT

URAL HERITAGEURAL HERITAGEThe World Heritage CommitteeThe World Heritage Committee

Has inscribedHas inscribedThe Mogao CavesThe Mogao Caves

On the world Heritage listOn the world Heritage listInscription on this List confirms the eInscription on this List confirms the e

xceptionalxceptionalAnd universal value of a cultural orAnd universal value of a cultural or

Natural site which requires protection Natural site which requires protection for the benefitfor the benefitOf all humanityOf 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

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The criterion: well-proportioned lighting, parallel moving The criterion: well-proportioned lighting, parallel moving and partial overlapsand partial overlaps

• Mapping the murals onto the model

MappingMapping

Mosaicing ImagesMosaicing Images

• Digitization of three-dimensional culture relics

• Acquiring Acquiring high-high-precision precision 3D models 3D models by 3D by 3D scannerscanner

• The model acquired by 3D scanThe model acquired by 3D scan

• Digitization and modeling of outdoor scene

1

2

Take photos of out-door scene in a fixed Take photos of out-door scene in a fixed pointpoint

Adjusting and Adjusting and mosaicingmosaicing

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 C

aves 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 Virtual Color RestorationRestoration

Reasoning Reasoning Based on Based on Scientific Scientific

RulesRules

AnalogicaAnalogical Thinking l Thinking

ModelModel

Reasoning Reasoning Based on Based on

experience experience knowledgeknowledge

1) Reasoning Based on Scientific Rules

ExperiencExperience e

KnowledgKnowledge e

Chemical Chemical Color Color

Changing Changing RuleRule

Physical Physical Color Color

Changing Changing RuleRule

ComputComputerer

Color Changing ModelColor Changing Modelin Computerin Computer

Chemical Color Changing RuleAccording to the chemical knowledge of Dunhuang researAccording to the chemical knowledge of Dunhuang researchers, we got the Chemical Color Changing Rule.chers, we got the Chemical Color Changing Rule.

Changing graduallyChanging gradually

Red Lead OxideRed Lead Oxide (PbO (PbO22 ) + Oxygen(O ) + Oxygen(O2 2 ) Pb) Pb33OO44

Physical Color Changing RuleOver some time t, the color gradually Over some time t, the color gradually changes or fades by covered dust. changes or fades by covered dust. It is essential a color mixing process of the It is essential a color mixing process of the mural’s color and dust’s colormural’s color and dust’s color

Let mural color Let mural color CCbb （（ RRbb ，， GGbb ，， BBbb ）） , dust color , dust color CCff （（ RRff ，， GGff ，， BBff ）） , the transparence of , the transparence of CCff be be XX%, then the mixing color is:%, then the mixing color is:

%)%)1(%,%)1(

%,%)1((%),,(

XBXBXGXG

XRXRXCCA

bfbf

bffb

RGB(160,168,171) + RGB(119,71,31) RGB(150,144,136)RGB(160,168,171) + RGB(119,71,31) RGB(150,144,136) 25% Transparence25% Transparence

2) Analogous Thinking Model

The same dynastyThe same dynastyand caveand cave

•Multi-layer Multi-layer muralmural•This is the inner layer This is the inner layer not been oxygenatednot been oxygenatedafter outer layer fell offafter outer layer fell off

The unoxygenated color elementThe unoxygenated color elementprovide the source knowledge for provide the source knowledge for analogous reasoninganalogous reasoning

3) Reasoning Based on Experience Knowledge of the Dunhuang Artists and Researchers

The set of Dunhuang typical color of the Tang Dynasty:The set of Dunhuang typical color of the Tang Dynasty:

RedRed

YellowYellow

BlueBlue

GreenGreen

BrownBrown

GrayGray

WhiteWhite

GoldenGolden

Color Region ObtainingColor Region Obtaining

Edge DestinationEdge Destination

Color LayeringColor Layering

Based on the set of typicBased on the set of typical color of Dunhuangal color of Dunhuang

Reasoning Based on Experience Knowledge of the Dunhuang Artists and Researchers

Refer the Refer the color well-color well-protected protected mural image mural image to restoreto restore

Source ImageSource Image

Anology ReferenceAnology Reference

Destination Destination ImageImage

Dunhuang Mural Color Virtual Restoration—Example of Color Faded Restoration

Dunhuang Mural Color Virtual Restoration—Example of Color Faded Restoration

According to the According to the Chemical Color Chemical Color Gradually Gradually Changing Rule to Changing Rule to restorerestore

Source ImageSource Image Destination Destination ImageImage

Chemical Color Gradually Changing RuleChemical Color Gradually Changing Rule

Dunhuang Mural Color Virtual Restoration—Example of Color Faded Restoration

Integrating Color Integrating Color Faded Faded RestorationRestoration and Color and Color Changed Changed RestorationRestoration

Source ImageSource Image Destination Destination ImageImage

Dunhuang Mural Color Virtual Restoration—Example of Color Faded Restoration

Using Created Using Created Pattern to Pattern to restore faded restore faded regionregion

Source ImageSource Image

Created PatternCreated Pattern

Destination ImageDestination Image

Demo3: Dunhuang Mural Color Changing Process

Thanks!