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Computer Graphics Group
Web-Based Presentations of Large Urban Scenes
Jiří ŽáraCzech Technical University
in Prague
Computer Graphics Group
http://www.cgg.cvut.cz
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Content
1. Requirements2. Models and Structures3. Data Acquisition4. Virtual Old Prague project5. Virtual Heart of Central Europe
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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What is the Virtual City?• A model of existing city
– Applications: cultural, tourist, GIS
• Fully artificial environment – cyber town(often with multi-user interaction)– Applications: games, social interaction
• Combination of real and virtual objects– Applications: architectural, artistic
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Richness of 3D Virtual Cities
• Additional info (text, images)• Hyperlinks• Interactivity (animations)• Virtual bus tour (animated viewpoint)• 2D map and 3D model synchronized• Search function• Automatic navigation (route planning)
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Web-based Virtual Cities
• Distributed application (client-server)
• Huge number of visitors (users)
• Providers’ needs (publicity)
• Users’ expectations (information source)
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Specific features of Virtual Cities• Large virtual space to be modeled [km]
• High number of real objects [100]
• Extensive use of textures/photos [1000]
photosDatabase
3D objects
plain images
GIS data2D maps
text
audio
video
InteractiveWeb
presentation
SERVER CLIENT
Internet
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Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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1. Requirements2. Models and Structures3. Data Acquisition4. Virtual Old Prague project5. Virtual Heart of Central Europe
Talk progress
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Part 2: Structuring Virtual Cities
• Panoramic VR
• Regular space partitioning
• General shapes
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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QuickTime VR
• Panoramic VR, Image based rendering• Based on QuickTime movie technology• Sensitive regions (hyperlinks)
+ high speed of rendering+ highly realistic look- large files (movies)- limited interactivity
Example
ExampleWeb-Based Presentations of Large Urban Scenes
CESCG 2004, Budmerice10
Computer Graphics Group
Grid layout - Alpha world
Multi-usercybercity
www.activeworlds.com
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Study case: Dublin
25 km2
From-area visibility
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Large Urban Areas
• Cells with a general shape• Progressive data transfer• Topology map (planar graph)• Visibility preprocessing
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Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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1. Requirements2. Models and Structures3. Data Acquisition4. Virtual Old Prague project5. Virtual Heart of Central Europe
Talk progress
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Part 3: Data acquisition
How to create a 3D model?• 3D reconstruction
(photos, laser)
• 3D modeling (3DS Max)
• Combined approaches (Canoma, PhotoModeler, Outline)
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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3D reconstruction (contd.)
+ High precision process– Not fully automated yet– Large unorganized meshes produced
Example
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Modeling toolsPhotoModeller
– mapping vertices and faces to photos
Canoma– mapping 3D primitives (box, pyramid) to
photos
Outline– mapping 2D objects (window, door, roof)
to a single photo of a façade
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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PhotoModeler
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Canoma
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Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Canoma example 1
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Canoma example 2
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Using aerial photos
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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“Outline” tool
• Developed for the Virtual Old Prague project
• Produces composite texture files• Generates “Urban LOD” for VRML
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Urban LOD
110,5 kB
213,7 kB
2311,5 kB
9116,2 kB
speed of data transfer
renderingspeed
quality of rendering
X
X
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Outline tool
Example
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Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Texture acquisitionPhotographic conditions:
Dark (against the sun)
Obstacles
“The best weather isa bad weather”
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Perspective distortionhorizontal
Texture acquisition (contd.)
vertical
Objectsappearingon differentpositions
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Texture acquisition (contd.)
Cleaning processWeb-Based Presentations of Large Urban Scenes
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1. Requirements2. Models and Structures3. Data Acquisition4. Virtual Old Prague project5. Virtual Heart of Central Europe
Talk progress
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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4. Virtual Old Prague
• Based on VRML• Data loaded/unloaded on the fly
• Visibility preprocessing (PVS)
• Tuned for web presentation(Urban LOD)
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Structuring the citysector
gatefacade
3D object
Granularity
Scaleability
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Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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ExampleWeb-Based Presentations of Large Urban Scenes
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Computer Graphics Group
0100200300400500600700800900
1000
Valds
tejns
ke
Snem
ovni
Malo
stran
ske
Mos
teck
a
cumulative
running
Data transfer[kB]
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Statistics
• About 270 houses• 20 streets• 5 squares• 80 cells• 40 solitaires (3D objects)• Amount of data per LOD:
3 MB / 970 kB / 300 kB
0
500
1000
1500
2000
2500
3000
LOD 3 LOD 2 LOD 1
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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1. Requirements2. Models and Structures3. Data Acquisition4. Virtual Old Prague project5. Virtual Heart of Central Europe
Talk progress
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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5. Virtual Heart of Central Europe
• Culture 2000 programme (EU)• Web-based visualization of selected
historical and cultural objects fromBratislava, Graz, Maribor, and Prague
• Integration of various technologies: images, video, QTVR, VRML, sound
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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VHCE project - examples
1. Single objects
2. Object & environment (imposters)
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Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Optimization Advices
• Small textures (resolution, not file size)
• DEF once, USE many (objects, urls)
• Remove normal vectors, set creaseAngle
• Use primitives & low poly meshes
• Limit light sources (max. 8)
• Avoid collision detection Example
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Conclusion
Main issues to be solved?
1. 3D reconstruction2. Web visualization3. User interface
} Specialized
– Common
Web-Based Presentations of Large Urban ScenesCESCG 2004, Budmerice
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Conclusion contd.Virtual cities require synchronized
effort of experts from various fields:
• Computer vision• Computer graphics• Databases, GIS• Networking • Architecture
• History• Gaming• Education• Business• … any other?
Methods MotivationsWeb-Based Presentations of Large Urban Scenes
CESCG 2004, Budmerice40
Computer Graphics Group
www.cgg.cvut.cz/vsp/
www.vhce.info/
Thank you for your attention
Jiří Žára
Presentations online