interactive walkthrough in virtual cities and its applications in urban design

University of Alexandria

Institute of Graduate Studies and Research

Department of Information Technology

Interactive Walkthrough in Virtual Cities

and its Applications in Urban Design

Master's Thesis Defense Presentation2009 November 92009 November 9

Khaled Mohamed Ahmed Abd El Gawad

Examination Committee:

Prof.Dr. Ayman El-Dessouky Ibrahim

Prof. Dr. Shawkat Kamal Guirguis

Dr. Walaa Mohamed Sheta

Supervisors:


Dr. Sahar El-sayed Bayoumi

Outline

� Motivation

� Objective

� Contribution

� literature review

5/28/2010 2

� Methodology

� Experiments and Results

� Future Work

Motivation

� 3D Virtual City Applications diversity.

� Applications in urban design.

� Egyptian non-structured cities.

5/28/2010 3

� Increasing size of 3D datasets makes them impossible

to display in real time with classical approaches.

Objective

� Improve visibility culling performance in non-structured

virtual city

�Study performance for the developed visibility

algorithm

5/28/2010 4

Main Contribution

� Developing potentially visible set (PVS) algorithm on

non-structured virtual city

� Providing a new technique to calculate offline 2d

visibility for virtual city based on user predefined

budget (accuracy, time and storage media size)

5/28/2010 5

budget (accuracy, time and storage media size)

� (PVS) algorithm over perform partitioning algorithm on

non-structured virtual city

Literature Review

� Virtual Bath (CASA group)

�Visibility culling (back-face, view-frustum)

�Occlusion culling algorithms

5/28/2010 6

View frustum

eye

View frustum

back

face

Occlusion

Literature Review cont.

�Potentially visible set Algorithm

� Run-time / pre-process calculating

� Indoor Scenes Cell and Portal

� Outdoor Scenes

5/28/2010 7

� Outdoor Scenes

Methodology

1. Building a virtual walkthrough prototype system for

both acceleration algorithms (PVS - partitioning)

2. Applying both algorithms on two virtual cities with

different urban patterns (non structured – well

planned)

5/28/2010 8

planned)

3. Measuring performance

4. Analyzing results and outcomes

Prototype Implementation

� System Architecture Overview

PVS

module

Partitioning

module

Make Partitions

5/28/2010 9

Make Partitions

Prototype Implementation cont.


PVS

module

Partitioning

module

Make Partitions

5/28/2010 10

Make Partitions

� 2D View Cell Analyzer

� View Cell Manipulator

Prototype Implementation: PVS Module

5/28/2010 11


� 2D View Cell Analyzer� Non-structured city.

5/28/2010 12


� 2D View Cell Analyzer� Well-planned city.

5/28/2010 13


� View Cell Manipulator


5/28/2010 14


� PVS Calculating


5/28/2010 15


5/28/2010 16


� PVS Calculating


5/28/2010 17



PVS

module

Partitioning

module

Make Partitions

5/28/2010 18

Make Partitions

� Walkthrough Generator 1


5/28/2010 19



5/28/2010 20

� Walkthrough Generator 1� Routing Map


5/28/2010 21

When the user

enters a view cell



PVS

module

Partitioning

module

Make Partitions

5/28/2010 22

Make Partitions

� Partitioning Tool

� Find Polygon/Partition Center

Prototype Implementation: Partitioning

Make Partitions

5/28/2010 23


� Find Polygon/Partition Center


Make Partitions

5/28/2010 24


Make Partitions


� Create Partitions

5/28/2010 25


Make Partitions

5/28/2010 26


Make Partitions

5/28/2010 27



PVS

module

Partitioning

module

Make Partitions

5/28/2010 28

Make Partitions



5/28/2010 29



PVS

module

Partitioning

module

Make Partitions

5/28/2010 30

Make Partitions

Outline so far:

� Motivation

� Objective

� Contribution

� literature review

5/28/2010 31

� Methodology

� Experiments and Results

� Future Work

Experiments and Results

� Dataset description

5/28/2010 32

Well planned : Al Ahram Garden

277 building

Non structured: Wasat El Delta

277 building

� Navigation Patterns

Experiments and Results cont.

5/28/2010 33

Random Walk

(RW)

Spiral Pattern

(SP)

Changed Circular Pattern

(CCP)

� Experiment #1

Sub Experiment 1-1 1-2 1-3 1-4 1-5

The view cell size against the number of loaded objects in the

non-structured urban pattern city when applying the PVS

algorithm


5/28/2010 34

View Cell No. 2 4 8 16 32

View cell size 800 X 300 400 X 300 400 X 150 200 X 150 200 X 75

1-1 1-2 1-3 1-4 1-5

132.75134

182 201

161

150

200

250

Nu

mb

er

Of

Loa

de

d O

bje

cts

Non-Structured City – PVS Algorithm

Experiments and Results: Experiment #1

5/28/2010 35

112

132.75

116.875

81.4375

55.96875

9078

58

2626

112

0

50

100

800 X 300 400 X 300 400 X 150 200 X 150 200 X 75

Average No Of Objects

Min No. Of Objects

Max No. Of Objects

View Cell Size

Nu

mb

er

Of

Loa

de

d

� Experiment #2

The view cell size against the number of loaded objects in the

well planned urban pattern city when applying the PVS

algorithm


Sub Experiment 2-1 2-2 2-3 2-4 2-5

5/28/2010 36

2-1 2-2 2-3 2-4 2-5



203

172.25160

246 246

219

206

162

200

250

300

Nu

mb

er

Of

Loa

de

d O

bje

cts

Well Planned City – PVS Algorithm


5/28/2010 37

150.75

124.5625

98.3125

160

121

83

42

46

162

0

50

100

150

800 X 350 400 X 350 400 X 175 200 X 175 200 X 75

Average No. Of Objects

Min No. Of Objects

Max No. Of Objects

View Cell Size

Nu

mb

er

Of

Loa

de

d

250

300

No

. o

f lo

ad

ed

Ob

ject

s

Well planned Max No of objects

Non structured Max No of objects


� Experiments #1 and #2 conclusions

5/28/2010 38

0

50

100

150

200

280k 240k 120K 140k 70k 60K 35k 30K 15k

No

. o

f lo

ad

ed

Ob

ject

s

View Cell Size

200

250

No

. o

f lo

ad

ed

Ob

ject

s

Well planned Avg no of objects

Non structured Avg no of objects



5/28/2010 39

0

50

100

150

200

280k 240k 120K 140k 70k 60K 35k 30K 15k

No

. o

f lo

ad

ed

Ob

ject

s

View Cell Size

140

160

180

No

. o

f Lo

ad

ed

Ob

ject

s

Well planned Min No of objects

Non structured Min No of objects



5/28/2010 40

0

20

40

60

80

100

120

140

280k 240k 120K 140k 70k 60K 35k 30K 15k

No

. o

f Lo

ad

ed

Ob

ject

s

View Cell Size

� Experiment #3

The view cell size against the frame rate in the well planned

urban pattern city when applying the PVS algorithm.


Sub Experiment 2-1 2-2 2-3 2-4 2-5

5/28/2010 41



29.4907818129.96435728

30.13162235

28.68523507

29.84108181

24.93212933

22.7490917522.97267238

23.20343061

24

26

28

30F

ram

e R

ate


5/28/2010 42

19.1571897719.63045629

18.46098643

19.20655074

16.91969015

21.15675006

22.7490917522.97267238

23.20343061

16

18

20

22

800 X 350 400 X 350 400 X 175 200 X 175 200 X 75

RW

CCP

SP

View Cell Size

Fra

me

Ra

te

Well planned - PVS

� Experiment #4

The view cell size against the frame rate in non structured

urban pattern city when applying the PVS algorithm


Sub Experiment 1-1 1-2 1-3 1-4 1-5

5/28/2010 43



28.0897360727.52872754 27.50527764

22.78121455

29.24600028

29.7310093

28.76899778

30.99649029

23

28

33F

ram

e R

ate


5/28/2010 44

16.73338993

14.44401665

17.54001673

19.89686771 19.8479581620.64370651

20.61034316

22.78121455

13

18

23

800X300 400X300 400X150 200X150 200X75

RW

CCP

SP

View Cell Size

Fra

me

Ra

te

Non structured- PVS

� Experiment #5

The partition size against the frame rate in well planned city

when applying the partitioning algorithm


Sub Exp. 5-1 5-2 5-3 5-4 5-5 5-6

5/28/2010 45

Partitions No. 2 4 8 16 32 64

Partitions size 400X610 400X305 200X305 200X155 100X155 100X77

16.04837325

14.63680569

15.690212716.33234097

20.197540420.67608491

15.10331206

17.66874392

15

20

25F

ram

e R

ate


5/28/2010 46

6.6358462647.16564891

7.9255450758.594371213 9.045524881 9.250304366

11.79780791

10.05555103

10.44367175

11.45429424

0

5

10

2 par 400X610 4 par 400X305 8 par 200X305 16 par 200X155 32 par 100X155 64 par 100X77

RW

CCP

SP

Partition Size

Fra

me

Ra

te

Well planned - Partitioning

� Experiment #6

The partition size and the frame rate in non structured urban

pattern city when applying the partitioning algorithm


Sub Exp. 6-1 6-2 6-3 6-4 6-5 6-6

5/28/2010 47

Partitions No. 2 4 8 16 32 64

Partitions size 375X500 375X250 190X250 190X145 100X145 100X75

22.69119622

24.62832275

22.73839676

27.53329429

30.6624535

33.0433291633.47852866

27

32

Fra

me

Ra

te


5/28/2010 48

11.43958488

9.332535195

12.97570919

16.03335947

22.69119622

16.3419815.31591728

18.54151373

20.94712329

22.27447554

23.2409737721.71500904

22.73839676

7

12

17

22

2 par 375X500 4 par 375X250 8 par 190X250 16 par 190X145 32 par 100X145 64 par 100X75

RW

CCP

SP

Partition Size

Fra

me

Ra

te

Non structured - Partitioning

City

TypePath type

Partitioning Algorithm Potential Visible Set (PVS)

2 par 4 par 8 par 16 par 32 par 64 par 2 Sens 4 Sens 8 Sens 16 Sens 32 Sens

structured RW 11.43958488 9.33254 12.9757 16.0334 22.6912 24.6283 16.7334 14.444 17.54 19.8969 19.84796


� Results Matrix

5/28/2010 49

Non

structured

CCP 16.34198 15.3159 18.5415 20.9471 22.2745 23.241 20.6437 20.6103 28.0897 27.5287 27.50528

SP 21.71500904 22.7384 27.5333 30.6625 33.0433 33.4785 22.7812 29.246 29.731 28.769 30.99649

2 par 4 par 8 par 16 par 32 par 64 par 2 Sens 4 Sens 8 Sens 16 Sens 32 Sens

Well planned

RW 6.635846264 7.16565 7.92555 8.59437 9.04552 9.2503 19.1572 19.6305 18.461 19.2066 16.91969

CCP 16.04837325 14.6368 15.6902 16.3323 20.1975 20.6761 29.4908 29.9644 30.1316 28.6852 29.84108

SP 11.79780791 10.0556 10.4437 15.1033 11.4543 17.6687 24.9321 21.1568 22.7491 22.9727 23.20343

Conclusion and Discussion� The highest number of occluded objects and frame

rate can be obtained when applying PVS algorithm on

non structure city

� PVS algorithm over perform partitioning algorithm in

non structured city

5/28/2010 50

Future Work� Providing a 3d visibility technique based on user

predefined budget

� Studying performance for the developed algorithm

compared to other algorithms

� Enhance the developed algorithm to be used in virtual

5/28/2010 51

� Enhance the developed algorithm to be used in virtual

cities with dynamic objects

Thank You

Discussion

5/28/2010 52

Discussion

University of Alexandria

Institute of Graduate Studies and Research

Department of Information Technology

Interactive Walkthrough in Virtual Cities

and its Applications in Urban Design

Master's Thesis Defense Presentation2009 November 92009 November 9

Khaled Mohamed Ahmed Abd El Gawad

Examination Committee:

Prof.Dr. Ayman El-Dessouky Ibrahim

Prof. Dr. Shawkat Kamal Guirguis


Prototype Implementation

� Software Used

Modeling Phase

AutoCAD 3DS MAX Photoshop CS3

5/28/2010 54

AutoCAD 3DS MAX

Simulation Phase

Flash CS4

AS 3

VRML97 Vrmlpad Cortona player Scripting

Photoshop CS3

For further information

5/28/2010 55

For further information

see the following slides


� Interactive Walkthrough (well planned) PVS

5/28/2010 56


� Interactive Walkthrough (non structured) PVS

5/28/2010 57


� Interactive Walkthrough (Log file structure) PVS

5/28/2010 58

Tracking Loaded

View Cells

� Experiments environment

Operating System Windows XP Professional (5.1,

Build 2600) Service Pack 2

(2600.xpsp_sp2_gdr.070227-


5/28/2010 59

(2600.xpsp_sp2_gdr.070227-

2254)

Processor Intel(R) Celeron(R) CPU

2.53GHz

Memory 478MB RAM

Display Devices SiS 661FX

Display Memory 32.0 MB

� Partitioning Tool� Non-structured city.


Make Partitions

5/28/2010 60

� Partitioning Tool� Well-planned city.


Make Partitions

5/28/2010 61

Conclusion and Discussion

15

20

25

Fra

me

Ra

teNon structured city (RW)

PVS

5/28/2010 62

0

5

10

280K 144K 70K 35K 15K

Fra

me

Ra

te

Partitioning


PVS

20

25

30

Fra

me

Ra

teNon structured city (CCP)

5/28/2010 63

Partitioning

0

5

10

15

280K 144K 70K 35K 15K

Fra

me

Ra

te


Partitioning

PVS

20

25

30

35

Fra

me

Ra

teNon structured City (SP)

5/28/2010 64

Partitioning

0

5

10

15

20

280K 144K 70K 35K 15K

Fra

me

Ra

te

interactive walkthrough in virtual cities and its applications in urban design

Education

d view cell analyzer

partitioning algorithm

view cell size

acceleration algorithms

visible set pvs algorithm

view frustum eye view

viewfrustum occlusion

virtual cities