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A Novel Page-Based Data Structure for Interactive

Walkthroughs

Behzad SajadiYan Huang

Pablo Diaz-GutierrezSung-Eui Yoon

M. Gopi

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Outline

Page-Based Rendering Data Fetching Algorithm 2-Factor Data Layout Implementation and Results Summary Conclusion and Future Work

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Traditional Rendering Workflow

2

365

7

1

4

8

4

Page Based Rendering Workflow

2

3

1

4 65

78

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Page Format

Self contained information Less bytes for vertex indices Effective compression

# vertices# vertices # faces# faces List of vertices with attributes

List of vertices with attributes

Indexed triangle list with attributes

Indexed triangle list with attributes

Eliminating fragment accesses

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Traditional K-d tree Page based K-d tree

Storage

OScache

Processheap space

High data management

cost

No data management

cost

Low data management cost

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Major Steps of the Workflows

Traditional rendering workflow

Page based rendering workflow

SceneData

structureLayout

LayoutApproximated

sceneData

structure

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Advantages

Less space required for the data structure K-d tree on pages instead of triangles

Independence of the layout and data structure Any layout can be converted to the page

based format

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Outline

Page-Based Rendering Data Fetching Algorithm 2-Factor Data Layout Implementation and Results Summary Conclusion and Future Work

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Rendering Flow

K-d treestructure

RenderFetchdata

Page numbersafter VF Culling

Triangles

2

3

1

4

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Sorting the Page Numbers

Access pattern is based on storage

…

..

.

K-d tree without sorting

…

..

.

1,72,5 4,12 5,7 9,14 8,16

1, 2, 4, 5, 7, 8, 9, 12, 14, 16

K-d tree after sorting

1,72,5 4,12 5,7 9,14 8,16

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Rendering Flow

K-d treestructure

Sort pagenumbers

RenderFetchdata

Page numbersafter VF Culling

Triangles

1, 2, 4, 5

2

3

1

4

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Backface Culling

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Rendering Flow

K-d treestructure

Sort pagenumbers

RenderFetchdata

BackfaceCulling

Page numbersafter VF Culling

Triangles

1, 2, 4, 5

2

3

1

4

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Outline

Page-Based Rendering Data Fetching Algorithm 2-Factor Data Layout Implementation and Results Summary Conclusion and Future Work

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Related Works

Cache oblivious layout by Yoon et al. [2006]

Space filling curves Morton layout (Z-Order) Hilbert layout

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Graph Construction

Nodes: Group of triangles Edge weights: Distance between the

primitives of the nodes

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2.5

41.8

6.7

5

5.3

85

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Steps of the Method

Use GLA (Generalized Lloyd's Algorithm) to partition the primitives

Use [Diaz-Gutierrez and Gopi 2005] to get a 2-factor

Iterate in a hierarchical manner

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The Layout Hierarchy

Ordering using2-Factor Layouts

Partitioning usingGLA clustering

1 23 4 5 6 7

Final Layout: 2 1 6 7 4 5 3

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Advantages

Operates globally Scalable Amenable for multiple proximity

measures

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Outline

Page-Based Rendering Data Fetching Algorithm 2-Factor Data Layout Implementation and Results Summary Conclusion and Future Work

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The City Model

Floor planned using role playing city map generator 5.40

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The City Model (Contd.)

3D models of houses and trees were replaced

Cars were added in the streets

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The City Model (Contd.)

Specifications 110 million triangles 90 million vertices Spans 4528 MB Around 10,000 objects 115 million vertices in page format Spans 3814 MB in page format

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Texture Based Simplification

[Aliaga and Lastra 1997]

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Statistics

Frame rates Raster scan layout: 20 FPS Cache oblivious layout by Yoon et al.

[2006]: 27 fps 2-factor layout: 28 FPS

Rendering statistics (our layout) Page size: 4 KB Average disk-page per frame: 2365 Average triangle per frame: 240 K

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Statistics (Contd.)

Computation times Page format conversion: 15 min (Offline) K-d tree construction: 5 min (Offline) Billboard rendering: 20 hour (Offline) Program initialization: 20 sec

Consumed memory Billboards: 640 MB K-d tree: 96 MB (including bounding

boxes and normal cones)

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Outline

Page-Based Rendering Data Fetching Algorithm 2-Factor Data Layout Implementation and Results Summary Conclusion and Future Work

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Before Rendering (Offline) Steps

Given layoutConvert to thepage format

Construct thedisk-page hierarchy

2

3

1

4

Rendering (Online) Steps

K-d treestructure

Sort pagenumbers

RenderFetchdata

BackfaceCulling

Page numbersafter VF Culling

Triangles

1, 2, 4, 5

2

3

1

4

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Outline

Page-Based Rendering Data Fetching Algorithm 2-Factor Data Layout Implementation and Results Summary Conclusion and Future Work

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Conclusion

A simple data structure on the disk pages Simplicity High Performance Generality

A new cache oblivious layout

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Future Work

Analyzing the disk-page hierarchy on other data structures

Exploring other applications that can make use of this data structure

Including simplification techniques Adding a cache management system Analyzing the number cache hits and

misses

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Questions?