progressive transmission of appearance preserving octree-textures

Progressive Transmission ofAppearance Preserving Octree-

Textures

Camille Perin

Web3D 2008August 9, 2008

Julien Lacoste Bruno Jobard

LIUPPAUniversity of Pau

France

2 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008

• A realistic image synthesis involves a great complexity for the object’s geometry.

Motivations


On a distributed visualization system, the transmission of the full geometry takes too much time.

To avoid waiting time, use LOD representation of the geometry.

First a light low resolution model is transmitted

Higher resolution meshes are downloaded while interacting with low resolution object.

Motivations


Problem with LOD representation: The server holds several models Each version is fully transmitted: the

amount of data to transfer is increased Popping effect on the transition between

two levels To avoid these problems:

progressive representation of meshes

Motivations


Progressive Meshes (Hoppe, 96) Low Resolution Mesh + vertex split

operations No popping effect, smooth transition Download according to viewpoint

A major problem remains: Hard to render a complex geometry Distributed network: memory constraints

Motivations


69 000 faces69 000 faces 600 faces600 faces600 faces 600 faces

+ Normal Map+ Normal Map

For realtime rendering, the complexity can be encoded in a normal map, thus reducing the number of polygons.

How to tramsit efficiently only the appearance?

Motivations


Proposition

• Use the Appearance Preserving Octree-Texture (APO)– Octree-Texture encoding the normal map– Allows realtime rendering– Hierarchical representation → LOD Transmission


APO TextureOctree 1D encoding2D Texture Encoding

Network ArchitectureClient/Server architectureAppearance Data updatesData Transmission Control

Results

Talk Overview


• The octree is breadth first sorted in a 1D array– Each node has a pointer toward its first child– Root is at index 0, the coarser levels are the first

ones in the array• Internal nodes contain an averaged normal– Inner mip-mapping of the texture

Octree 1D sorting

APO Construction


Conversion from 1D array to 2D texture Top texels: coarser levels Bottom texels: finer levels

APO 2D Encoding

APO Construction


• Simple HTTP web server, only holds the data– No computation during transfer and rendering

• The client viewer is a Java Applet using JOGL

Viewer Architecture


Client downloads the simplified mesh (light) the APO while rendering

Each time the buffer is full / Each time step

Data sent to GPU to update APO (glTexSubImage)

Buffer cleared: client remains light in memory

Client Viewer

Viewer Architecture


Results

Viewer Architecture

After 2s After 10s After 30s

• Demo:http://web.univ-pau.fr/~jlacoste/APOWebViewer/

demoApplet.html


Finer details unnecessary → Data transfer stops

Data Transfer Control

Viewer Architecture

• Computes screen-size projection of finer node

• Stops when size is below one pixel


Progressive transmission of Appearance Nearly immediate interaction with low

resolution version of objects Details appear smoothly Manipulation of high detailed objects

No software installation Viewer is a browser applet

Data privacy Only low resolution meshes are transmitted

Conclusion

Julien Lacoste – Progressive Transmission of APO – Web 3D 2008 16 / 16

THANKS !Questions

Contact :[email protected]

http://web.univ-pau.fr/~jlacoste

progressive transmission of appearance preserving octree-textures

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