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Progressive Transmission of Appearance Preserving Octree-Textures. Web3D 2008 August 9, 2008. Julien Lacoste. Camille Perin. Bruno Jobard. LIUPPA University of Pau France. A realistic image synthesis involves a great complexity for the object’s geometry. Motivations. - PowerPoint PPT Presentation
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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
3 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
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
4 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
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
5 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
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
6 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
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
7 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
Proposition
• Use the Appearance Preserving Octree-Texture (APO)– Octree-Texture encoding the normal map– Allows realtime rendering– Hierarchical representation → LOD Transmission
8 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
APO TextureOctree 1D encoding2D Texture Encoding
Network ArchitectureClient/Server architectureAppearance Data updatesData Transmission Control
Results
Talk Overview
9 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
• 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
10 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
Conversion from 1D array to 2D texture Top texels: coarser levels Bottom texels: finer levels
APO 2D Encoding
APO Construction
11 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
• 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
12 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
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
13 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
Results
Viewer Architecture
After 2s After 10s After 30s
• Demo:http://web.univ-pau.fr/~jlacoste/APOWebViewer/
demoApplet.html
14 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
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
15 / 16Julien Lacoste – Progressive Transmission of APO – Web 3D 2008
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 :julien.lacoste@univ-pau.fr
http://web.univ-pau.fr/~jlacoste
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