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Progressive Transmission of Appearance Preserving Octree-Textures

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.

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Progressive Transmission of Appearance Preserving Octree-Textures

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  1. Progressive Transmission ofAppearance Preserving Octree-Textures Web3D 2008 August 9, 2008 • Julien Lacoste • Camille Perin • Bruno Jobard • LIUPPA • University of Pau • France

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

  3. 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. 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. 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. 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 600 faces + Normal Map 69 000 faces 600 faces

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

  8. Talk Overview • APO Texture • Octree 1D encoding • 2D Texture Encoding • Network Architecture • Client/Server architecture • Appearance Data updates • Data TransmissionControl • Results

  9. APO Construction Octree 1D sorting • 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

  10. Conversion from 1D array to 2D texture Top texels: coarser levels Bottom texels: finer levels APO Construction APO 2D Encoding

  11. Viewer Architecture • Simple HTTP web server, only holds the data • No computation during transfer and rendering • The client viewer is a Java Applet using JOGL

  12. Viewer Architecture Client Viewer • 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

  13. Viewer Architecture Results After 30s After 2s After 10s • Demo: http://web.univ-pau.fr/~jlacoste/APOWebViewer/demoApplet.html

  14. Viewer Architecture Data Transfer Control • Finer details unnecessary → Data transfer stops • Computes screen-size projection of finer node • Stops when size is below one pixel

  15. 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

  16. THANKS !Questions Contact : julien.lacoste@univ-pau.fr http://web.univ-pau.fr/~jlacoste

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