Progressive Transmission of Appearance Preserving Octree-Textures Camille Perin Web3D 2008 August 9, 2008 Julien LacosteBruno Jobard LIUPPA University of Pau France
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 A realistic image synthesis involves a great complexity for the object’s geometry. Motivations
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 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
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 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
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 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
Julien Lacoste – Progressive Transmission of APO – Web 3D / faces 600 faces + 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
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 Proposition Use the Appearance Preserving Octree-Texture (APO) – Octree-Texture encoding the normal map – Allows realtime rendering – Hierarchical representation → LOD Transmission
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 APO Texture Octree 1D encoding 2D Texture Encoding Network Architecture Client/Server architecture Appearance Data updates Data Transmission Control Results Talk Overview
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 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
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 Conversion from 1D array to 2D texture Top texels: coarser levels Bottom texels: finer levels APO 2D Encoding APO Construction
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 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
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 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
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 Results Viewer Architecture After 2sAfter 10s After 30s Demo:
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 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
Julien Lacoste – Progressive Transmission of APO – Web 3D / 16 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 / 16 THANKS ! Questions Contact :