Method for compressing/decompressing a three-dimensional mesh

An encoder (100) for three-dimensional meshes, characterized in that it is configured:

• to receive and store:
• connectivity data T,
• geometry data G,
• references of user-selected “control dots” Cs, which dots make it possible to generate an approximate version of the original mesh M, where a subset represents 1% of the vertices of the mesh,
• a single rate type of connectivity encoder (11), i.e. without scalability, designed for lossless encoding of the connectivity data T into compressed connectivity data Tc,
• a quantization module (12) designed to process the geometry data G in order to reduce the volume of information to be transmitted for each vertex,
• a control dot selection module (13) utilizing:
• the quantized geometry data GQ;
• the compressed connectivity data Tc;
• and the user control dot data Cs to provide the selected control dots C;
• a protruding edge detection module (16), designed to use the compressed connectivity data Tc and the geometry data;
• a binarization module (17) to produce the compressed indexes of the protruding edges SC and the compressed indexes and positions of the control dots CC;
• a mesh approximation module (21) designed to integrate the selected control dot data C and the compressed connectivity data Tc;
• this mesh approximation module (21) generates an approximate mesh M*;
• a mesh decimation module (22), designed to provide a progressive mesh PM(M*) based on the approximate mesh M* and the quantized geometry data GQ;
• an prediction module (23) for approximation errors ev designed to use the data output from the mesh decimation module (22)
• from which compressed error prediction data evc are output, after compression by an arithmetical encoder;
• and to transmit:
• compressed connectivity data Tc;
• compressed indexes of protruding edges SC;
• compressed indexes and positions of the control dots CC;
• and compressed error prediction data evc.

A decoder (200) for three-dimensional meshes, characterized in that it is configured:

• to receive and store:
• compressed connectivity data Tc;
• compressed indexes of protruding edges SC;
• compressed indexes and positions of the control dots CC;
• and compressed error prediction data evc;
• a single-rate connectivity decoder (31) designed to provide reconstituted connectivity data T′ from the compressed connectivity data Tc;
• an inverse binarization module (37) designed to provide indexes of the protruding edges S′, indexes and positions of the control dots C′ and compression error prediction data ev′;
• a mesh approximation module (41) designed to combine reconstituted connectivity data T′, indexes of protruding edges S and indexes and positions of the control dots C′;
• a mesh decimation module (42) designed to use the approximate mesh M* to obtain a progressive mesh PM(M*),
• an inverse approximation error prediction module (43) designed to combine the progressive mesh data PM(M*) with the compression error prediction data ev′;
• an inverse quantization module (32) able to provide reconstituted geometry data G′ based on the results of the inverse approximation error prediction module.