Thomson Licensing

Kang Ying Cai

Zhi Chen

Qu Qing Chen

Jun Teng

Yu Jin

Wei Wei Li

3D mesh models are represented by three types of data: connectivity data, geometry data and property data. The surface of a 3D object is a triangle mesh. 3D meshes contain huge amounts of data that need to be compressed efficiently. Additionally to the common world coordinate system for the complete model and local coordinate system for a single triangle, an individual component coordinate system for each connected component is used. The component coordinate system is used to normalize the orientation of the respective component for quantization and de-quantization. This improves the accuracy of encoded 3D mesh models after quantization/de-quantization, particularly if a 3D mesh model comprises one or more distinct components.

Method for encoding/decoding a 3D mesh model that comprises one or more components

A method for encoding vertex orientations, also known as normal components, of a 3D mesh model comprises a first clustering of the normal components, determining for each of the first clusters a sphere sector to which most of its elements belong, mapping normal components to a predefined sector, re-clustering the normal components in the predefined sector into second clusters, determining predictors for the second clusters and encoding a normal component by its residual, a reference to its predictor and data indicating which of said mirror mapping operations were performed. A sphere sector is obtained by dividing a sphere into m equal spherical segments and dividing each of said spherical segments into n equal sectors. The first clustering for the sector mapping and the second clustering for predictive coding result in an improved compression ratio.

Method for encoding normals of a 3D mesh model, method for decoding normals of a 3D mesh model, encoder and decoder

For most large 3D engineering models, the instance positions of repeating instances of connected components show significant multiple spatial aggregation. The invention uses several KD-trees, each for one cluster of points which are spatially aggregated. The multiple KD-trees generate a relatively short data stream, and thus improve the total compression ratio. A method for encoding points of a 3D mesh model comprises steps of determining that the mesh model comprises repeating instances of a connected component, and determining for each repeating instance at least one reference point, clustering the reference points of the repeating instances into one or more clusters, and encoding the clustered reference points using KD-tree coding, wherein for each cluster a separate KD-tree is generated.

Method and apparatus for encoding a mesh model, encoded mesh model, and method and apparatus for decoding a mesh model

3D mesh models are widely used in various applications for representing 3D objects. These models are made of vertices and corresponding triangles, which can be compressed based on prediction and residuals. The present invention improves the accuracy of parallelogram prediction, particularly near sharp features. The proposed 3D mesh model encoding comprises analyzing the spatial or dihedral angles between triangles, clustering triangles with similar or equal dihedral angles, and defining a representative dihedral angle for each cluster. Triangles of each cluster are then encoded relative to individual prediction triangles having the representative dihedral angle according to the cluster. Additionally, the prediction triangle may be mirrored. An indication of the encoding mode is inserted into each vertex of the encoded bitstream. A decoder extracts the encoding mode indication, reconstructs the individual prediction triangles based on the respective representative dihedral angles and performs triangle prediction and reconstruction.

Method and apparatus for encoding 3D mesh models, and method and apparatus for decoding encoded 3D mesh models

3D models of the engineering class usually have a large number of connected components, with small numbers of large triangles, often with arbitrary connectivity. To enable compact storage and fast transmission of large 3D mesh models, an efficient compression strategy specially designed for 3D mesh models is provide. A method for encoding a 3D mesh model comprises determining and clustering repeating components, normalizing the components, wherein scaling factors are clustered and orientation axes are clustered, encoding the connected components using references to the clusters, and entropy encoding the connected components.

Compression of 3D meshes with repeated patterns

The invention is made in the technical field of encoding and decoding of bit sequences. The invention proposes a device for compression-encoding an input bit sequence in which Zeroes and Ones occur equally frequent, comprising an XOR gate adapted for receiving pairs of immediately succeeding bits of the input bit sequence as inputs and for outputting further bits of another bit sequence, means for adding a bit to said other bit sequence wherein the added bit is a primary bit which is equal to a primary bit of the input bit sequence or a last bit which is equal to a last bit of the input bit sequence, and means for encoding the other sequence. The XOR gate transforms the input bit sequence into the other bit sequence which comprises more uneven frequencies of occurrence of Zeroes and Ones than the input bit sequence.

Method and device for encoding an input bit sequence and corresponding decoding method and device

A method for compressing a symbol sequence, wherein each symbol may have one out of three or more possible symbol values, said method comprises the steps of modifying the symbol sequence by replacing each run pair, which contains a first run of symbols of a most frequent symbol value and a second run of symbols of a second most frequent symbol value, by a further symbol value not comprised in the three or more possible symbol values, generating a binary sequence comprising all replaced run pairs and compression encoding the binary sequence and the modified symbol sequence.

Method and device for encoding and decoding of symbol sequences wherein each symbol may have one out of three or more possible symbol values

The invention is related to a method and a device for encoding of a bit sequence. Said method comprises generating, for each run of Ones comprised in the bit sequence, a unary representation of length of the respective run of Ones, generating a first sequence by concatenating the generated unary representations of lengths of runs of Ones, generating, for each run of Zeroes comprised in the bit sequence, a unary representation of the length of the respective run of Zeroes, generating a second sequence by concatenating the generated unary representations of lengths of runs of Zeroes, and bit plane encoding the generated first and second sequence of unary representations. In most cases, overall entropy of bit planes of unary representations of run lengths is smaller than entropy of the bit sequence. Thus, more compact encoding can be achieved.

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Beijing, China

Kang Ying Cai