A progressive 3D mesh coding scheme using the octree-based space
partitioning is proposed in this work, which achieves better coding
efficiency than the state-of-the-art kd-tree-based codec. Given a 3D mesh, the quantized 3D vertices are first partitioned into an octree structure. The octree is then traversed from the root and gradually to the leaves. During the traversal, each 3D cell in the tree front is subdivided into eight child cells through three orthogonal cell bi-partitionings. For each cell subdivision, the information of nonempty child cells is encoded. To encode the information, two approaches (i.e. the bit-pattern coding approach and the nonempty-child-cell-tuple coding approach) are implemented and compared. In addition to the geometry coding, the local connectivity update associated with each cell subdivision is also encoded. Furthermore, selective cell subdivision is performed in the tree front to provide better rate-distortion performance, especially at low bitrates. It is shown in experimental results that the geometry coding cost is around 4.2 bits per vertex (bpv) for 8-bit coordinate quantization and 14.3 bpv for 12-bit coordinate quantization, and the connectivity coding cost is 3.3 bpv on the average.
Progressive coding of 3D textured graphic models using a joint mesh-texture optimization technique is investigated in this work. The mesh and texture data of a model are first fed into their respective compression modules to result in a series of levels of details. Then, for a given viewpoint, a rate-distortion surface is generated using these mesh and texture data. Afterwards, an optimal path over the rate-distortion surface is determined by the steepest descent algorithm. To achieve progressive transmission, the mesh and texture are transmitted in a certain ratio along the optimal path to provide the best visual quality for the given viewpoint. For further generalization, a layered sampling algorithm is proposed to deal with an arbitrary viewing angle. The performance of the proposed joint mesh-texture progressive coding algorithm is demonstrated by experimental results.
An Internet-based interactive walkthrough virtual environment is
presented in this work to facilitate interactive streaming and
browsing of 3D graphic models across the Internet. The models are
compressed by the view-dependent progressive mesh compression
algorithm to enable the decorrelation of partitions and finer
granularity. Following the fundamental framework of mesh
representation, an interactive protocol based on the real time
streaming protocol (RTSP) is developed to enhance the interaction
between the server and the client. Finally, the data of the
virtual world is re-organized and transmitted according to the
viewer's requests. Experimental results demonstrate that the
proposed algorithm reduces the required transmission bandwidth,
and provides an acceptable visual quality even at low bit rates.
A view-dependent progressive mesh coding algorithm is proposed in this work to facilitate interactive 3D graphic streaming and browsing. First, a 3D graphic model is split into several partitions. Second, each partition is simplified independently to generate a base model that can be efficiently encoded. Third, topological and geometrical data are reorganized to enable the view dependent transmission. Before the transmission, the server is informed of the viewing parameters. Then, the server can accordingly transmit visible parts in detail, while cutting off invisible parts. Experimental results demonstrate that the proposed algorithm reduces the required transmission bandwidth, and provides an acceptable visual quality even at low bit rates.
A view-dependent progressive mesh (VDPM) coding algorithm is proposed in this research to facilitate interactive 3D graphics streaming and browsing. The proposed algorithm splits a 3D graphics model into several partitions, progressively compresses each partition, and reorganizes topological and geometrical data to enable the transmission of visible parts with a higher priority. With the real-time streaming protocol (RTSP), the server is informed of the viewing parameters before transmission. Then, the server can adaptively transmit visible parts in detail, while cutting off invisible parts. Experimental results demonstrate that the proposed algorithm reduces the required transmission bandwidth, and exhibits acceptable visual quality even at low bit rates.