To improve the visualization of large 3D landscapes and city models in a network environment, the authors use two different types of hierarchical level-of-detail models for terrain and groups of buildings. They also leverage the models to implement progressive streaming in both client-server and peer-to-peer network architectures.

International audienceAn analysis and discussion on the relevance of various wavelet schemes for hologram compression and reconstruction when the rendering configuration makes it possible to exploit selective refinements to perform a viewpoint-based degraded reconstruction. It is observed that Gabor wavelet bases have better time-frequency localization as compared to Fresnelet bases and hence are well suited for view-dependent compression techniques for hologram reconstruction

With the recent widespread interest for head-mounted displays applied to virtual or augmented reality, holography has been considered as an appealing technique for a revolutionary and natural 3D visualization system. However, due to the tremendous amount of data required by holograms and to the very different properties of holographic data compared to common imagery, compression of digital holograms is a highly challenging topic for researchers. In this study, we introduce a novel approach, to the best of our knowledge, for color hologram compression based on matching pursuit using an overcomplete Gabor's dictionary. A detailed framework, together with a GPU implementation, from hologram decomposition to bitstream generation, is studied, and the results are discussed and compared to existing hologram compression algorithms.

Integral imaging is an attractive auto-stereoscopic three dimensional (3D) technique for next generation 3DTV. To improve its video quality, new techniques are required to effectively compress the huge volume of integral image (II) data. In this paper, a new compression method implemented by multi-view video coding (MVC) is provided and used for sub-images (SI). SI is an alternative form of 2D image transformed from original II. Each SI represents the 3D scene from parallel viewing directions and contains superior compression capabilities than original captured elemental images (EI). For this reason, we consider arranging the group of SIs as the format of multi-view video (MVV) and then encode the generated MVV by MVC standard. Experimental results show that our proposed compression approach improves the compression efficiency when compared to the traditional MPEG-4/AVC compression method for II.

A hybrid approach for fast occlusion processing in computer-generated hologram calculation is studied in this paper. The proposed method is based on the combination of two commonly used approaches that complement one another: the point-source and wave-field approaches. By using these two approaches together, the proposed method thus takes advantage of both of them. In this method, the 3D scene is first sliced into several depth layers parallel to the hologram plane. Light scattered by the scene is then propagated and shielded from one layer to another using either a point-source or a wave-field approach according to a threshold criterion on the number of points within the layer. Finally, the hologram is obtained by computing the propagation of light from the nearest layer to the hologram plane. Experimental results reveal that the proposed method does not produce any visible artifact and outperforms both the point-source and wave-field approaches.

Guaranteeing interoperability between devices and applications is the core role of standards organizations. Since its first JPEG standard in 1992, the Joint Photographic Experts Group (JPEG) has published several image coding standards that have been successful in a plethora of imaging markets. Recently, these markets have become subject to potentially disruptive innovations owing to the rise of new imaging modalities such as light fields, point clouds, and holography. These so‐called plenoptic modalities hold the promise of facilitating a more efficient and complete representation of 3D scenes when compared to classic 2D modalities. However, due to the heterogeneity of plenoptic products that will hit the market, serious interoperability concerns have arisen. In this paper, we particularly focus on the holographic modality and outline how the JPEG committee has addressed these tremendous challenges. We discuss the main use cases and provide a preliminary list of requirements. In addition, based on the discussion of real‐valued and complex data representations, we elaborate on potential coding technologies that range from approaches utilizing classical 2D coding technologies to holographic content‐aware coding solutions. Finally, we address the problem of visual quality assessment of holographic data covering both visual quality metrics and subjective assessment methodologies.

Wavelet methods for geometry encoding is a recently emerged supenet of multiresolution analysis which has proven to be very efficient in term of compression and adaptive transmission of 3D content. The decorrelating power and spacelscale localization of wavelets enable efficient compression of arbitrary meshes as well as progressive and local reconstruction. Recent techniques based on zerowee compressiun have shown to be among the best lossy mesh compression methods, while remaining compatible with selective transmission of geometric data at various level of detail. While some progressive reconstmction schemes have been propored in the past. we show in this paper that this representation. recently proposed in the MPEG4 standard. can be efficiently used to perfom real-time. view-dependent reconstruction of large meshes. The proposed system combines algorithms for local updates. cache management and serverlclient dialog. The local details management is an improvement of progressive reconstructions built on top of hierarchical structures. It enables fast. homogeneous accommodation and suppression of wavelet coefficients at any level of subdivision. with time complexity independent of the size of the reconstructed mesh. The cache structure wisely exploits the hierarchical character of the received data. in order lo avoid redundant information transmission. The whole system enables the client to have total control on the quality of navigation according to its storage and processing capabilities. whatever the size of the mesh.

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