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.