KEYWORDS: Mobile devices, 3D modeling, Image processing, Multimedia, Electronic imaging, Personal digital assistants, Cell phones, 3D image processing, Head, Solid modeling
The enormous spread of mobile computing devices (e.g. PDA, cellular phone, palmtop, etc.) emphasizes scalable applications, since users like to run their favorite programs on the terminal they operate at that moment. Therefore appliances are of interest, which can be adapted to the hardware realities without loosing a lot of their functionalities. A good example for this is "Facial Animation," which offers an interesting way to achieve such "scalability." By employing MPEG-4, which provides an own profile for facial animation, a solution for low power terminals including mobile phones is demonstrated. From the generic 3D MPEG-4 face a specific 2D head model is derived, which consists primarily of a portrait image superposed by a suited warping mesh and adapted 2D animation rules. Thus the animation process of MPEG-4 need not be changed and standard compliant facial animation parameters can be used to displace the vertices of the mesh and warp the underlying image accordingly.
The ultimate goal for future telecommunication is highly effective inter-personal information exchange. The effectiveness of telecommunication is greatly enhanced by 3-D telepresence. This requires that visual information is presented in such a way that the viewer is under the impression of actually being physically close to the party with whom the communication takes place. One way to achieve a natural 3-D impression is to encode image sequences using 3-D model objects and animate them again by computer graphic means regarding the observers eye positions. This concept will use a parametric 3-D scene description in order to model a scene. The parameters of the model objects will be estimated from trinocular input image sequences by means of image analysis. This paper starts with an overview on the European ACTS project PANORAMA, in which the above mentioned concept will be realized and evaluated. In the main part the shape initialization of physical objects from a multiview image sequence will be discussed. For this the range information given by three disparity maps from different stereo views is backprojected into 3-D space. The resulting cloud of 3-D points is then approximated by a flexible triangular net by using a technique named discrete smooth interpolation. The discrete smooth interpolation is a particular surface interpolation technique, which is solved by an iterative approach. It allows to generate a surface, defined as a wireframe mesh, that fits (or interpolates) a given set of 3D points by observing, at the same time, some given constraints about the surface characteristics, like roughness, behavior at the boundaries, etc. The finally presented results show the capabilities of this approach in video communication.
An ultimate goal for future telecommunication applications is giving the viewer the feeling of being present in the scene, or short 3-D telepresence. One way to achieve a natural 3-D impression is to encode image sequences using 3-D model objects and animate them again by computer graphic means regarding the observers' eye positions. A crucial task within such a system is the estimation of 3-D shape parameters based on range information derived from disparity estimation between two or more cameras. The contribution describes a new approach to create a triangulated irregular net over a given region in a depth map. It attaches more importance to rendering aspects regarding texture mapping than to spatial accuracy. The shape estimation starts with the polygonalization of the region boundary, which describes a curve in 3-D space. After projecting the polygon into the image plane a constrained, quality conforming Delaunay triangulation is executed in the image plane. This forces the triangulation to insert all segments of the projected boundary polygon into the mesh and not to create any triangle exceeding a certain area. Finally the triangles of the net are subdivided recursively further, until an approximation criteria depending on the local curvature of the depth map is reached.
A new coding scheme for partially computer-rendered image sequences will be presented. It is specifically suited for heterogeneous data sets containing symbolic and pixel-based image descriptions, which are used by an electronic set system at the receiver site for the synthesis and mixture of transmitted image sequences. The different types of data sets and their particular properties regarding data compression are explained. Finally, results are given comparing the new coding scheme with traditional MPEG2 coding based on typical test sequences.
KEYWORDS: Image compression, Cameras, 3D modeling, Data modeling, Computer programming, Receivers, Computer graphics, Solid modeling, Signal to noise ratio, Data compression
A new coding scheme for combined natural and computer rendered image sequences is presented. It is specifically suited for the heterogeneous data sets used by an electronic set system at the receiver site for the synthesis and mixture of transmitted image sequences. The different types of data sets and their particular properties regarding data compression are explained. Finally, results are given comparing the new coding scheme with traditional MPEG2 coding based on typical test sequences.
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