| Free Image-Based Virtual Space (FIBVS) is a kind of virtual space, which supports free walkthrough by organizing real world images or videos captured by cameras.Compared with traditional geometry-based virtual space, image-based virtual space (IBVS) has some advantages: constructing easily, rendering fast and reality, et al. However, the free degree of IBVS is limited by real images. How to walk freely in IBVS is a key issue of the research of IBVS construction, so this thesis puts more concerns on it. The main contents and contributions of the dissertation include:(1) We put forward a kind of theory and some techniques for FIBVS to achieve free walkthrough. We study the characteristics, types, components, space organization and manipulation of FIBVS, and solve the problems of free walkthrough, manipulation of image-based virtual objects, and extraction of all kinds of multimedia information.(2) To solve the limitation of the viewing range of cylindrical IBVS, we study approaches of constructing spherical IBVS, which support the observation to the IBVS from all directions. One way is based on synthetic scenes. We study the methods of shooting scenes, constructing and storing spherical panoramic images, and looking scenes. Under these methods, we have constructed spherical IBVS by synthetic scenes images, in which the requirement of looking straight up or down is satisfied. The other way is based on real scenes. We study how to shoot scenes with fisheye lens, analyze the projection model of fisheye lens, and provide a method of building spherical panaromic images with fisheye images. With this method, we have constructed spherical IBVS by real scenes images.(3) To increase the vertical viewing range during free walkthrough, we put forward new spherical-based conspherical mosaics on the basis of concentric mosaics. Under synthetic scenes and real scenes, we study the approaches of shooting scenes, constructing conspherical mosaics and walking freely. We have achieved free walkthrough. Moreover, we analyze the problems of conspherical mosaics, and provide the methods of resolution. Because the amount of data in conspherical mosaics is very large, we also study the compression method in order to satisfy rendering scenes in real time during free walkthrough.(4) We study how to construct dynamical IBVS, and establish a temporal-spatial relation model of moving 3D virtual objects and viewpoint. This work is the theoretical basis of walking freely in dynamical IBVS.(5) We have designed and developed a prototype system of FIBVS ?FVS. With FVS system, users can construct IBVS, walk freely in it, view the scenes from all directions and observe the shelter relation between objects and lighting changes in scenes.
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