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image acquisition systems are rapidly becoming more affordable, especially systems based on commodity electronic cameras. At the same time, personal computers with graphics hardware capable of displaying complex 3D models are also becoming inexpensive enough to be available to a large population. As a result, there is potentially an opportunity to consider new virtual reality applications as diverse as cultural heritage and retail sales that will allow people to view realistic 3D objects on home computers. Although there are many physical techniques for acquiring 3D data-including laser scanners, structured light and time-of-flight-there is a basic pipeline of operations for taking the acquired data and producing a usable numerical model. We look at the fundamental problems of range image registration, line-of-sight errors, mesh integration, surface detail and color, and texture mapping. In the area of registration we consider both the problems of finding an initial global alignment using manual and automatic means, and refining this alignment with variations of the Iterative Closest Point methods. To account for scanner line-of-sight errors we compare several averaging approaches. In the area of mesh integration, that is finding a single mesh joining the data from all scans, we compare various methods for computing interpolating and approximating surfaces. We then look at various ways in which surface properties such as color (more properly, spectral reflectance) can be extracted from acquired imagery. Finally, we examine techniques for producing a final model representation that can be efficiently rendered using graphics hardware.

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We report a detailed study of the electronic and structural properties of the 39K superconductor MgB 2 and of several related systems of the same family, namely Mg 0.5 Al 0.5 B 2 , BeB 2 , CaSi 2 and CaBeSi. Our calculations, which include zone-center phonon frequencies and transport properties, are performed within the local density approximation to the density functional theory, using the full-potential linearized augmented plane wave (FLAPW) and the norm-conserving pseudopotential methods. Our results indicate essentially three-dimensional properties for these compounds; however, strongly two-dimensional σ-bonding bands contribute significantly at the Fermi level.Similarities and differences between MgB 2 and BeB 2 (whose superconducting properties have not been yet investigated) are analyzed in detail. Our calculations for Mg 0.5 Al 0.5 B 2 show that metal substitution cannot be fully described in a rigid band model. CaSi 2 is studied as a function of pressure, and Be substitution in the Si planes leads to a stable compound similar in many aspects to diborides.