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A new system for the construction of highly realistic models of real free-form 3D objects is proposed, based on the integration of several techniques (automatic 3D scanning, inverse illumination, inverse texture-mapping and textured 3D graphics). Our system improves the quality of a 3D model (e.g. acquired with a range scanning device) by adding color detail and, if required, high-frequency shape detail. Detail is obtained by processing a set of digital photographs of the object. This is carried out by performing several subtasks: to compute camera calibration and position, to remove illumination effects obtaining both illumination-invariant reflectance properties and a high-resolution surface normal field, and finally to blend and stitch the acquired detail on the triangle mesh via standard texture mapping. In particular, the smooth join between different images that map on adjacent sections of the surface is obtained by applying an accurate piecewise local registration of the original images and by blending textures. For each mesh face which is on the adjacency border between different observed images, a corresponding triangular texture patch can also be resampled as a weighted blend of the corresponding adjacent image sections. Examples of the results obtained with sample works of art are presented and discussed.

: Multiresolution representations are widely used in many visualization contexts and applications, since they provide optimal management of the data representation by using at each time instant a level of detail most appropriate for the application requirements. Unfortunately, current solutions do not allow the topology of the object to be changed, and this tends to prevent its adoption in applications where topological changes are needed, such as virtual surgery applications. By extending a known multiresolution model based on simplicial complexes, we develop a new approach which supports dynamic topological modifications of the represented object without greatly increasing the representation complexity.

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This prospective, multicenter, epidemiological study was carried out in 99 Italian ICUs, distributed throughout the country, from April 1993 to March 1994. In the study, we applied the new ACCP/SCCM classification system for sepsis (SIRS, sepsis, severe sepsis and septic shock) and determined the prevalence, incidence, evolution and outcome of these categories in critically ill patients. The preliminary analysis of 1101 patients showed that on admission SIRS accounted for about half of the diagnoses (52%) with sepsis, severe sepsis and septic shock accounting for 4.5%, 2.1% and 3% of patients, respectively. Patients with severe sepsis or septic shock more frequently had high SAPS scores than patients without sepsis. Mortality rates were similar in patients with SIRS (26.5%) and without SIRS or infection (24%), but rose to 36% in patients with sepsis, to 52% in those with severe sepsis and to 81.8% in those with septic shock. Sepsis, severe sepsis and septic shock were more common in patients with medical diagnoses, and neither severe sepsis nor septic shock was observed in trauma patients. With respect to evolution, the incidence of septic shock was progressively higher in patients admitted with more severe “sepsis-related” diagnoses, while only a trivial difference in rates of incidence was observed between SIRS patients and those admitted without SIRS or any septic disorder (nil). The breakdown of the various ACCP/SCCM “sepsis-related” diagnoses at any time during the study was: SIRS in 58% of the population, sepsis in 16.3%, severe sepsis in 5.5% and septic shock in 6.1%. It seems reasonable to expect from the final evaluation of our study answers to the questions raised by the ACCP/SCCM Consensus Conference about the correlations between “sepsis-related” diagnosis, severity score, organ dysfunction score and outcome.

In this paper we address the problem of computing visibility information on digital terrain models in parallel. We propose a parallel algorithm for computing the visible region of an observation point located on the terrain. The algorithm is based on a sequential triangle-sorting visibility approach proposed by De Floriani et al. (1989). Static and dynamic parallelization strategies, both in terms of partitioning criteria and scheduling policies, are discussed. The different parallelization strategies are implemented on an MIMD multicomputer and evaluated through experimental results.

Very large graphics models are common in a number of applications, and many different simplification methods have recently been developed. Some of them support the construction of multiresolution representations of the input meshes. On the basis of these innovative techniques, we foresee a modeling framework based on three separate stages (shape modeling, multiresolution encoding, and resolution modeling), and propose a new approach to the last stage,resolution modeling, which is highly general, user-driven, and not strictly tied to a particular simplification method. The approach proposed is based on a multiresolution representation scheme for triangulated, 2-manifold meshes, the Hypertriangulation Model (HyT). This scheme allows selective “walks” along the multiresolution surface, moving between adjacent faces efficiently. A prototypalresolution modelingsystem,Zeta, has been implemented to allow interactive modeling of surface details and has been evaluated on several practical models. It supports the efficient extraction of fixed resolution representations; unified management of selective refinements and selective simplifications; easy composition of the selective refinement/simplification actions, with no cracks in the variable resolution mesh produced; multiresolution editing; and interactive response times.

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AbstractA technique to triangulate planar convex polygons having T-vertices is described. Simple strip or fan tessellation of a polygon with T-vertices can result in zero-area triangles and compromise the rendering process. Our technique splits such a polygon into one triangle strip and, at most, one triangle fan. The technique is particularly useful in multiresolution or adaptive representation of polygonal surfaces and the simplification of surfaces.

AbstractThis paper proposes a computer-oriented interpretation of the laws ruling the elevation of figures in bas- or high-relief sculptures. It presents some simple algorithms and a prototypical, public-domain software tool for the generation of three-dimensional bas- and high-reliefs starting from three-dimensional surface models.

A simple technique to visualize the isosurfaces extracted from a cell-based volumetric dataset using the Marching Cubes algorithm is proposed. The technique exploits the intrinsic ordering of the triangles produced by the surface extraction algorithm by adopting a Back-to-Front visualization technique. The use of the technique together with the adoption of a simple shading algorithm permits the rendering of high resolution volumetric datasets in computational environments with limited capabilities in terms of memory and graphics hardware.Copyright 1994, 1999 Academic Press, Inc.