Search

The visualization of volumetric datasets, quite common in medical image processing, has started to receive attention fromother communities such as scientific and engineering. The main reason is that it allows the scientists to gain important insights into the data. While the datasets are becoming larger and larger, the computational power does not always go hand to hand, because the requirements of using low-end PCs or mobile phones increase. As a consequence, the selection of an optimal viewpoint that improves user comprehension of the datasets is challenged with time consuming trial and error tasks. In order to facilitate the exploration process, informative viewpoints together with camera paths showing representative information on the model can be determined. In this paper we present amethod for representative viewselection and path construction, togetherwith some accelerations that make this process extremely fast on a modern GPU.

When using data-capture methods designed to retrieve functional information, we may have incomplete morphological information in the presence of desease. This is specially so for SPECT data of an infarcted heart.

Given a client-server communication network, with workstations equipped with 3D texture hardware, we propose a technique that guarantees the optimal use of the client texture hardware. We consider the best representation of a data model that has to be rendered on the client side as the one that requires the minimal texture space while preserving image quality. Taking into account this consideration the basis of the proposed technique is the selection of the best multiresolution representation from a volume hierarchy, maintained by the server. The key points of our proposal are: (i) the hierarchical data structure used, either by the server and the client, to maintain the data; (ii) the data management process applied by the server to satisfy client requirements. (iii) the possibility of the client to predict part of one transmission by analyzing the previous one. Such a capability allows the client to perform some computations in advance and, therefore, reduces frame rates.

The Hybrid Octree (HO) is an octree-based representation scheme for coding in a single model an exact representation of a surface and volume data. The HO is able to efficiently manipulate surface and volume data independently. Moreover, it facilitates the visualization and composition of surface and volume data using graphic hardware. The HO definition and its construction algorithm are provided. Some examples are presented and the goodness of the model is discussed.

This work is focused on the interactive navigation through highly polygon-populated ship environments. A conservative visibility algorithm is presented that hierarchically computes visibility for different observer positions and stores it in a new octree based structure, the Visibility Octree (VO) The VO is used during the navigation. Its main contribution is the ability to provide an effective control over the coarseness of the visibility approximation. Some results are presented for indoor ship scenes that show that the VO is efficient on densely occluded scenes.

Multiresolution models with different levels of detail are a basic tool for handling very large and complex systems in computer aided design applications such as ship design. In this work, we discuss several automatic simplification algorithms that generate a multiresolution family of solid models that approximate with different levels of detail the boundary representation of a given polyhedral solid. Methods based on the simplification of triangular meshes are discussed together with octree based algorithms. Comparison criteria include the possibility of geometry and topology simplification, the availability of approximation bounds and feature preservation.

When scenes with a large number of elements have to be used, it is difficult to do a real time walk-through. An algorithm to compute a weak visibility graph of a large data set based on its discretization by means of a regular uniform grid is introduced. The algorithm computes the visibility graph using a new approach for the cell to cell visibility test and an auxiliary quad-tree to speed up.