Catálogo de publicaciones - libros

Multiresolution meshes enable us to build representations of geometric objects at different Levels of Detail (LODs). We introduce a multiresolution scheme whose data structure allows us to separately restore the geometry and topology of a mesh during the refinement process. Additionally, we use a topological criterion (not a geometric criterion, as usual in the literature) to quickly simplify a mesh, what seems to make the corresponding simplification algorithm adequate for real-time applications such as, for example, on-line computer games.

This work concerns the problem of curve and surface fitting. In particular, we focus on the case of 3D point clouds fitted with Bézier curves and surfaces. Because these curves and surfaces are parametric, we are confronted with the problem of obtaining an appropriate parameterization of the data points. On the other hand, the addition of functional constraints introduces new elements that classical fitting methods do not account for. To tackle these issues, two Artificial Intelligence (AI) techniques are considered in this paper: (1) for the curve/surface parameterization, the use of genetic algorithms is proposed; (2) for the functional constraints problem, the functional networks scheme is applied. Both approaches are combined with the least-squares approximation method in order to yield suitable methods for Bézier curve and surface fitting. To illustrate the performance of those methods, some examples of their application on 3D point clouds are given.

The 3D surface textures of skin are important for both visual and tactile inspection. The information of surface textures can aid the inclusion of haptic technology in tele-dermatology as well as enhance the effectiveness of current 2D based applications. This work aims to analyse and model surface textures of skin including diseased skin. For this purpose the multiple pairwise pixel interaction model of Markov-Gibbs Random Field (MGRF) has been used. Surface textures are in the form of 3D mesh which are converted to 2D height maps and modeled as grayscale textures. The results demonstrate that homogenous stochastic textures of skin can be modeled successfully. The successfully modeled textures represent the surface irregularities on scale of 0.1 mm which can create the tactile perception of roughness for skin in haptic applications.

3D shape matching plays an important role in a 3d shape search system. Users generally want to query by sketch in a 3d shape search system rather than query by example or strings. Some interfaces with query by sketch are developed. Although they have some advantages, their limitations exist. In this paper, we present a new sketch-based query interface for spherical sectioning based shape descriptor. Since spherical sectioning based shape descriptor use the slice patterns of the original model, user-inputted 2d sketch based query is easily converted into the value from spherical sectioning descriptor. This helps to develop more powerful interface in intuitive user’s style. For the validity of our method, we show the experimental results.

A new algorithm of view synthesis from serial images taken by camera motion based on edge information is proposed in this paper. Firstly, the edges in images are extracted and divided into line segments. From the information of relative positions and orientations of those lines, the corresponding lines between two views are detected. Secondly, we process the smooth region of the images. Finally, a destination image can be generated followed by interpolation of the corresponding points. By this method, we can create a clear edge image and therefore obtain a better destination digital image.

Diffusion tensor imaging (DTI) is an extension of the conventional magnetic resonance imaging with the capability to characterize the diffusion behavior of water in a tissue. The study of DTI and its visualization has become an emerging focus of research in brain studies since it provides the information required to reconstruct white matter fiber paths. In this paper, we present DTIWeb, a robust, portable and extensible Java application for visualizing and processing DTI data. The proposed framework is based on the Java3D programming platform that provides and object-oriented programming model and independence of computer hardware configuration and operating system. The platform is designed to work through the world wide web and only requires a web browser.

Monte Carlo is the only choice of physically correct method to compute the problem of global illumination in the field of realistic image synthesis. Reusing light transport paths is an interesting and effective tool to eliminate noise, which is one of the main problems of Monte Carlo based global illumination algorithms, such as Monte Carlo ray tracing. But reusing paths technique tends to group spike noise to form noise patches in the images. We propose an alternative way to implementing the reuse of paths to tackle this problem in this paper. Experimental results show that our new way is very promising.

In sensor networks, the sink can move to gather data from sensor nodes. When the mobile sink moves in network area, the connection from the source sensor nodes can be continuously changed. Hence, the routing scheme to changing routing is needed for the connection maintenance. In this paper, we propose a routing scheme for the mobile sink which continuously moves in network area. By the simulation, we analyze the proposed scheme performance to the energy consumption.

HMIPv6 supports the transmission delay between mobile node and correspondent node, handoff signaling and data transmission as introducing an local Home Agent(HA) of new type called MAP(Mobility Anchor Point). Mobile network may generate not only the nested mobile network structure but also a single network because of the node mobility or router mobility. Many subnet exist and several mobile routers or mobile nodes operate in the nested mobile network. This paper proposes the ERD method that a packet entering from MAP to MAP domain decides the explicit routing for correspondent destination node through changing the binding cache structure of MAP domain. We can decrease in quantity of unnecessary packets if we transmit a packet in MAP using ERD method and also reduce an transmission delay because an intermediate mobile router can re-transmit a packet using just the simple packet substitution.

This work provides a performance characterization of three types of transmissions: upstream, downstream and wireless-to-wireless in an infrastructure network based on IEEE 802.11 a/b/g wireless LAN. Measures were carried out on a test-bed which reproduces on a small scale, a real prototype of such a network. When a PDA is mainly used for downloading data from its stationary server, i.e., a desktop PC, a PC and a PDA acts as a fast sender and a slow receiver, respectively, due to substantial differences in their computational capabilities. Thus, we propose two distinct methods for improving the performance during downstream. First, by increasing the size of a receive buffer for a PDA the congestion window size of TCP becomes more stable. Second, a pre-determined delay between packets to be transmitted at the sender should be given. From the performance point of view a method of buffer sizing is preferred rather than adjusting the inter-packet delay. However, such a delay reduces the number of erroneous packets remarkably.