To render an object by ray tracing, one or more rays are shot from the viewpoint through every pixel of the image plane. For reflective and refractive objects, especially for multiple levels of reflections and/or refractions, this requires many expensive intersection calculations. This paper presents a new method for accelerating ray-tracing of reflective and refractive objects by substituting ...

Event count data are distinguished by being positive and integer valued with often small numbers of unique values. Examples include just about anything measured by counts or summary frequency data. Standard ordinary least squares (OLS) regression modeling requires the assumption that the model errors, εi, are independently and identically distributed, (i.i.d.)~ N(0,σ), normal random variables. ...

Ray-based simulations have been shown to generate impressively realistic ultrasound images in interactive frame rates. Recent efforts used GPU-based surface ray-tracing to simulate complex ultrasound interactions such as multiple reflections and refractions. These methods are restricted to perfectly specular reflections (i.e., following only a single reflective/refractive ray), whereas real tis...

In the segmentation of natural images, most algorithms rely on the concept of occlusion. Intuitively, if all of the pixels in a region are the same color, they are probably part of the same object, which is blocking all of the light from the objects behind it. In x-ray images, however, this assumption is violated. In this paper, we introduce SATISφ, a method for separating objects in a set of x...

Resumen. A la hora de abordar la creación de una Biblioteca Digital se deben resolver tres problemas principales: el diseño de una BD que almacene tanto información estructurada como no estructurada (principalmente textos planos e imágenes), el diseño de aplicaciones para la alimentación de la BD y el diseño de interfaces de consulta para acceder a la misma probablemente vía Internet. Unido a t...