Volume Rendering

Traumatic head injuries can cause internal bleeding within the brain. The resulting hematoma can elevate intracranial pressure, leading to complications and death if left untreated. A craniotomy may be required when conservative measures are ineffective. To augment conventional surgical training, a Virtual Reality-based intracranial hematoma simulator is being developed. A critical step in performing a craniotomy involves cutting burrholes in the skull. This paper describes volumetric-based haptic and visual algorithms developed to simulate burrhole creation for the simulator. The described algorithms make it possible to simulate several surgical tools typically used for a craniotomy.

We present the concept of volumetric depth-peeling. The proposed method is conceived to render interior and ex-terior iso-surfaces for a fixed iso-value and to blend them without the need to render the volume multiple times. The main advantage of our method over pre-integrated ...

Potential applications of volume rendering in musculo-skeletal disorders Three dimensional imaging is increasingly important for evaluation of anatomic relationships and extent of disease, for treatment planning and for follow-up evaluation. The volume rendering technique allows creation of accurate 3D images that can be used for several clinical applications especially in musculo-skeletal disorders such as evaluation of tumors or fractures. This

This paper discusses the problem of subdividing meshes containing tetrahedra, pyramids, prisms or hexahedra into a consistent set of tetrahedra. This problem occurs in computer graphics where meshes with pyramids, prisms or hexahedra must be subdivided into tetrahedra to use efficient algorithms for volume rendering, iso-contouring and particle advection. Another application is for the use of some tetrahedral finite element solvers on a non tetrahedral mesh, or even an hybrid mesh. Arbitrary splitting of quadrilateral faces into two triangles has two major drawbacks: it can lead to discontinuities across element faces, resulting in non conformal meshes, and the subdivision of some elements into tetrahedra may need to introduce new vertices. The algorithms presented in this paper split each quadrilateral face of pyramids, prisms and hexahedra in a consistent way that preserves the conformity of the mesh. Elements are subdivided into tetrahedra without introducing new vertices. The al...

Este trabajo presenta en detalle la teoría necesaria para comprender e implementar la técnica de rendering directo de volúmenes (direct volume rendering). Esto incluye la derivación paso a paso de la ecuación de composición volumétrica, y su implementación en los algoritmos de ray casting, planos alineados, conchas esféricas y shear-warp. Aborda también la clasificación pre-integrada, la cual mejora la calidad del rendering con poco impacto en el tiempo de respuesta, así como la inclusión de una luz externa para la iluminación.

Philippe Lacroate en 1995 logró diseñar e implementar el primer algoritmo de visualización volumétrica en tiempo real, que generaba una imagen por segundo en una plataforma Silicon Graphics, utilizando la factorización Shear-Warp. En este trabajo se presentan detalles de implementación del Shear-Warp, que permiten mejorar la calidad de la imagen en tonos de grises, y obtener un tiempo de respuesta adecuado, generando hasta diez imágenes por segundo en una estación NT, y hasta tres en un PC de bajo costo. Entre los detalles merecen citarse la cuantización de normales vía subdivisión de un icosahedro, mejoras en la estructura de datos de la imagen intermedia, e implementación del warping en dos versiones: usando el hardware gráfico vía texture mapping, y en software mediante un algoritmo incremental.

Volume rendering is an important area of study in computer graphics, due to its application in areas such as medicine, physic simulations, oil and gas industries, and others. The main used method nowadays for volume rendering is ray casting. Nevertheless, there are a variety of parallel APIs that can be used to implement it. Thus, it is important to evaluate the performance of ray casting in different parallel APIs to help programmers in selecting one of them. In this paper, we present a performance comparison using OpenGL ® with fragment shader, OpenGL ® with compute shader, OpenCL, and CUDA.

Being able to create insightful visualizations from both simulated and measured data is important for the visualization community. For scalar volumes, direct volume rendering has proved a useful tool for data exploration. Using a transfer function, we can map scalar values to colors and opacities to identify and enhance important features. Although researchers have developed some automatic techniques for transfer-function specification, the exploration process still requires users to tune the parameters manually until they can produce the desired visualization. Researchers have conducted substantial work to assist users in this specification task by providing interactive widgets. These tools generally assist users by letting them create and manipulate widgets over one or more dimensions of histogram information representing the data. The authors' framework combines elements of existing transfer-function specification techniques and introduces new features to handle the direct volume rendering of a diversity of volumetric data sets.