Yair Kurzion

An accurate method for voxelizing polygon meshes

The process of generating discrete surfaces in a volumetric representation, termed voxelization, is confronted with topological considerations as well as accuracy and efficiency requirements. The authors introduce a new method for voxelizing planar objects which, unlike existing methods, provides topological conformity through geometric measures. They extend their approach to provide, for the first time, an accurate and coherent method for voxelizing polygon meshes. This method eliminates common voxelization artifacts at edges and vertices. They prove the methods topological attributes and report performance of their implementation. Finally, they demonstrate that this approach forms a basis for a new set of voxelization algorithms by voxelizing an example cubic object.

Design of accurate and smooth filters for function and derivative reconstruction

The correct choice of function and derivative reconstruction filters is paramount to obtaining highly accurate renderings. Most filter choices are limited to a set of commonly used functions, and the visualization practitioner has so far no way to state his preferences in a convenient fashion. Much work has been done towards the design and specification of filters using frequency based methods. However for visualization algorithms it is more natural to specify a filter in terms of the smoothness of the resulting reconstructed function and the spatial reconstruction error. Hence, the authors present a methodology for designing filters based on spatial smoothness and accuracy criteria. They first state their design criteria and then provide an example of a filter design exercise. They also use the filters so designed for volume rendering of sampled data sets and a synthetic test function. They demonstrate that their results compare favorably with existing methods.

Interactive space deformation with hardware-assisted rendering

The authors introduce a new approach for the deformation of surface and raster models in two and three dimensions. Rather than deforming the model, they deform the agents employed to render it. The method uses one deformation tool (the deflector) to deform any object that is ray traceable. Based on deforming the rendering primitives rather than objects, the approach invests computation effort only in those regions of the model that contribute to the final image.

Space Deformation using Ray Deflectors

In this paper we introduce a new approach to the deformation of surface and raster models in two and three dimensions. Rather then deforming the objects in the model, we deform the rays used to render the scene. The mechanism to specify the deformation, which we call a deflector, is a vector of gravity positioned in space. This gravity vector bends any ray that travels through its field of gravity in a view-independent fashion. Images generated by these curved rays give the impression of a deformed space. Unlike previous methods that deform all the objects in the scene, our approach deforms only those parts of the model that contribute to the final image. In addition, using deflectors, our approach can deform any object type that can be rendered by a ray casting algorithm, providing a unified solution to space deformation.

Building a virtual environment for endoscopic sinus surgery simulation

Abstract Advanced display technologies have made the virtual exploration of relatively complex models feasible in many applications. Unfortunately, only a few human interfaces allow natural interaction with the environment. Moreover, in surgical applications, such realistic interaction requires real-time rendering of volumetric data—placing an overwhelming performance burden on the system. We report on our advances towards developing a virtual reality system that provides intuitive interaction with complex volume data by employing real-time realistic volume rendering and convincing forece feedback (haptic) sensations. We describe our methods for real-time volume rendering, model deformation, interaction, and the haptic devices, and demonstrate the utilization of this system in the real-world application of Endoscopic Sinus Surgery (ESS) simulation.

Grouping volume renderers for enhanced visualization in computational fluid dynamics

This paper advocates the use of a group of renderers rather than any specific rendering method. We describe a bundle containing four alternative approaches to visualizing volume data. One new approach uses realistic volumetric gas rendering techniques to produce photo-realistic images and animations. The second uses ray casting that is based on a simpler illumination model and is mainly centered around a versatile new tool for the design of transfer functions. The third method employs a simple illumination model and rapid rendering mechanisms to provide efficient preview capabilities. The last one reduces data magnitude by displaying the most visible components and exploits rendering hardware to provide real time browsing capabilities. We show that each rendering tool provides a unique service and demonstrate the combined utility of our group of volume renderers in computational fluid dynamic (CFD) visualization. While one tool allows the explorer to render rapidly for navigation through the data, another tool allows one to emphasize data features (e.g., shock waves), and yet another tool allows one to realistically render the data. We believe that only through the deployment of groups of renderers will the scientist be well served and equipped to form numerous perspectives of the same dataset, each providing different insights into the data. >

Volume rendering methods for computational fluid dynamics visualization

The paper describes three alternative volume rendering approaches to visualizing computational fluid dynamics (CFD) data. One new approach uses realistic volumetric gas rendering techniques to produce photo-realistic images and animations from scalar CFD data. The second uses ray casting that is based an a sampler illumination model and is mainly centered around a versatile new tool for the design of transfer functions. The third method employs a simple illumination model and rapid rendering mechanisms to provide efficient preview capabilities. These tools provide a large range of volume rendering capabilities to be used by the CFD explorer to render rapidly for navigation through the data, to emphasize data features (e.g., shock waves) with a specific transfer function, or to present a realistic rendition of the model.<<ETX>>

Multisensory platform for surgical simulation

Advanced display technologies have made the virtual exploration of relatively complex models feasible in many applications. Unfortunately, only a few human interfaces allow natural interaction with the environment. Moreover in surgical applications, such realistic interaction requires real time rendering of volumetric data-placing an overwhelming performance burden on the system. We report on a collaboration of a unique interdisciplinary group developing a virtual reality system that provides intuitive interaction with complex volume data by employing real time realistic volume rendering and convincing force feedback (haptic) sensations. We describe our rendering methods and the haptic devices in detail and demonstrate the utilization of this system in the real world application of Endoscopic Sinus Surgery (ESS) simulation.

Size preserving pattern mapping

We introduce a new approach for mapping texture on volumetric iso-surfaces and parametric surfaces. Our approach maps 2D images on surfaces while maintaining continuity and preserving the size of the mapped images on the models. Our approach is fully automatic. It eliminates the need for manual mapping of texture maps. We use the curvature of a surface at a point in order to continuously vary the scale of the mapped image. This makes our approach dependent only on local attributes of a point (position, normal and its derivatives) and independent of the global shape and topology of an object. Our method can map high resolution images on low resolution volumes, hence enhancing the visual appearance of rendered volume data. We describe a general framework useful for all surface types that have a C/sup 1/ continuous normal. We demonstrate the new method for painting volume data and for mapping cavities on volume data.