Lisa M. Sobierajski

A haptic interaction method for volume visualization

Volume visualization techniques typically provide support for visual exploration of data, however additional information can be conveyed by allowing a user to see as well as feel virtual objects. We present a haptic interaction method that is suitable for both volume visualization and modeling applications. Point contact forces are computed directly from the volume data and are consistent with the isosurface and volume rendering methods, providing a strong correspondence between visual and haptic feedback. Virtual tools are simulated by applying three-dimensional filters to some properties of the data within the extent of the tool, and interactive visual feedback rates are obtained by using an accelerated ray casting method. This haptic interaction method was implemented using a PHANToM haptic interface.

Volumetric ray tracing

This paper presents an eficient ray tracing method for scenes containing volumetric as well as geometric data. A global illumination equation is developed for this method, which is able to capture in a single image both realistic eaects and practical volume rendering. In this method, ray-object intersection calculations result in standard intersection points, as well as intersection segments. For accuracy and eflciency, all objects along a ray are sorted according to distance and intersection classification before any intersection calculations are pelformed. The intersection results are then passed to a shaden which evaluates the intensity equation defined by the illumination model to determine the final pixel value.

Towards a comprehensive volume visualization system

The VolVis system has been developed to satisfy the diverse requirements of the volume visualization community by comfortably housing numerous visualization algorithms and methods within a consistent and well organized framework. The VolVis system is supported by a generalized abstract model which provides for both geometric and volumetric constructs. VolVis contains several rendering algorithms that span the speed versus accuracy continuum. A fast volume rendering algorithm has been developed, which is capable of exploiting existing graphics hardware without placing any viewing restrictions or compromising accuracy. In addition, VolVis includes a volumetric navigation facility, key-frame animation generator, quantitative analysis tools, and a generalized protocol for communicating with 3D input devices.<<ETX>>

VolVis: a diversified volume visualization system

VolVis is a diversified, easy to use, extensible, high performance, and portable volume visualization system for scientists and engineers as well as for visualization developers and researchers. VolVis accepts as input 3D scalar volumetric data as well as 3D volume-sampled and classical geometric models. Interaction with the data is controlled by a variety of 3D input devices in an input device-independent environment. VolVis output includes navigation preview, static images, and animation sequences. A variety of volume rendering algorithms are supported ranging from fast rough approximations, to compression-domain rendering, to accurate volumetric ray tracing and radiosity, and irregular grid rendering.<<ETX>>

A hardware acceleration method for volumetric ray tracing

We present an acceleration method for volumetric ray tracing which utilizes standard graphics hardware without compromising image accuracy. The graphics hardware is employed to identify those segments of each ray that could possibly contribute to the final image. A volumetric ray tracing algorithm is then used to compute the final image, traversing only the identified segments of the rays. This technique can be used to render volumetric isosurfaces as well as translucent volumes. In addition, this method can accelerate the traversal of shadow rays when performing recursive ray tracing.

A fast display method for volumetric data

Presented is a fast display method for volumetric data sets, which involves a slicebased method for extracting potentially visible voxels to represent visible surfaces. For a given viewing direction, the number of visible voxels can be trimmed further by culling most of the voxels not visible from that direction. The entire 3D array of voxels is also present for invasive operations and direct access to interior structures. This approach has been integrated on a low-cost graphic engine as an interactive system for craniofacial surgical planning that is currently in clinical use.

Visualization of calcium activity in nerve cells

Calcium plays an important role in many cellular functions. This investigation of its role in nervous system behavior uses imaging techniques, confocal microscopy, and the VolVis volume visualization system. The use of VolVis provided substantial assistance in the study of cellular calcium dynamics and in monitoring neural network activity. It yielded geometric details that facilitated our understanding of the behavior of calcium indicators inside nerve cells and led to a new view of the calcium permeability of the nuclear envelope. It has also produced anatomical details that significantly facilitated the development of a technique to directly visualize the activity of neuron populations while simultaneously observing vertebrate behavior. >

Navigation and Animation in a Volume Visualization System

The VolVis system for volume visualization supports numerous visualization algorithms and methods within a consistent and well-organized framework. Navigation and Animation components have been incorporated into VolVis which allow interactive object manipulation and quick specification of complex animation sequences. Navigation is controlled by a variety of 2D and 3D input devices. VolVis includes a unified protocol for communicating with these input devices, allowing for input device independent development.