Volume Visualization in Projection-Based Virtual Environments: Interaction and Exploration Tools Design and Evaluation

Abstract

Examples of volume data include medical scanned data such as CT and MRI data, seismic survey data, and computational fluid dynamic (CFD) data, etc. To better understand volumetric datasets, people use computer hardware and software to manipulate the data and generate 2D projections for viewing; this process is called volume visualization. Much research on volume visualization has been focused on volume rendering (how to render larger sets of data faster with a higher level of realism) or transfer function generation (how to highlight the regions of interest). To help improve the efficiency and efficacy of volume visualization, this research proposed using two different approaches. The first approach is to integrate virtual reality environments (VEs) and human computer interaction (HCI) technologies in volume visualization applications. The second approach is to use various virtual tools that allow users to directly explore and manipulate the volume data in 3D space. A volume visualization system named VRVolVis (Virtual Reality Volumes Visualization System) has been designed and developed to implement these approaches. Many innovations have been integrated into this system, including a fast volume rendering engine, an intuitive HCI paradigm tailored for volume visualization in VEs, and 8 innovative geometric tools that can assist users to fully reveal the internal structure of volumetric datasets. The tools are the clipping plane widget, the data slab widget, the volume probing tool, the volume clipping tool, the regional enhancement tool, the virtual light, the volume eraser and restorer, and the shooting star tool. Two sets of experiments involving 33 participants were conducted, and the experimental results supported the assertion that volume visualization tasks would be performed significant better in VR viewing conditions than Stereo and Conventional conditions, and that using these geometric tools can significantly improve the efficiency and efficacy of the volume visualization process.