Electric-field-based Transfer Functions for Volume Visualization

Abstract

Transfer functions play a crucial role in direct volume rendering. The intensity and gradient magnitude (IGM) space is one of the most commonly used transfer function spaces, in which boundaries between different materials appear as arches. However, there are often overlapping regions of adjacent arches in the space, which makes it difficult for users to design good transfer functions for exploring and visualizing tissues of interest. To deal with this problem, the present study proposes a transfer function space based on electric field theory. For each voxel, the volume charge density and electric force magnitude in its local neighborhood are calculated. Then, the two properties are used to create the transfer function space. Compared with the IGM space, the proposed space significantly reduces the number of overlapping regions of adjacent arches and produces more compact arches. Thus, users can design appropriate transfer functions for tissues of interest and obtain meaningful visualizations. Results for various datasets are used to illustrate the effectiveness of the proposed method.