Hairy Slices: Evaluating the Perceptual Effectiveness of Cutting Plane Glyphs for 3D Vector Fields

Abstract

Three-dimensional vector fields are common datasets throughout the sciences. Visualizing these fields is inherently difficult due to issues such as visual clutter and self-occlusion. Cutting planes are often used to overcome these issues by presenting more manageable slices of data. The existing literature provides many techniques for visualizing the flow through these cutting planes; however, there is a lack of empirical studies focused on the underlying perceptual cues that make popular techniques successful. This paper presents a quantitative human factors study that evaluates static monoscopic depth and orientation cues in the context of cutting plane glyph designs for exploring and analyzing 3D flow fields. The goal of the study was to ascertain the relative effectiveness of various techniques for portraying the direction of flow through a cutting plane at a given point, and to identify the visual cues and combinations of cues involved, and how they contribute to accurate performance. It was found that increasing the dimensionality of line-based glyphs into tubular structures enhances their ability to convey orientation through shading, and that increasing their diameter intensifies this effect. These tube-based glyphs were also less sensitive to visual clutter issues at higher densities. Adding shadows to lines was also found to increase perception of flow direction. Implications of the experimental results are discussed and extrapolated into a number of guidelines for designing more perceptually effective glyphs for 3D vector field visualizations.

Hairy Slices II: Depth Cues for Visualizing 3D Streamlines Through Cutting Planes

“…Pilot testing indicated that the two streamlet conditions would benefit from additional seeds, and the seeding density was increased to 40×40 (a four‐times increase), as can be seen in Figures 2a and 2b. This increase of seed density is supported by the results of our prior work [SBW16], which found that thin glyph geometries could be successfully seeded at higher densities than thicker geometries without a reduction in perceptual performance.…”

“…In general, the method and experimental design follows those described in the previous paper [SBW16], with some improvements.…”

“…However, when target vectors are nearly parallel with the viewing direction, even small overall angular errors can generate very big projection errors. See the previous paper [SBW16] for an in‐depth discussion of this challenge and our solution, which is to apply a weighting factor, so that parallel target vectors (which come straight at or away from viewers) receive the lowest weight, while vectors orthogonal to the viewing direction (i.e. along the cutting plane) are assigned the highest weight.…”

“…A thorough background on many of these cues and an exhaustive discussion of related works can be found in our previous report [SBW16]. To provide some of that background, it is summarized below.…”

“…[LWSH04]) and this can be done using 3D glyphs. Because a dense set of glyphs passing through a plane can resemble fur, we call the method "Hairy Slices" [SBW16].…”