Non-Photorealistic Computer Graphics Library

Showing Shape with Texture – Two Directions are Better than One

Author(s): Sunghee Kim, Haleh Hagh-Shenas, Victoria Interrante.
Proceedings: 2002.
[BibTeX]

Abstract:
If we could design the perfect texture pattern to apply to any smooth surface in order to enable observers to more accurately perceive the surface’s shape, what would the characteristics of that texture pattern be? The answers to this question have important potential impact across a wide range of visualization applications, from molecular modeling to radiation therapy treatment planning, in which scientists need to attain an accurate, intuitive understanding of the shapes of complicated, smoothly curving surfaces in their data. Over the past several years, researchers in our lab have carried out a series of experiments intended to investigate the impact on shape perception of various characteristics of surface texture patterns. In this paper we report the results of our most recent study, in which we compare performance on a surface attitude probe adjustment task under three distinct conditions of principal direction pattern orientation and a control condition in which no texture was present. The three texture conditions were: a doubly-oriented texture in which approximately evenly-spaced lines follow both of the principal directions, a singly-oriented line texture which follows only the first principal direction, and a singly-oriented line integral convolution texture, from which information about texture compression in the direction of the texture flow may be indirectly accessible. Over a series of 200 trials (4 texture conditions x 10 surface/probe locations x 5 repeated measures), a total of five naïve participants were asked to adjust a circular probe, randomly located on an arbitrary doubly curved surface, so that its base appeared to lie in the displayed surface and its perpendicular extension appeared to be oriented in the direction of the surface normal. An analysis of the results showed that performance was best in the two-directional texture condition, closely followed by the line integral convolution condition. Performance was further decreased in the one-directional and no texture conditions (in that order). The paper is organized as follows. In section 1 we describe the motivation for our work. In section 2 we very briefly discuss previous and related work in the field of vision research, and briefly recap the findings of our first two experiments [9, 10] which focused on the effects of pattern anisotropy and the impact of texture orientation. In section 3 we describe our experimental methods, including a brief summary of the process of the stimuli preparation, and we present a detailed statistical analysis of our experimental results. In section 4 we discuss the implications of our findings, and in section 5 we outline plans for future work.