Using NPR to evaluate perceptual shape cues in dynamic environments

We present a psychophysical experiment to determine the effectiveness of perceptual shape cues for rigidly moving objects in an interactive, highly dynamic task. We use standard non-photorealistic (NPR) techniques to carefully separate and study shape cues common to many rendering systems. Our experiment is simple to implement, engaging and intuitive for participants, and sensitive enough to detect significant differences between individual shape cues. We demonstrate our experimental design with a user study. In that study, participants are shown 16 moving objects, 4 of which are designated targets, rendered in different shape-from-X styles. Participants select targets projected onto a touch-sensitive table. We find that simple Lambertian shading offers the best shape cue in our user study, followed by contours and, lastly, texturing. Further results indicate that multiple shape cues should be used with care, as these may not behave additively.