Perceptual Adjustment of Eyeball Rotation and Pupil Size Jitter for Virtual Characters

Abstract

Eye motions constitute an important part of our daily face-to-face interactions. Even subtle details in the eyes’ motions give us clues about a person’s thoughts and emotions. Believable and natural animation of the eyes is therefore crucial when creating appealing virtual characters. In this article, we investigate the perceived naturalness of detailed eye motions, more specifically of jitter of the eyeball rotation and pupil diameter on three virtual characters with differing levels of realism. Participants watched stimuli with six scaling factors from 0 to 1 in increments of 0.2, varying eye rotation and pupil size jitter individually, and they had to indicate if they would like to increase or decrease the level of jitter to make the animation look more natural. Based on participants’ responses, we determine the scaling factors for noise attenuation perceived as most natural for each character when using motion-captured eye motions. We compute the corresponding average jitter amplitudes for the eyeball rotation and pupil size to serve as guidelines for other characters. We find that the amplitudes perceived as most natural depend on the character, with our character with a medium level of realism requiring the largest scaling factors.