Evaluating the plausibility of edited throwing animations

Animation budget constraints during the development of a game often call for the use of a limited set of generic motions. Editing operations are thus generally required to animate virtual characters with a sufficient level of variety. Evaluating the perceptual plausibility of edited animations can therefore contribute greatly towards producing visually plausible animations. In this paper we study observers' sensitivity to manipulations of overarm and underarm biological throwing animations. In our first experiment, we used Dynamic Time Warping to edit the biological throwing motions, and modified the release velocity of the ball accordingly. We found that observers are more tolerant to speeding up of the original throwing motion than to slowing down, and that slowed down underarm throws are perceived as particularly unnatural. In our second experiment, we modified separately horizontal and vertical components of the release velocity of the ball, while leaving the motion of the thrower unchanged. We found that observers are more sensitive to manipulations of the horizontal component in overarm throws, and of the vertical component in underarm throws. As in the first experiment, we found that observers are most disturbed by decreases in the velocity of the ball in underarm throws. Our results provide valuable insights for developers of games and VR applications by specifying thresholds for the perceptual plausibility of throwing manipulations.