Perceptual Effects of Inconsistency in Human Animations

Abstract

The individual shape of the human body, including the geometry of its articulated structure and the distribution of weight over that structure, influences the kinematics of a person's movements. How sensitive is the visual system to inconsistencies between shape and motion introduced by retargeting motion from one person onto the shape of another? We used optical motion capture to record five pairs of male performers with large differences in body weight, while they pushed, lifted, and threw objects. From these data, we estimated both the kinematics of the actions as well as the performer's individual body shape. To obtain consistent and inconsistent stimuli, we created animated avatars by combining the shape and motion estimates from either a single performer or from different performers. Using these stimuli we conducted three experiments in an immersive virtual reality environment. First, a group of participants detected which of two stimuli was inconsistent. Performance was very low, and results were only marginally significant. Next, a second group of participants rated perceived attractiveness, eeriness, and humanness of consistent and inconsistent stimuli, but these judgements of animation characteristics were not affected by consistency of the stimuli. Finally, a third group of participants rated properties of the objects rather than of the performers. Here, we found strong influences of shape-motion inconsistency on perceived weight and thrown distance of objects. This suggests that the visual system relies on its knowledge of shape and motion and that these components are assimilated into an altered perception of the action outcome. We propose that the visual system attempts to resist inconsistent interpretations of human animations. Actions involving object manipulations present an opportunity for the visual system to reinterpret the introduced inconsistencies as a change in the dynamics of an object rather than as an unexpected combination of body shape and body motion.

A Survey on Realistic Virtual Human Animations: Definitions, Features and Evaluations

“…Shape‐motion inconsistency affected the perceived weight and thrown distance of objects, suggesting that the visual system assimilates shape and motion information to alter the perception of action outcomes. The effect of inconsistencies however varied depending on the action observed, with viewers' detection of inconsistencies between shape and motion being typically close to chance level for transitive actions (i.e., actions involving an object) [KMH*19,RSM*23], but above chance level for walking animations [RSM*23]. Overall, these results suggest that detection rate is typically low, despite slight differences between male and female animations.…”

“…However, such characteristics could be associated with specific attention mechanisms to the resulting animation that might affect participants' answers and behaviours [ZKM18]. We also want to point out that the majority of the user studies, usually conducted in laboratories, recruited young and healthy adults, i.e., typically students (e.g., age was between 18 and 26 in the work of Kenny et al [KMH*19]). One can then question the generalisation of the results to more diverse population, which is seldom considered in our community.…”

“…While not evaluating realism, their results show a significant link between internal consistency and attractiveness, and is therefore potential relevant for creating realistic VH motions. This question was further explored by Kenny et al [KMH*19], who studied how the dense representation of a VH (e.g., geometry of the articulated structure and distribution of skinning weights over that structure) could influence the kinematics of his/her movements. Particularly, they examined the effect of internal inconsistencies introduced by retargeting motion from one person onto the shape of another.…”

“…Several authors [KHT16, KMH*19, RSM*23] were interested in studying the consistency between the shape and the motion of VH animation. For instance, Kluver et al [KHT16] studied the effect of internal consistency, which refers to the coherence or harmony between different traits or features within a stimulus.…”

Working Memory Capacity of Biological Motion’s Basic Unit: Decomposing Biological Motion From the Perspective of Systematic Anatomy

“…Here we planned to explore whether the BM WMC remain unchanged regardless of the difficulties inherent in BMs, and if not, what underlying anatomical factors or others might have effects through the following three experiments, and hoped to uncover some approaches to partially overcome the above limitations. Using computer-generated motion animations technique, a technology that has been used several times ( Wood, 2007 , 2008 , 2010 ; Goldberg et al, 2015 ; Kenny et al, 2019 ; Kurz et al, 2020 ), by which we can strictly control concerned variables and remain irrelevant ones unchanged, thus enabled us develop more BMs with a low extend of conceptualization and then corroborate some hypothesis. First, we hypothesized that the difficulties inherent in the BMs bear some resemblance to each other but is not identical.…”