Facial Animation Strategies for Improved Emotional Expression in Virtual Reality

The portrayal of emotions by virtual characters is crucial in virtual reality (VR) communication. Effective communication in VR relies on a shared understanding, which is significantly enhanced when virtual characters authentically express emotions that align with their spoken words. While human emotions are often conveyed through facial expressions, existing facial animation techniques have mainly focused on lip-syncing and head movements to improve naturalness. This study investigates the influence of various factors in facial animation on the emotional representation of virtual characters. We conduct a comparative and analytical study using an audio-visual database, examining the impact of different animation factors. To this end, we utilize a total of 24 voice samples, representing 12 different speakers, with each emotional voice segment lasting approximately 4-5 s. Using these samples, we design six perceptual experiments to investigate the impact of facial cues-including facial expression, lip movement, head motion, and overall appearance-on the expression of emotions by virtual characters. Additionally, we engaged 20 participants to evaluate and select appropriate combinations of facial expressions, lip movements, head motions, and appearances that align with the given emotion and its intensity. Our findings indicate that emotional representation in virtual characters is closely linked to facial expressions, head movements, and overall appearance. Conversely, lip-syncing, which has been a primary focus in prior studies, seems less critical for conveying emotions, as its accuracy is difficult to perceive with the naked eye. The results of our study can significantly benefit the VR community by aiding in the development of virtual characters capable of expressing a diverse range of emotions.