Lighting has long been recognized as a crucial element in enhancing the appeal and emotional depth of characters across different media formats. This study investigates the impact of well-established portrait lighting designs on the perception of realistic digital human characters. We provide insight into how real-world lighting styles can be used to enhance the perceived appeal, trustworthiness, and emotional authenticity of digital human characters while minimizing the sense of eeriness. The findings of this study are expected to contribute to the understanding of how lighting influences the perception of digital characters and inform the development of more engaging virtual experiences in various domains.

The demand for cartoon animation content is on the rise, driven largely by social media, video conferencing and virtual reality. New content creation tools and the availability of open-source game engines allow characters to be animated by even novice creators (e.g., Loomie and Pinscreen for creating characters, Hyprface and MotionX for facial motion capture, etc,). However, lighting of animated characters is a skilled art-form, and there is a lack of guidelines for lighting characters expressing emotion in an appealing manner.

Lighting has been used to enhance emotion and appeal of characters for centuries, from paintings in the Renaissance to the modern-day digital arts. In VFX and animation studios, lighting is considered as important as modelling, shading, or rigging. Most existing work focuses on either empirical best-practice created by artists of the centuries or on lighting perception with basic shapes. In contrast, our work focuses on the effect of lighting on emotional characters. Our study presents an extensive set of novel perceptual experiments designed to investigate the effects of brightness levels (key light brightness) and the proportion of light intensity illuminating the two sides of a character’s face (key-to-fill ratio). We are particularly interested in the effect of lighting on the recognition of emotion, emotion intensity, and the overall appeal, as these are crucial factors for audience engagement. Our results have implications for artists and developers wishing to increase the appeal and emotional expression of their characters, ranging from cartoon to realistic styles. Our key finding is that lighting can be used to effectively alter the intensity of emotion of a character and that brighter conditions increased appeal across all of our experiments.

Lighting is a commonly used tool to manipulate the appearance of virtual characters in a range of applications. However, there are few studies which systematically examine the effect of lighting changes on complex dynamic stimuli. Our study presents several perceptual experiments, designed to investigate the ability of participants to discriminate lighting levels and the ratio of light intensity projected on the two sides of a cartoon character’s face (key-to-fill ratio) in portrait lighting design. We used a standard psychophysical method for measuring discrimination, typical in low-level perceptual studies but not frequently considered for evaluating complex stimuli. We found that people can easily differentiate lighting intensities, and distinguish between shadow strength and scene brightness under bright conditions but not under dark conditions. We provide a model of the results, and empirically validate the predictions of the model. We discuss the practical implications of our results and how they can be exploited to make the process of portrait lighting for CG cartoon characters more consistent, such as a tool for manipulating shadow while maintaining the level of perceived brightness.

The design of lighting in Computer Graphics is directly derived from cinematography, and many digital artists follow the conventional wisdom on how lighting is set up to convey drama, appeal, or emotion. In this paper, we are interested in investigating the most commonly used lighting techniques to more formally determine their effect on our perception of animated virtual characters. Firstly, we commissioned a professional animator to create a sequence of dramatic emotional sentences for a typical CG cartoon character. Then, we rendered that character using a range of lighting directions, intensities, and shading techniques. Participants of our experiment rated the emotion, the intensity of the performance, and the appeal of the character. Our results provide new insights into how animated virtual characters are perceived, when viewed under different lighting conditions.