Is Photorealism Important for Perception of Expressive Virtual Humans in Virtual Reality?

In recent years, the quality of real-time rendering has reached new heights-realistic reflections, physically based materials, and photometric lighting are all becoming commonplace in modern game engines and even interactive virtual environments, such as virtual reality (VR). As the strive for realism continues, there is a need to investigate the effect of photorealism on users' perception, particularly for interactive, emotional scenarios in VR. In this article, we explored three main topics, where we predicted photorealism will make a difference: the illusion of being present with the virtual person and in an environment, altered emotional response toward the character, and a subtler response-comfort of being in close proximity to the character. We present a perceptual experiment, with an interactive expressive virtual character in VR, which was designed to induce particular social responses in people. Our participant pool was large (N = 797) and diverse in terms of demographics. We designed a between-group experiment, where each group saw either the realistic rendering or one of our stylized conditions (simple and sketch style), expressing one of three attitudes: Friendly, Unfriendly, or Sad. While the render style did not particularly effect the level of comfort with the character or increase the illusion of presence with it, our main finding shows that the photorealistic character changed the emotional responses of participants, compared to the stylized versions. We also found a preference for realism in VR, reflected in the affinity and higher place illusion in the scenario, rendered in the realistic render style.