Expressive Animated Character Sequences Using Knowledge-Based Painterly Rendering

We propose a technique to enhance emotional expressiveness in games and animations. Artists have used colors and painting techniques to convey emotions in their paintings for many years. Moreover, researchers have found that colors and line properties affect users' emotions. We propose using painterly rendering for character sequences in games and animations with a knowledge-based approach. This technique is especially useful for parametric facial sequences. We introduce two parametric authoring tools for animation and painterly rendering and a method to integrate them into a knowledge-based painterly rendering system. Furthermore, we present the results of a preliminary study on using this technique for facial expressions in still images. The results of the study show the effect of different color palettes on the intensity perceived for an emotion by users. The proposed technique can provide the animator with a depiction tool to enhance the emotional content of a character sequence in games and animations. 1. Introduction The expressiveness of character-based animations heavily relies on their success in conveying emotions to their viewers. In order to achieve high levels of expressiveness, today's game character sequences not only rely on the animation techniques, but also on other elements such as lighting and scene composition. The latter not only enhances the emotional content of the scene, but also draws attention to the specific regions designed for conveying the message. In a similar way, painters use color, various brush strokes, and painting techniques to emphasize certain features of a scene while leaving out unnecessary details. Edward Munch and Vincent Van Gogh are two exemplary artists that used colors to depict emotions in their work [1]. The use of texture for inducing mood is also evident in different brush stroke styles used by artists [2]. The emotional effects of art and paintings on users point to the importance of visual style on users' perception and emotional responses. Some past psychological studies demonstrated that there are links between rendering style and one's perception and feelings about a rendered object [3–5]. Furthermore, some other studies investigated people's association between colors and emotion [1, 5, 6]. Painterly rendering, a subset of Nonphotorealistic Rendering (NPR) simulates the work of illustrators and portrait artists and is commonly reported as an expressive style [7–9]. We propose using the expressive style of painterly rendering to enhance the emotional content of facial character sequences in games