Automatic expressive lighting for interactive scenes
Ian Douglas Horswill, Magy Seif El-Nasr · 2003
Advances in computer graphics have led to the development of interactive entertainment applications with complex 3D graphical environments. Lighting is becoming increasingly important in such applications not only because of its role in illumination, but also because of its utility in directing the viewer's gaze to important areas and evoking moods. However, lighting design is a complex process, and is especially problematic for interactive applications. Rendering time for such applications is linear in the number of lights used, thus restricting the number of lights used in real-time rendering engines to 8 or fewer; yet current practice in the animation industry is to use 32 lights or more per scene. Moreover, the scene's spatial configuration, mood, dramatic intensity, and the relative importance of different characters, all change unpredictably in real time, necessitating continual redesign as the characters and camera move. Current systems, however, use fixed, manually designed lighting. This manual design is labor intensive and leads to partially invisible characters, unmotivated or distracting color changes, and frustration for the player/audience. In this dissertation, I present a new approach to lighting design for interactive scenes. I will describe this approach using the Expressive Lighting Engine (ELE) that I have developed. ELE uses non-linear constraint optimization to automatically and unobtrusively adjust lighting in real-time, utilizing traditional cinematic and theatrical lighting design theory. This approach accommodates variations in spatial and dramatic configurations that occur during interactive scenes. ELE also allows artists to author lighting changes and override its decisions. ELE accommodates artistic desires, but also maintains style and visual continuity within an interactive scene.