Lighting with paint

Lighting is a fundamental aspect of computer cinematography that involves the placement and configuration of lights to establish mood and enhance storytelling. This process is labor intensive as artists repeatedly adjust the parameters of a large set of complex lights to achieve a desired effect. Typical lighting controls affect the final image indirectly, requiring a large number of trials to obtain a suitable result. We present an interactive system wherein an artist paints desired lighting effects directly into the scene, and the computer solves for parameters that achieve the desired look. The artist can paint color, light shape, shadows, highlights, and reflections using a suite of tools designed for painting light. Our system matches these effects using a nonlinear optimizer made robust by a combination of initial estimates, system design, and user-guided optimization. In contrast, previous work on painting light has not permitted the lights to move, allowing for linear optimization but preventing its use in computer cinematography. To demonstrate our approach we lit several scenes, mainly using a direct illumination renderer designed for computer animation, but also including two other rendering styles. We show that painting interfaces can quickly produce high quality lighting setups, easing the lighting artist's workflow.