[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: The most straightforward image synthesis algorithm is to follow photon-like particles from luminaires through the environment. These particles scatter or are absorbed when they interact with a surface or a volume. They contribute to the image if and when they strike a sensor. Such an algorithm implicitly solves the light trans- port equation. Alternatively, adjoint photons can be traced from the sensor to the luminaires to produce the same image. This "ad- joint photon" tracing algorithm is described, and its strengths and weaknesses are discussed, as well as details needed to make adjoint photon tracing practical.
Proceedings of the Graphics Interface 2006 Conference, June 7-9, 2006, Quebec, Canada; 01/2006
[show abstract][hide abstract] ABSTRACT: We present an interactive system for placing emphasis in stylized renderings of 3D models. The artist chooses a camera position, an area of interest, and a rendering style for the scene. The system then automatically renders the scene with emphasis in the area of interest, an effect we call "stylized focus." Stylized focus draws the viewer's gaze to the emphasized area, through local variations in shading effects such as color saturation and contrast as well as line qualities such as texture and density. We introduce a novel algorithm for local control of line density that exhibits a degree of temporal coherence suitable for animation. Animating the area of emphasis produces an effect we call the "stylized focus pull." Finally, an eye-tracking experiment verifies that the emphasis does indeed draw the viewer's gaze to the area of interest.
Proceedings of the Eurographics Symposium on Rendering Techniques, Nicosia, Cyprus, 2006; 01/2006
[show abstract][hide abstract] ABSTRACT: The computational bottleneck in a ray tracer using bounding volume hierarchies is often the ray intersection routine with axis-aligned bounding boxes. We describe a version of this routine that uses IEEE numerical properties to ensure that those tests are both robust and efficient. Sample source code is available online.
[show abstract][hide abstract] ABSTRACT: Simple tone reproduction methods, such as the Reinhard global photographic tone-mapping operator, are popular methods for mapping high-dynamic range images to a low-dynamic range display. However, these methods deal mainly with how luminance is mapped; much less attention has been paid to how a full RGB color is produced. We introduce a simple method, inspired by traditional photography's use of polarizers to manage color, to map RGB colors when using global photographic operators for luminance. This method allows the user to trade off luminance for colorfulness, avoids unpredictable hue shifts and desaturation of the image, and guarantees that results lie in the RGB color cube without clamping.