Shadows are essential to realistic and visually appealing images, but they are di cult to compute in most display environments. This survey will characterize the various types of shadows, describe most existing shadow algorithms, and for each one discuss their complexities, their advantages and their shortcomings. The types of shadows examined are hard shadows, soft shadows, shadows of transparent objects, and shadows for complex modeling primitives. For each type, we examine shadow algorithms within various rendering techniques. The goal of the survey is to provide readers with enough background and insight on the various methods to allow themtochoose the algorithm best suited to their needs. It is also hoped that our analysis will help identify the areas that need more research, and point to possible solutions.

This thesis presents a volumetric representation for the global illumination within a space based on the radiometric quantity irradiance. We call this representation the irradiance volume. Although irradiance is traditionally computed only for surfaces, its de nition can be naturally extended to all points and directions in space. The irradiance volume supports the reconstruction of believable approximations to the illumination in situations that overwhelm traditional global illumination algorithms. Atheoretical basis for the irradiance volume is discussed and the methods and issues involved with building the volume are described. The irradiance volume method is tested within several situations in which the use of traditional global illumination methods is impractical, and is shown to provide good performance.

Realistic image generation is presented in a theoretical formulation that builds from previous work on the rendering equation. Previous and new solution techniques for the global illumination are discussed in the context of this formulation. The basic

We define the antiumbra and the antipenumbra of aconvex area light source shining through a sequence of convex areal holes in three dimensions. The antiumbra is the volume from which all points on the light source can be seen. The antipenumbra is the volume from which some, but not all, of the light source can be seen. We show that the antipenumbra is, in general, a disconnected set bounded by portions of quadric surfaces, and describe an implemented O(n 2 ) time algorithm that computes this boundary, where n is the total number of edges comprising the light source and holes. The antipenumbra computation is motivated by a visibility scheme in which we wish to determine the volume visible to an observer looking through a sequenceof transparent convex holes, or portals, connecting adjacent cells in a spatial subdivision. Knowledge of the antipenumbra should also prove useful for rendering shadowed objects. Finally, we have extended the algorithm to compute the planar and quadratic su...

this paper, we present a system that exploits object-space, rayspace, image-space and temporal coherence to accelerate ray tracing. Our system uses per-surface interpolants to approximate radiance, while conservatively bounding error. The techniques we introduce in this paper should enhance both interactive and batch ray tracers.

This paper presents a method for designing the illumination in an environment using optimization techniques applied to a radiosity based image synthesis system. An optimization of lighting parameters is performed based on user specified constraints and objectives for the illumination of the environment. The system solves for the "best" possible settings for: light source emissivities, element reflectivities, and spot light directionality parameters so that the design goals, suchastominimize energy or to give the the room an impression of privacy, are met. The system absorbs much of the burden for searching the design space allowing the user to focus on the goals of the illumination design rather than the intricate details of a complete lighting specification. A software implementation is described and some results of using the system are reported.

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this paper weintroduce two solutions for rendering surfaces illuminated by linear light sources. The #rst is an analytic solution that is exact though a little expensive. The second allows us to compute the e#ects of these light sources inexpensively yet avoiding the sampling problems of standard approaches. When extending the light source to a line, the shadows have to be handled di#erently in order to capture the variation of intensity within the shadow region. An algorithm to compute the umbra and penumbra regions of shadows is presented. This algorithm allows the objects in a scene to not be limited to polygons only.We #rst review shading and the various light sources currently in use in computer graphics. The two solutions are then derived and the shadowing algorithm is introduced. Finally, results are presented and discussed.

The time complexity of Monte Carlo radiosity is discussed, and a proof is given that the expected number of rays required to produce a statistical radiosity solution below a specified variance for N zones is O(N ). A satisfactory solution is defined to be one in which the variance of radiance estimates for each zone is below a predefined threshold. The proof assumes that the radiance is bounded, and the area ratio of the largest to smallest zone is bounded. 1 Introduction In a radiosity (zonal) program, the surfaces in the environment are broken into N zones, z i , and the radiance, L i , of each zone is calculated [6, 7]. In the most straightforward radiosity method, all N 2 relationships (form-factors) are explicitly calculated, so the time complexity of the program is at least O(N 2 ). One of the first schemes to lower the radiosity calculation time was to group the N zones into p patches, and transfer power from patches to zones (elements) [4]. Still, the computation time wil...

Classical ray-tracing algorithms compute radiance returning to the eye along one or more sample rays through each pixel of an image. The output of a ray-tracing algorithm, although potentially photorealistic, is a two-dimensional quantity -- an image array of radiance values -- and is not directly useful from any viewpoint other than the one for which it was computed. This paper