Donald S. Fussell

Uniformly Sampled Light Fields

Image-based or light field rendering has received much recent attention as an alternative to traditional geometric methods for modeling and rendering complex objects. A light field represents the radiance flowing through all the points in a scene in all possible directions. We explore two new techniques for efficiently acquiring, storing, and reconstructing light fields in a (nearly) uniform fashion. Both techniques sample the light field by sampling the set of lines that intersect a sphere tightly fit around a given object. Our first approach relies on uniformly subdividing the sphere and representing this subdivision in a compact data structure which allows efficient mapping of image pixels or rays to sphere points and then to subdivision elements. We sample a light field by joining pairs of subdivision elements and store the resulting samples in a multi-resolution, highly compressed fashion that allows efficient rendering. Our second method allows a uniform sampling of all five dimensions of the light field, using hierarchical subdivision for directional space and uniform grid sampling for positional space. Light field models are acquired using parallel projections along a set of uniform directions. Depth information can also be stored for high-quality image rendering. The system can provide bounds on key sources of error in the representation and can be generalized to arbitrary scenes comprising multiple complex objects.

Adaptive mesh generation for global diffuse illumination

Rapid developments in the design of algorithms for rendering globally illuminated scenes have taken place in the past five years. Net energy methods such as the hemicube and other radiosity algorithms have become very effective at computing the energy balance for scenes containing diffusely reflecting objects. Such methods first break up a scene description into a relatively large number of elements, or possibly several levels of elements. Energy transfers among these elements are then determined using a variety of means. While much progress has been made in the design of energy transfer algorithms, little or no attention has been paid to the proper generation of the mesh of surface elements. This paper presents a technique for adaptively creating a mesh of surface elements as the energy transfers are computed. The method allows large numbers of small elements to be placed at parts of the scene where the most active energy transfers occur without requiring that other parts of the scene be needlessly subdivided to the same degree. As a result, the computational effort in the energy transfer computations can be concentrated where it has the most effect.

Applying space subdivision techniques to volume rendering

The authors present a ray-tracing algorithm for volume rendering designed to work efficiently when the data of interest is distributed sparsely through the volume. A simple preprocessing step identifies the voxels representing features of interest. Frequently this set of voxels, arbitrarily distributed in three-dimensional space, is a small fraction of the original voxel grid. A median-cut space partitioning scheme, combined with bounding volumes to prune void spaces in the resulting search structure, is used to store the voxels of interest in a k-d tree. The k-d tree is used as a data structure. The tree is then efficiently ray-traced to render the voxel data. The k-d tree is view independent, and can be used for animation sequences involving changes in positions of the viewer or positions of lights. This search structure has been applied to render voxel data from MRI, CAT scan, and electron density distributions.<<ETX>>

Finding triconnected components by local replacement

A parallel algorithm for finding triconnected components on a CRCW PRAM is presented. The time complexity of the algorithm is

Probabilistic verification of Boolean functions

O(\log n)

Probabilistic design verification

, and the processor-time product is

Illumination networks: fast realistic rendering with general reflectance functions

O((m + n)\log \log n)

Probabilistic diagnosis of multiprocessor systems with arbitrary connectivity

, where n is the number of vertices and m is the number of edges of the input graph. The algorithm, like other parallel algorithms for this problem, is based on open ear decomposition, but it uses a new technique, local replacement, to improve the complexity. Only the need to use the subroutines for connected components and integer sorting, for which no optimal parallel algorithm that runs in

Dynamic Ray Scheduling to Improve Ray Coherence and Bandwidth Utilization

O(\log n)

Built-in testing of integrated circuit wafers

time is known, prevents the algorithm from achieving optimality.