A method is described which models the interaction of light between diffusely reflecting surfaces. Current light reflection models used in computer graphics do not account for the object-to-object reflection between diffuse surfaces, and thus incorrectly compute the global illumination effects. The new procedure, based on methods used in thermal engineering, includes the effects of diffuse light sources of finite area, as well as the "color-bleedlng " effects which are caused by the diffuse reflections. A simple environment is used to illustrate these simulated effects and is presented with photographs of a physical model. The procedure is applicable to environments composed of ideal diffuse reflectors and can account for direct illumination from a variety of light sources. The resultant surface intensities are independent of observer position, and thus environments can be preprocessed for dynamic sequences.

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.

We introduce a new concept for accelerating realistic image synthesis algorithms. At the core of this procedure is a novel physical error metric that correctly predicts the perceptual threshold for detecting artifacts in scene features. Built into this metric is a computational model of the human visual system's loss of sensitivity at high background illumination levels, high spatial frequencies, and high contrast levels (visual masking). An important feature of our model is that it handles the luminance-dependent processing and spatiallydependent processing independently. This allows us to precompute the expensive spatially-dependent component, making our model extremely efficient. We illustrate the utility of our procedure with global illumination algorithms used for realistic image synthesis. The expense of global illumination computations is many orders of magnitude higher than the expense of direct illumination computations and can greatly benefit by applying our perceptually bas...

We examine various simple algorithms that exploit homogeneity and accumulated opacity for tracing rays through shaded volumes. Most of these methods have error criteria which allow them to trade quality for speed. The time vs. quality tradeoff for these adaptive methods is compared to fixed step multiresolution methods. These methods are also useful for general light transport in volumes. 1 Introduction We are interested in speeding volume ray tracing computations. We concentrate on the one dimensional problem of tracing a single ray, or computing the intensity at a point from a single direction. In addition to being the kernel of a simple volume ray tracer, this computation can be used to generate shadow volumes and as an element in more general light transport problems. Our data structures will be view independent to speed the production of animations of preshaded volumes and interactive viewing. In [11] Levoy introduced two key concepts which we will be expanding on: presence accel...

This paper describes algorithmic procedures that have been implemented to reduce the computational expense of producing ray-traced images. The selection of bounding volumes is examined to reduce the computational cost of the ray-intersection test. The use of object coherence, which relies on a hierarchical description of the environment, is then presented. Finally, since the building of the ray-intersection trees is such a large portion of the computation, a method using image coherence is described. This visible-surface preprocessing method, which is dependent upon the creation of an "item buffer, " takes advantage of a priori image information. Examples that indicate the efficiency of these techniques for a variety of representative environments are presented.

A new approach to ray tracing is introduced. The definition of a "ray" is extended into a cone by including information on the spread angle and the virtual origin. The advan-tages of this approach, which tries to model light propagation with more fidelity, include a better method of anti-aliasing, a way of calculating fuzzy shadows and dull reflections, a method of calculating the correct level of detail in a procedural model and texture map, and finally, a procedure for faster intersection calculation.

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

A method is presented that takes as an input a 2D microfacet orientation distribution and produces a 4D bidirectional reflectance distribution function (BRDF). This method differs from previous microfacet-based BRDF models in that it uses a simple shadowing term which allows it to handle very general microfacet distributions while maintaining reciprocity and energy conservation. The generator is shown on a variety of material types.

INTRODUCTION Global illumination is the physically accurate calculation of lighting in an environment. It is computationally expensive for static environments and even more so for dynamic environments. Not only are many images required for an animation, but the calculation involved increases with the presence of moving objects. In static environments, global illumination algorithms can precompute a lighting solution and reuse it whenever the viewpoint changes, but in dynamic environments, any moving object or light potentially affects the illumination of every other object in a scene. To guarantee accuracy, the algorithm has to recompute the entire lighting solution for each frame. This paper describes a perceptually-based technique that can dramatically reduce this computational load. The technique may also be used in image based rendering, geometry level of detail selection, realistic image synthesis, video telephony and video compression. Perceptually-based rendering operat