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.

Interactively manipulating the geometry of complex, globally illuminated scenes has to date proven an elusive goal. Previous attempts have failed to provide interactive updates of global illumination and have not been able to offer well-adapted algorithms controlling the frame rate. The need for such interactive updates of global illumination is becoming increasingly important as the field of application of radiosity algorithms widens. To address this need, we present a novel algorithm which provides interactive update rates of global illumination for complex scenes with moving objects. In the context of clustering for hierarchical radiosity, we introduce the idea of an implicit line-space hierarchy. This hierarchy is realized by augmenting the links between hierarchical elements (clusters or surfaces) with shafts, representing the set of lines passing through the two linked elements. We show how line-space traversal allows rapid identification of modified links, and simultaneous clean...

While large investments are made in sophisticated graphics hardware, most realistic rendering is still performed off-line using ray trace or radiosity systems. A coordinated use of hardware-provided bitplanes and rendering pipelines can, however, approximate ray trace quality illumination effects in a user-interactive environment, as well as provide the tools necessary for a user to declutter such a complex scene. A variety of common ray trace and radiosity illumination effects are presented using multi-pass rendering in a pipeline architecture. We provide recursive reflections through the use of secondary viewpoints, and present a method for using a homogeneous 2-D projective image mapping to extend this method for refractive transparent surfaces. This paper then introduces the Dual Z-buffer, or DZ-buffer, an evolutionary hardware extension which, along with current framebuffer functions such as stencil planes and accumulation buffers, provides the hardware platform to render non-refr...

We describe new tools for the interactive design of complex, time-dependent lighting in scenes with fixed geometry. The work is motivated by the difficulty in visualizing complicated lighting sequences during the design of large-scale theatrical productions.Fast interaction is achieved regardless of scene and lighting complexity, even when used in conjunction with costly rendering techniques such as radiosity and ray tracing. Time-variant lighting is simulated using linear combinations of static images, each depicting the scene under different lighting conditions. Multiple levels of accuracy facilitate interactive design by trading image quality for fast feedback in a controlled way. Coarse approximations are used in the preliminary design stage to allow for instantaneous feedback, then the sequence is progressively refined by computing basis solutions in order of increasing overall contribution. When changes to the design are required, existing global solutions are re-used to the grea...

A method of determining radiosity in an environment containing moving objects, is described. This method uses the hierarchical techniques of Hanrahan et al. to obtain a static solution. Hanrahan's techniques efficiently create a hierarchical meshing of the environments geometry, and create links from element to element based on the magnitude of the form-factor between the elements. These ideas extend naturally to a dynamic environment, as only three atomic editing operations are required to update a hierarchy when an object moves: a link can be moved up or down the hierarchy, or a link can be occluded. Our algorithm exploits these simple editing processes to maintain the hierarchy, and then uses an iterative technique to solve the resulting linear system. The approach is extremely efficient, requiring little work between frames. Keywords: Radiosity, Computer Graphics. 0.1 Introduction Diffuse interreflections are a source of various substantial effects in the radiance of scenes. Rep...

We present a framework for interactive lighting design based on linear re-rendering. The rendering operation is linear with respect to light sources, assuming a fixed scene and camera geometry. This linearity means that a scene may be interactively rerendered via linear combination of a set of basis images, each rendered under a particular basis light.We focus on choosing and designing a suitable set of basis lights. We provide examples of bases that allow 1) interactive adjustment of a spotlight direction, 2) interactive adjustment of the position of an area light, and 3) a combination in whichlight sources are adjusted in both position and direction. We discuss a method for reducing the size of the basis using principal components analysis in the image domain.

Global illumination algorithms are regarded as computationally intensive. This cost is a practical problem when producing animations or when interactions with complex models are required. Several algorithms have been proposed to address this issue. Roughly, two families of methods can be distinguished. The first one aims at providing interactive feedback for lighting design applications. The second one gives higher priority to the quality of results, and therefore relies on offline computations. Recently, impressive advances have been made in both categories. In this report, we present a survey and classification of the most up-to-date of these methods. ACM CSS: I.3.7 Computer Graphics—Three-Dimensional Graphics and Realism 1.

The radiosity method became a very important tool in order to enable photorealistic rendering in virtual reality systems. Based on the geometric description of a scene, the view-independent illumination is computed in a preprocess and colors are assigned to each patch vertex. These virtual environments look very impressive, but any interaction with the scene geometry or its materials results in a time expensive recalculation of the radiosity simulation. This leads to the common phrase: Radiosity scenes are like museums, you may look around, but do not touch anything! In this paper, a new algorithm is presented to overcome this problem. The algorithm is based on the fact that most of the information needed for the radiosity repropagation after any scene modification was already computed during the radiosity preprocess. Therefore, the radiosity method is extended by storing shadow- and form-factor-information in an efficient data structure, the so-called shadow-form-factor-list (SFFL)....

A whole variety of different techniques for simulating global illumination in virtual environments have been developed over recent years. Each technique, including Radiosity, Monte-Carlo ray- or photon tracing, and directional-dependent Radiance computations, is best suited for simulating only some special case environments. None of these techniques is currently able to efficiently simulate all important lighting effects in non-trivial scenes. In this paper, we describe a new approach for efficiently combining different global illumination algorithms to yield a composite lighting simulation: Lighting Networks. Lighting Networks can exploit the advantages of each algorithm and can combine them in such a way as to simulate lighting effects that could only be computed at great costs by any single algorithm. Furthermore, this approach allows a user to configure the Lighting Network to compute only specific lighting effects that are important for a given task, while avoiding a costly simulation of the full global illumination in a scene. We show how the light paths computed by a Lighting Network can be described using regular expressions. This mapping allows us to analyze the composite lighting simulation and ensure completeness and redundant-free computations. Several examples demonstrate the advantages and unique lighting effects that can be obtained using this technique. 1

We describe a new framework for efficiently computing and storing global illumination effects for complex, animated environments. The new framework allows the rapid generation of sequences representing any arbitrary path in a "view space" within an environment in which both the viewer and objects move. The global illumination is stored as time sequences of range-images at base locations that span the view space. We present algorithms for determining locations for these base images, and the time steps required to adequately capture the effects of object motion. We also present algorithms for computing the global illumination in the base images that exploit spatial and temporal coherence by considering direct and indirect illumination separately. We discuss an initial implementation using the new framework. Results and analysis of our implementation demonstrate the effectiveness of the individual phases of the approach; we conclude with an application of the complete framework t...