Incremental radiosity: an extension of progressive radiosity to an interactive image synthesis system

Abstract

Traditional radiosity methods can compute the illumination for a scene independent of the view position. However, if any part of the scene geometry is changed, the radiosity process will need to be repeated from scratch. Since the radiosity methods are generally expensive computationally, the traditional methods do not lend themselves to interactive uses where the geometry is constantly changing. This paper presents a new radiosity algorithm to incrementally render scenes with changing geometry and surface attributes. In other words, the question to be asked is " What is the minimum recomputation I need to do if I turn off a light source, change the color of a surface, add or move an object? " Because a modeling change generally exhibits some coherence and affects only parts of an image, the proposed method may drastically reduce the rendering time and therefore allow interactive manipulation. In addition, since the method is conducted incrementally and view-independently, the rendering process can start before the modeling process is completed. The traditional paradigm of modeling-then-rendering is changed to rendering-while-modeling . This approach not only gives the user better visual feedback but also effectively utilizes CPU time otherwise wasted in the modeling process.