Online Occlusion Culling

A computer application that renders a virtual environment, for example an architectural model for use in a walkthrough scenario, can suffer from low performance due to the complexity of the environment. Visibility algorithms are concerned with determining the part of the environment that is visible and therefore necessary to render while discarding the rest, thereby reducing the workload of the graphics hardware. One group of visibility algorithms is concerned with determining which objects are blocked from view by other objects; this is called occlusion culling. Occlusion culling can be applied to for example the interiors of buildings or the contents of containers. In this thesis, the general problem of visibility in three-dimensional scenes will be presented as well as algorithms that attempt to solve it, especially methods to perform occlusion culling and in particular algorithms that perform occlusion culling online, without significant precalculations. Among these, several algorithms that take advantage of a recently developed graphics hardware extension will be described in detail, implemented and their performance and complexity analyzed.