Level of detail techniques for real-time urban simulation

Abstract

Real-time urban simulation is an area of computer graphics with many applications, from city planning and emergency response to computer gaming. The task of creating and running a believable simulation of an urban area is not an easy one, especially when aiming towards commodity hardware. Much research into Level of Detail and Culling techniques has been performed to aid in the creation of virtual cities. We investigate some of these techniques as part of the creation of a large-scale real-time simulation of the city of Dublin, Ireland. This Virtual Dublin application aims to provide wide coverage at high detail, and be a believable representation of the real world. We evaluate the benefits that the various techniques provide for rendering a large urban environment with an extensive performance evaluation of the Virtual Dublin system. One of the main techniques used in the creation of the virtual city and other similar real-time applications is known as Impostor Rendering. This is the replacement of complex scene geometry that is far away from the user with simpler images that faithfully represent the original scene. These are typically updated and rendered according to purely geometric rules. We describe a series of Perceptual Psychophysical Experiments that test the thresholds at which impostor usage becomes noticeable to human participants. Finally we derive Perceptual Metrics based on the aforementioned experiments for impostor usage, with regards to those used in the virtual city. With such metrics, developers of real-time applications will have a guide to assist them in the creation of large urban simulations.