Adaptive coherent hierarchical culling algorithm for UTM car driving simulator

Abstract

Driving simulator is a virtual reality tool that emulates actual driving environment. In a virtual world, feedback between the user and the application is a very critical aspect to be considered. Fundamentally, the drop of frame rates that influences feedback can cause control delay and disruption of user interactivity. To maintain human and computer interactivity, the best possible quality of rendering graphics would have to be within 60 frames per second. To achieve this quality, good selection of Visibility Culling (VC) algorithms are needed one of which is the Online Occlusion Culling (OOC) algorithm. The OOC requires no pre-processing and is suitable for dynamic scenes. The characteristic of the 3D dynamic scene is one of the main factors to efficiently integrate OOC into an existing driving simulator system. Hence, this research proposed an adaptive algorithm for Coherent Hierarchical Culling (CHC) algorithm derived from OOC to manage complex and dynamic objects in a dynamic driving simulation scene. The CHC requires a two-level process: preprocessing and online processing which are implemented to manage the occlusion queries. The proposed adaptive algorithm aims at improving CHC efficiency by manipulating two parameters which are the car movement speed and the visibility threshold. An experiment was conducted using car driving simulator engine tested on winding and hilly road, and an open straight road. The experiment showed that the speed of the car influenced the number of objects to be culled based on distance whereas the varying visibility thresholds reduced the popping artifacts problem of higher visibility threshold. Concurrently, both of them were able to reduce number of insignificant objects to be rendered. The results of the research showed that this adaptive algorithm improved the CHC rendering performance and maintained visual quality. This research has proven that the adaptive algorithm really improved upon the CHC for real-time simulator applications.