Real-time Rendering of Complex Photorealistic Landscapes Using Hybrid Level-of-Detail Approaches

Abstract

It still remains a challenge to realistically render outdoor scenes with interactive frame-rates since these scenes consist of a immense number of highly complex geometric models. A square kilometre of a forest incorporates millions of plants, hundreds of thousands of trees, and numerous small shrubs. Even the explicit storage of the plant positions is extremly challenging and must therefore be avoided. The vast amount of geometry can only be handled using efficient level-of-detail algorithms that approximate larger parts of the scenes by very simple elements.In this paper procedures are demonstrated by representing models and parts of the scene by dynamically changing sets of billboards. After a survey of existing literature in the next paragraphs we first present algorithms to optimally approximate plant models using billboards. Sect. 3 introduces methods to realistically illuminate these billboards, which is important for a realistic rendition of the scene and for a smooth transition from billboard approximation to the detailed geometry. The geometry is still needed for close-ups of the plants since billboard clouds do not completely avoid parallax errors and cannot represent the details of a geometry-based model. To allow the approximation of larger parts of the scene, square tiles in the background consisting of many plant models are represented by combined groups of billboards that can be displayed with a single rendercall per tile and not with a rendercall per position. Following the presentation and discussion of the results, we will outline our future works.