1. Introduction

In many applications it is required to work with terrain models. We can divide these applications into several types. Main three types are geographical information systems (GIS), programs for simulating processes on the earth surface and below it and programs for image synthesis. Everyone of these applications has special requirements how a terrain model (its data structure) should look like. This depends on what terrain features we want to represent, what accuracy we need, how we obtain data and what are we going to do with the model. Next, we must consider memory complexity of the model and how difficult is to implement tools for its maintenance. In this article we will take an interest in data structure aimed at image synthesis software.

Image synthesis software does not need an exact model of the terrain. It means that some distances (heights) can be slightly different from exact ones. Nevertheless, topological properties of terrain must be stored correctly. Focus of image synthesis software does not lie in work with terrain, so the data structure should be simple and fast. It is often needed to represent complex terrain features like arches, overhangs etc. However, currently there is no data structure that can store such complex terrains. In the article we will discuss currently used data structures, give brief overview of methods for terrain generation and rendering and last we will derive data structure destined for storing complex terrains.

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