A Realtime Procedural Universe - Our Entry to the WS2004/05 Rendering Competition

Teaching Assistant : Natalia Slesareva

Florian Winter, 2024653

Sascha Simon, 2015529

Jan, 13th 2005

Figure 1. Realtime Procederal Universe

Our entry to the rendering competition WS2004/05 is a small and fully procedural universe calculated and rendered in real-time. The user can explore the procedural universe interactively by flying over and between planets. Every planet in the universe has a unique appearance and features its own shading and atmospheric effects, fractal landscapes and procedural colors and textures with adaptive level of detail. This document describes the techniques and algorithms used to build and render the virtual universe. It also describes the interactive user interface.

Table of Contents
1. Overview
2. Usage and Keybindings
3. The Terrain Architecture
3.1. The Basic ROAM Algorithm
3.2. Extensions to the ROAM Algorithm
3.3. Possible Improvements
4. Atmosphere Simulation
4.1. General Operation of the Atmospheric Shaders
4.2. Optical Path Length using Per-Vertex Raytracing
4.3. Integration of the Fog Density Distibution
4.4. Simulating Atmospheric Scattering
4.5. References
5. Fractal Landscape and Texture Generation
5.1. The Basis Function
5.2. Types of Fractals
5.3. Textures
5.4. Added Craters
6. Toon-Shading
References

1. Overview

Central to our realtime procedural universe is the terrain rendering architecture. Every planet is a displaced sphere which is rendered with adaptive level of detail using a clustered spherical ROAM diamond mesh. All other techniques used in our universe are in some way related to terrain. This includes shading of the terrain, procedural texture generation, fractal displacement maps, atmospheric shading and other effects to make the terrain of planets look interesting. In this section, we give a quick overview of the used tecnniques and algorithms. We also give an overview of the planets and moons in our universe and which techniques and effects can be observed where. In the sections that follow, we describe each of the used techniques in detail.

  1. Earth

    To create an earth-like planet, we combined nearly all the techniques we implemented in our framework. Earth has a realistic atmosphere, a multifractal landscape and a texture which simulates climate zones. The coastlines of earth require special handling by our terrain meshing algorithm to be rendered with appropriate detail. Even small islands that appear as less than a pixle from space, or are not visible at all, can be viewed at high detail in close-up.

  2. Moon

    This is our first moon. Although its landscape is only a simple fractal function, it features some moon-like effects such as craters. Unlike those of the other moon, these craters have not been added explicitly. They are a "natural" feature of the fractal function we used. This moon also uses a special shader which simulates the dust-covered surface of Earth's moon, which reflects light in all directions.

  3. Toon Moon

    A simple toon-shaded moon with an exaggerated fractal crater landscape.

  4. Cratered Moon

    A modification of our first moon. This one features craters that can be explicitly placed at arbitrary positions on the surface, whereas the simple fractal moon has random craters. Also the craters on this moon are parameterized, so it is easier to control their appearance, e.g. to make them look more like impact craters.

  5. Jupiter

    A simple gas-gian planet which serves as background for our other planets.

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