Project Specification

Procedural Generation of Clouds

Project aim

The aim of this project is to procedurally generate clouds and sunlight from actual weather data of Stockholm. The modeled clouds should be animated to drift along the sky according to the wind properties. The sun cycle ought to include daytime and nighttime.

Limitations

The scope of this project is constrained by the time. Therefore, only cumulus clouds will be modeled and no further weather conditions apart from one-directional wind will be incorporated. Depending on the rendering approach the overall scene might not run in real-time.

 

Technological approach

The weather data can be fetched from a web service such as OpenWeatherMap. This data should be used as input to the procedural cloud generator which will create volumetric cloud models. A rendering routine will then calculate the illumination of the scene from the intensity of the sun with respect to single forward scattering in the clouds. Also wave length dependent calculations to simulate sunrise and sunset should be executed. The generated models will be placed on a skydome in the scene and float with minor animations using Perlin noise or updating the cloud’s internal particles along the sky.

 

Perceptional research

To research the perceptional notion of a scene depending on the weather condition a survey will be conducted. It ought to examine the perception of the same underlying scene for different setups of the procedural weather generator. Also some research will investigate whether the generated sky contributes to making a scene more realistic.

Outline

The project is structured into several stages and the source code is available on GitHub.

1. Single Cloud - First, a single cloud is generated from geometric primitives.
2. Illumination - The cloud is illuminated according to the Phong illumination model.
3. Multiple Clouds - Several clouds are instanced and the model is elevated to a more realisitc and dynamic scene
4. Skydome - The sky component is developped and the illumination is discussed.
5. Procedural Sky - All components are combined into a single scene.

References

• http://openweathermap.org/
• A Real-Time Cloud Modeling, Rendering, and Animation System, J. Schpok, J. Simons, D. Ebert and C Hansen (2003)
• A New Application for Real-Time Shadow and Sun's Position in Virtual Environment, H. Kolivand and M. Sunar (2011)
• Cloud Modeling for Computer Graphics, G. Taxén (1999)
• Texturing & Modeling - A Procedural Approach, 3^rd edition, D. Ebert, F. Musgrave, D. Peachey, K. Perlin and S. Worley (2001)
• Real-Time Cloud Rendering, M. Harris and A. Lastra (2003)