The Development of a Method for Visually Simulating Clouds

Recently, computer graphics (CG) have been used to produce visual images not only for the movie industry, but also for a wide array of other uses such as simulating outdoor views in the landscape design and simulators for training different types of operators. In the future, high quality 3D graphics technology will undoubtedly be used to produce visual content. Against this backdrop, this study examines the creation of “clouds,” an essential element of outdoor imagery, and proposes a method for visually simulating cumulonimbus clouds using a particle base. To create images of outdoor scenes that contain clouds, actual visual images are taken of clouds (sky images), which are usually later color processed to match the intended scene. However, with this method it is difficult to create such scenery without taking actual video shots. The proposed method shows it makes possible to visually simulate cumulonimbus clouds billowing up from the inside. This is done using such means as a rising model using the flotation of cloud particle, a heat radiation model based on the entrainment effect of particles and air, a method for defining the initial temperature and vapor content of cloud particles using a 1/f noise map set on the earth’s surface, and a method for modifying the influenced area of the vortex field. The proposed method allows to make realistic visual simulation of cumulonimbus clouds, and to express images with higher degree of freedom by various camera angles and light source colors which are characteristics of CG. Thus with these methods, creators and designers who use CG for outdoor views will be able to automatically acquire motion data for clouds merely by inputting a set of parameters. This in turn will be able to reduce the workload involved in image production.