A Model for Description and Synthesis of Heterogeneous Textures

Existing texture models either describe textures as a non-hierarchical surface property (by means of Markov chains, time series and other stochastic methods) or distinguish only between micro and macro textures. Besides this, textures are used in general only for mapping colour-information (usually derived from digitized photographs) on the object surface or for varying the normal vector of a given surface (bumps mapping). In addition, the different models are strongly combined with special generation algorithms and the produced textures are exclusively raster images. As a consequence, the above models are not able to describe more than a few types of textures. In this paper a definition of the term texture is first presented and a hierarchical texture model in accordance with the above definition is then proposed. We provide complete textures, consisting of several slices, to be mapped on geometrical objects. Each slice represents an optical surface property. These properties are appriximated by the different parameters of an illumination model. The slices themselves are hierarchical compositions of several levels. Each "intermediate texture" is derived by operations (transformations and combinations) performed on the textures of the next lower level. A texture is not limited in space and is described by means of a complete texture function which affects all texture slices. Such functions can be either usual algebraical functions, or they can determine the placement of elements on the texture plane.(AGD