Shading language

A shading language is a graphics programming language adapted to programming shader effects. Shading languages usually consist of special data types like "vector", "matrix", "color" and "normal". Shading languages used in offline rendering tend to be close to natural language, so that no special knowledge of programming is required. Offline rendering aims to produce maximum-quality images, at the cost of greater time and compute than real-time rendering. The RenderMan Shading Language (RSL or SL, for short), defined in the RenderMan Interface Specification, is a common shading language for production-quality rendering. It is also one of the first shading languages ever implemented. It defines six major shader types: Light source shaders compute the color of light emitted from a point on a light source to a point on a target surface. Surface shaders model the color and position of points on an object's surface, based on incoming light and the object's physical properties. Displacement shaders manipulate surface geometry independent of color. Deformation shaders transform the entire space. Only one RenderMan implementation, the AIR renderer by SiTex Graphics, implemented this shader type, supporting only a single linear transformation applied to the space. Volume shaders manipulate the color of light as it passes through a volume. They create effects such as fog. Imager shaders describe a color transformation to final pixel values. This is like an , except the imager shader operates on data prior to . Such data have more dynamic range and color resolution than can be displayed on a typical output device. Houdini VEX (Vector Expressions) shading language (often abbreviated to "VEX") is closely modeled after RenderMan. However, its integration into a complete 3D package means that the shader writer can access the information inside the shader, a feature that is not usually available in a rendering context. The language differences between RSL and VEX are mainly syntactic, in addition to differences regarding the names of several shadeop names.