Shading language

A shading language is a graphics programming language adapted to programming shader effects (characterizing surfaces, volumes, and objects). Such language forms usually consist of special data types, like "color" and "normal". Due to the variety of target markets for 3D computer graphics, different shading languages have been developed.

Shading languages used in offline rendering produce maximum image quality. Material properties are totally abstracted, little programming skill and no hardware knowledge is required. These kind of shaders are often developed by artists to get the right "look", just as texture mapping, lighting and other facets of their work.

Processing such shaders is time-consuming. The computational power required can be expensive because of their ability to produce photorealistic results. Most of the time, production rendering is run on large computer clusters.

The RenderMan Shading Language (often referenced as RSL or SL, for short), which is defined in the RenderMan Interface Specification is the most common shading language for production-quality rendering. It is also one of the first shading languages ever implemented.

The language defines six major shader types:

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.

Gelato's shading language, like Houdini's VEX, is closely modeled after RenderMan. The differences between Gelato Shading Language and RSL are mainly syntactical — Gelato uses semicolons instead of commas to separate arguments in function definitions and a few shadeops have different names and parameters.

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