The mental ray Base Shader Library is a set of simple shaders designed to form the standard building blocks of Phenomenon scene elements. They perform functions useful in many different contexts, and are not tied to specific types of shaders. A base shader is not inherently a material or light shader but can be used to build a Phenomenon used in place of a material or light shader. This means that base shaders must be as generic as possible. They avoid interdependencies that would limit their applicability.