MetaShaders are shaders that are capable of supporting several renderers simultaneously. Many of the shaders that ship with Softimage are capable of supporting different renderers --for example, users can set up a single render trees to display both mental ray and Cg rendering effects.
You can create MetaShaders that enable users to access multiple rendering engines from a single interface. This is enabled by changes to the SPDL file structure which allow you to define a single parameter block to control multiple rendering implementations. MetaShaders are also supported by new querying methods on the Shader object/class that allow you to read the parameters specified in the SPDL file.
Autodesk Softimage v7.5