The natural RenderMan coordinate system is a left-handed one in which the x-axis points to the right (blue), the y-axis points up (green), and the z-axis points into the screen (red).
Built-in Coordinate Systems
The built-in coordinate systems are those that are implicitly defined by the renderer or scene description. They may be queried by name from a valid geometry or shading context.
RenderMan provides no guarantee for what "current" space means at any time. If computations or pattern evaluation require an explicit coordinate system, shaders should transform data from "current" space into the desired space. Never assume that "current" space means anything particular.
User Defined Coordinate Systems
RenderMan allows users to define their own named coordinate systems for use in shading. These coordinate systems are bound to geometry instances and may be queried by name. Different geometry instances may bind to different coordinate systems of the same name. This is useful when "scoping" coordinate systems inside a scene hierarchyScoped coordinate systems are user defined spaces. They are typically used for custom 3d pattern lookups for displacement or shading. Scoped coordinate systems may vary per-object instance.