When a shader requires an input of a coordinate system or you need to place a procedural object, we can create a null OBJ. In the Render TAB of the null OBJ, turn on Output transform as render space (RIB/IFD). This will output RiCoordinateSystem with the null OBJ's transformation.
To use it in the shader, drag the path of this null OBJ to the shader parameter. For example: