If the Maya primitive has an attached reference geometry then 3Delight for Maya can output it along with the rendered object. Reference geometry can be accessed in the shaders using the Pref and NRef variables.
Output Pref
When this attribute is on, the geometry passed to 3Delight will also contain reference geometry that represents geometry before any deformation has been applied to it. This geometry is accessible to any shader that declares the varying point Pref parameter. This attribute is off by default.
Output Nref
If checked, geometry passed to 3Delight will also contain reference normals; those are normals before any deformation has been applied. These non deformed normals are accessible to shaders that declare the varying normal Nref parameter. This attribute is off by default.