CRES
From SimsWiki
Resource Node
This datatype is the head of a Scenegraphic chain. Often referred to as the CRES (4-letter identifier for the internal name cResourceNode) , the Resource Node contains all elements of a Scenegraphic Chain, very much like a 3D graphic Scene. It defines the properties, position, and orientation of the Geometry, Lights, Cameras, Animation Helpers(IK Poles(Maya specific controller), IK Targets, often present in character "Rigs"), and SLOT resource(in its latest format)
Modding the Resource Node
File Format
This file type uses the Graphics resource format RCOL.