BRL-CAD has support for dozens of different 3D geometry file formats. We do not, however, have an importer for the X3D geometry format.
Your project involves implementing import support for the X3D file format as robustly and comprehensively as possible. There are several potential 3rd party libraries that can be used or (not recommended, but acceptable) you can write your own parser library. You'll minimally need to implement import support for all geometry entities including polygonal and NURBS geometries, any hierarchical information, material properties, and (time permitting) faithful round-tripping (import and export).