Recently, I am working on a project about using VR CardBoard to view the 3D models or worlds created on VRMath2 website. So far, a prototype is avaiable for iPhone (tested on iPhone 6 only) capable of viewing most x3d files generated from VRMath2 Editor. However, there is no easy interface yet from it (mobile in CardBoard) to navigate x3d files. But there are three ways to start with.
