How to convert FBX
to OBJ?

FBX

FBX (Filmbox) is a proprietary file format (.fbx extension) developed by Kaydara and owned by Autodesk since 2006. It is used to provide interoperability between digital content creation applications.

The format saw wider support from other 3D software packages such as Cinema 4D, SoftImage 3D, PowerAnimator, LightWave 3D and 3D Studio MAX. Today, FBX is also widely adopted among VR applications, which are typically built on top of major game engines.

OBJ

OBJ is a geometry definition file format (.obj extension) first developed by Wavefront Technologies for its Advanced Visualizer animation package.

The OBJ file format is a simple data-format that represents 3D geometry alone — namely, the position of each vertex, the UV position of each texture coordinate vertex, vertex normals, and the faces that make each polygon defined as a list of vertices, and texture vertices.

Vertices are stored in a counter-clockwise order by default, making explicit declaration of face normals unnecessary. OBJ coordinates have no units, but OBJ files can contain scale information in a human readable comment line.