When you want to display a complex 3D mesh in your 3D application, you must want to find an external model format for you to use. They would be COLLADA(.dae), FBX(.fbx), or OBJ(.obj). However, If you want to make a 3D engine, you must want to support more kinds of formats. Therefore, I start to research FBX SDK. FBX SDK supports .fbx, .dxf, .dae , and .obj file formats' importer/exporter, and .3ds format has been retired. FBX technology can be used to sharing scene assets, storing, packing models for sale, and processing animation, it supports import/export functions in Autodesk's products(3ds Max, Maya, AutoCAD...). The FBX SDK is a part of Autodesk FBX technology, it is C++ Software Development Kit. You can use it to create plug-ins, converters, and other applications. FBX SDK's source code is not public opening, therefore, we just can use their SDK interface, and if you want to redistribute or repacked, you should write permission from Autodesk, and include a link