File Format: 3DS and OBJ
The 3ds file format is made up of chunks. They describe what information is to follow and what it is made up of, it’s ID and the location of the next block. If you don’t understand a chunk you can quite simply skip it. The next chunk pointer is relative to the start of the current chunk and in bytes. The binary information in the 3ds file is written in a special kind of way. Namely the lest significant byte comes first in an int.
Most of the time, the exported 3DS will comes compacted with their texture files such as JPEG, BMP, PNG, TIFF or TGA (targa).
Please see Appendix A for more details.
Object files define the geometry and other properties for objects. They can be in ASCII format (.obj) or binary format (.mod). The .obj file format supports both polygonal objects and free-form objects. Polygonal geometry uses points, lines, and faces to define objects while free-form geometry uses curves and surfaces.
the exported OBJ will comes with the MTL (Material) file, which contains texture and material settings.
Please see Appendix B for more details.