How to modify the .obj so our character can move?
Better use .md2, .md3 (quake) or other filetype instead since they're made for this kind of stuff.
Hi Farabi,
You're in for a lot of trouble using animated OBJ files: you will need some kind of bones-engine that moves the limbs of a character as OBJ files themselves don't have bone info. Have a look at e-Frontier's (formerly Curious Labs) Poser 5/6 at http://www.e-frontier.com/, in the Download area you might find some docs that will help you a bit.
A Poser OBJ file usually contains groups which make up a character: head, chest, abdomen, hip, left-buttock, right-buttock, etc...
As an OBJ only contains vertex, texture coordinate, group and face information you will need another file per OBJ telling the engine how the different body parts (groups) are joined, what their moving/rotation point is, limits of movement (a head really can't rotate 360 degrees), how the vertices of adjoining groups should be smoothed, not to mention bulging and denting of muscles.
Poser's main character file format is the CR2 file (not to be confused with Canon's raw image file, also CR2). This is a plain text file with incorporates all this info, as well as shader/texture info and a lot more.
Simply rotating/moving/bending around some local axis is not enough....
Maxx
P.S.: Select Poser 5 downloads at e-Frontier, this area has the complete user manual in PDF format.