im not sure if this is what you were asking capu.but this process is called baking
after making the highpoly, we make a seperate mesh ontop , keeping in mind the volume and matching it as close as possible, on baking it we get this blue map(normal map) and a white shadowmap( AO), you can see these maps in my texture sheet. these two maps are the main one, while the AO map gives shadow and shades, the blue map calculates how the surface is suppose to look when you shine light on it, this information is taken form the highpoly.
the AO map is not actually used as a seperate map, it mainly used to add the shadow and shades to the diffuse map, witch is just flat colors without it
also the mesh is not all quads,it doesnt have to be. its needed only around the joints for animation.
im posting some early wips i did when i was working on this…
[]
[]
[]
[]
[]