There is an interesting opportunity to add some extra details to your 3D model without adding any excess tris to its geometry. A regular object is wrapped by a special texture that stores some relief information. It is like putting on a dress made of cloth with bulging patterns. That is a very smart technical solution. A bitmap document keeps information about the heights of a specific region of an object. The data can be transferred and compressed as regular raster graphics. There is no need of special file formats. Such a method is known as bump mapping because various elements of 3D relief, called bumps for the sake of simplicity, are projected onto a flat image turning into a map.
Classical bump maps are grayscale maps where heights are coded by a pixel's brightness. A 3D engine wraps such a texture on an object but does not display it in a straight form. It only uses it for simulation of extra geometry (generating both concave and convex elements). All graphic...