I begin loading a terragen exported obj, but the result terrain was very "flat".
To calculate the lighting, i think, the render engine use the material of the face, the light sources and the face normal. Also it´s use the vertex color.
When you load and obj without material/normals, you can generate it. Extends DefaultNodeFactory class and make the work that blender do for me. It´ll been a better method than mine.
Someone know, if in xith, are something like Java3D's NormalGenerator?? Having the face with her 3 vertex, it´s may be easy to obtain the normal.