So when i imported a missile i had made and textured in blender 3d the very back side of the front and back fins are blacked out whenever i render. I've changed every setting in every menu i can find and i still have no idea what is causing this. i went back and changed the texture so that the UV map is only on the missiles body and not on the fins at all and its still giving me the issue. any ideas
Either they are not assigned shaders or the normals are reversed.
The whole thing needs to be uvmapped -- assign one material to the whole thing. If they are still black then the normals of the fins are probably reversed.
Export the model as 3DS, then use PoseRay to convert to OBJ. Terragen likes PoseRay and xFrog models the best.
I've never used PoseRay for my models, though it seems very popular here. I'd check to be sure the shaders are assigned and the normals all face the proper direction first.