Those black lines are probably a z-buffer issue, most likely caused by the camera range you've set. The large camera range is probably diluting the z-buffer resolution too much - if you see what I mean. Just a guess.
If you're using such a large camera range because the meshes are so large, try scaling everything down and using the default camera range.
If you're using such a large camera range because the meshes are so large, try scaling everything down and using the default camera range.