I got a nicely shaded model, but the position of the light does not look consistent. Some of the faces of the object seems to shade in a different - almost opposite- way of what is expected.
Does to direction of the normal matter? Is the backside of a triangle shaded the same as the front side when subjected to light?
If not, is there some way of making OPENGL ignore if the normals are consistent or reversed. My CAD data does not make sure all normals point in the same direction. Some surfaces point in the opposite direction and I do not want to mess with correction algorithms etc.