Lighting -> verry fuzzy spotlight

Hi, i’m a Student diong an internship, i have a research assignment where the goal is to make a OpenGL 3D reprisentation of 2D MRI scanner data.

I am at the point that i have the model and all, but since the reprisentation is a hart chamber (left ventrikular) it’s in 1 color. The single color prevented seing depth, so i started working with lighting.

I have ambient light (works fine), and a stationary spotlight to create a shade in order to get depth. This works good but when i rotate the object arround the x or y axis then i see that the other side does not get illuminated even though the light is shining directly on it. It does however work with rotations arround the Z axis (unless already dark).

An example from another company of this viewing module can be found here :

The bands of the model are made up out of triangle strips and fan’s. and i do not use culling or resize or anything like that that could invalidate the normals.

Plz help me,… i tried everything.
I can’t find a solution

My guess is that you are not rotating the light with your scene correctly. It may help to draw a box where your light is so you can make sure the light is pointing where you think it is.