I wrote a very simple program and faced with a next thing.
I am drawing the next picture : there is a plane drawed by a rectangle function, from one side of the plane there is a directed light source, and from the opposite site there is a sphere. The problem is next i cannot observe light on the rectangle, but i can see it on the sphere, when the cut off angle is small. But when i increase a cut off angle i see alight of whole plane. I can’t see the real light effect on the plane.
To solve this problem i can do next :
to break to smaller pieces my entire plane and this solution works.
But this is some harder job for PC to draw a lot of rectangles than just one.
So are the some specific functions in OpenGL to overcome this problem?