Polygons disappearing on rotation

I am drawing a surface using trinagles and rotating it about the x and y axis. When I rotate it about the y axis it works fine. However, when I rotate it about the x axis large strips of polygons disappear. Furthermore, if I assign the surface a constant elevation of 0 the rotation about the x axis works fine. I am pretty new to OpenGL and am not sure what is going on. Thanks for any help you may be able to give.

I am not sure I understand your problem, but one thing to check is that the polygons aren’t just getting backface culled. If you have the line glEnable(GL_CULL_FACE) then when the polygon is facing away from you, it will not be drawn.

Another thing to check is that the rotation is doing what you expect. Plenty of times you will want the rotations to work one way but they will in fact do something else.

Thanks for your help. I figured out my problem. The znear I was using in gluPerspective was 0. I guess it was having problems with it. Thanks for your help anyway.