opengl - Problem with glOrtho: the curve disappears from the scene

Question

I have curve, a parable (y=x*x) for x in [0, 10]. I have used:

glOrtho(-10 - 3, 10 + 3, -(y(10)+ 3) * (GLfloat) h / (GLfloat) w,
                        (y(10) + 3) * (GLfloat) h / (GLfloat) w, -1, 1);

a part on top is clipped. Moreover if I consider a parable in [8, 10] and I set:

glOrtho(-10 - 3, 10 + 3, -(y(10)+ 3) * (GLfloat) h / (GLfloat) w,
                        (y(10) + 3) * (GLfloat) h / (GLfloat) w, -1, 1);

my curve disappears from the scene. How can I modify the commands to visualize the curve?

Answer 1

等待大神答复