gluLookAt doesn't work as expected - opengl

Question

I have this function of drawing a circle:
void draw_circle()
{
GLint num_of_tri = 32;
GLfloat vertex[3];
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
const GLfloat delta_angle = 2.0*PI/float(num_of_tri);
//Draw Front tire
glBegin(GL_TRIANGLE_FAN);
glColor3f(0.5, 0.5, 0.5);
vertex[0] = vertex[1] = vertex[2] = 0.0;
glVertex3fv(vertex);
for(int i = 0; i < num_of_tri ; i++)
{
vertex[0] = cos(delta_angle*i) * wheelRadius; //wheelRadius is 1.0
vertex[1] = sin(delta_angle*i) * wheelRadius;
vertex[2] = 0.0;
glVertex3fv(vertex);
}
vertex[0] = 1.0 * wheelRadius;
vertex[1] = 0.0 * wheelRadius;
vertex[2] = 0.0;
glVertex3fv(vertex);
glEnd();
}
This is my init function
void init(void)
{
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0.0, 0.0, 1.5, 0, 0, 0, 0, 1, 0);
}
And this is my display function
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
draw_circle();
glFlush();
}
To my best understanding, the circle is drawn at the origin. So calling the gluLookAt function with eye values of (0,0,1.5) is not a problem right?
But whenever I'm calling gluLookAt with eye values of z, bigger than 1, the circle disappears. Why does this happen?
Any help would be appreciated.

Answer 1

You are missing a call to gluPerspective.
The default zNear and zFar values of (-1,1) exclude your circle when you move the eye point more than one unit away.
Edit your init function to include:
gluPerspective( 45.0f, ( GLfloat )screenWidth / ( GLfloat )screenHeight, 0.1f, 100.0f );
Or something similar.