OpenGL Can't draw z axis - opengl

Question

Im very new to OpenGL and can't understand why my code doesn't work.
It is supposed to draw 3 axis: x y and z. But only x and y are displayed.
int main()
int main(int argc, char * argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
glutInitWindowSize(800, 600);
glutCreateWindow("OpenGL lesson");
glutReshapeFunc(reshape);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
void reshape ()
void reshape(int w, int h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-15, 15, -15, 15, -15, 15);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClearColor(1, 1, 1, 0);
}
void display()
void display()
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINES);
// draw line for x axis
glColor3f(1.0, 0.0, 0.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(10.0, 0.0, 0.0);
// draw line for y axis
glColor3f(0.0, 1.0, 0.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 10.0, 0.0);
// draw line for Z axis
glColor3f(0.0, 0.0, 1.0);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(0.0, 0.0, 10.0);
glEnd();
glutSwapBuffers();
}
Could someone help, please?

Answer 1

Axiz Z is drawn, but due to the camera's default position, there will be just a single pixel drawn.
The camera's default position is looking in the Z direction, perpendicular to the XY plane. You might want to look into gluLookAt to place your camera elsewhere or gluPerspective for a different viewing volume (more commonly used for 3D rendering than glOrtho).