OpenGL Can't draw z axis

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).