void draw_cylinder(GLfloat radius,
                   GLfloat height,
                   GLubyte R,
                   GLubyte G,
                   GLubyte B)
{
    GLfloat x              = 0.0;
    GLfloat y              = 0.0;
    GLfloat angle          = 0.0;
    GLfloat angle_stepsize = 0.1;

    /** Draw the tube */
    glColor3ub(R-40,G-40,B-40);
    glBegin(GL_QUAD_STRIP);
    angle = 0.0;
        while( angle < 2*PI ) {
            x = radius * cos(angle);
            y = radius * sin(angle);
            glVertex3f(x, y , height);
            glVertex3f(x, y , 0.0);
            angle = angle + angle_stepsize;
        }
        glVertex3f(radius, 0.0, height);
        glVertex3f(radius, 0.0, 0.0);
    glEnd();

    /** Draw the circle on top of cylinder */
    glColor3ub(R,G,B);
    glBegin(GL_POLYGON);
    angle = 0.0;
        while( angle < 2*PI ) {
            x = radius * cos(angle);
            y = radius * sin(angle);
            glVertex3f(x, y , height);
            angle = angle + angle_stepsize;
        }
        glVertex3f(radius, 0.0, height);
    glEnd();
}