CSCE 4230  Program #2


        Due date:  Thursday, February 19, 2009


        Write an interactive OpenGL program that displays a rotating
        pendulum, centered in the window.  The pendulum consists of
        a bob of radius r attached to an anchor point (the origin of
        the object coordinate system) by a rigid wire of length l,
        where r and l are global variables.  Use r = 1.0 and l = 10.0.
        Modify double.c (OpenGL Programming Guide, pp. 24-25) as follows.

          1)  Replace display by a function that renders the pendulum
              with the bob rotated through angle spin from the vertical
              rest position.  Draw a dot for the anchor point, a line
              segment for the wire, and a disk of radius r for the bob.
              Refer to OpenGL functions gluDisk, gluNewQuadric, and
              gluQuadricDrawStyle for drawing the disk.

          2)  In reshape, preserve the square aspect ratio, and define
              the view volume to be [-a,a] X [-a,a] for a = 1.25*l.

          3)  Add a keypress-handling function and a menu attached to
              the right mouse button with a keypress associated with
              each menu option for the following key/option pairs:

              a)  '+':  start the pendulum spinning counterclockwise
                  by setting the spin increment to a positive value
                  and registering spinDisplay as the idle callback;
              b)  '-':  start the pendulum spinning clockwise by
                  setting the increment for spin to a negative value
                  and registering spinDisplay as the idle callback;
              c)  <space> (ASCII 32):  stop the spin by registering
                  NULL as the idle callback;
              d)  <escape> (ASCII 27):  terminate the program (exit).

        The main program should call a function that creates the menu
        (by calling glutCreateMenu, glutAddMenuEntry, and glutAttachMenu)
        and registers a callback for the keypresses with glutKeyboardFunc
        (in addition to the mouse callback).  The keyboard callback
        function should simply call the menu callback function.  Function
        mouse in double.c need not be altered.

        Name the source code file prog2.c or prog2.cpp, and email it to 
        the grader, Ismail Mohammed:  im0058@unt.edu.

        Also, hand in a source code listing (with your name on it),
        at the beginning of class on the due date.