CSCE 4230  Program #6


        Due date:  Thursday, April 30, 2009


        Write an OpenGL program that displays a two-segment piecewise
        cubic (degree-3) Bezier space curve with continuous tangent
        vector at every point:  control points P0, P1, ..., P6, where
        P2, P3, and P4 are collinear.  

        Refer to Chapter 12 and bezcurve.c in the Redbook for an example
        of a one-segment Bezier curve.

        An interactive user must be allowed to zoom in or out, and to
        alter the viewing transformations with arrow keys and/or the
        mouse.

        Choose a default initial set of values for the seven control
        points, and allow the user to alter any one of them by dragging
        it with the mouse.  You might allow the user to select a control
        point by specifying its index (with a keypress or from the menu),
        in which case the control points must be labeled with their
        indices).  Alternatively, you may allow mouse selection by left-
        clicking on a point sufficiently close to the window coordinates
        of a control point.  Refer to functions gluProject and gluUnProject.
     
        If one of the three collinear control points is moved, collinearity
        must be restored by, for example, setting P3 to the midpoint
        between P2 and P4, or projecting one of them onto the line defined
        by the other two.



        Name your source code file Lastname_6.c or Lastname_6.cpp,
        where Lastname is your last name, 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.