CS-560, Assignment # 7
Due Date: 4/26/02

In this assignment you are do write a Visual C++ MFC program that allows
the user to draw, modify, extend, and transform a B-Spline curve. There 
should be a menu with the following items: "B-Spline", "Translate", "Scale",
"Rotate", "Extend". When the user selects "B-Spline" the user should be
allowed to input any number of control points with the mouse. Each click of
the left-hand mouse button provides a new control point, which should be
drawn as a small rectangle on the screen. A click of the right mouse
button should then cause the program to draw the uniform cubic B-spline
polynomial curve determined by the control points that were entered. After
the B-Spline is drawn, the program should enter a mode in which it permits
the user to use the left-hand mouse button to adjust the curve by moving
any of its control points. Pressing the left-hand mouse button over a
control point selects that point. While the button is down, the user moves
the mouse to the new position of the control point. Releasing the left-
hand button should cause the control point's rectangle to be repositioned
at the new cursor location and the B-Spline curve to be redrawn. (The old
control point and curve should, of course, disappear.) The user should be
able to perform this readjustment of the curve as many times as desired
with any of the control points. A click of the right-hand mouse button
should permit the user to go back to the menu to choose another option.

If you wish (preferably), you may implement the adjustment of the curve
using a "rubberband" technique in which the curve stretches and contracts
while the user is moving a control point with the left-hand mouse button
down. The curve should be made "permanent" when the user releases the left
mouse button. This adjustment of the curve by moving selected control
points should continue until the user selects some other menu item.

Regardless of which way you do the adjustment of the curve, for enhanced
performance, the forward difference method discussed in class must be
used any time the curve is plotted.

"Translate"--Choosing this menu item should enable the user to translate
the B-Spline curve in the drawing area. Subsequently the user should be
permitted to click somewhere in the drawing area. The point selected will
be the new location of the first (P0) control point of the B-Spline curve.
The program will then move P0 to the selected location and all the other
control points will then be translated by an equal amount. Finally the
curve will be redrawn according to the new locations of the control
points.

"Scale" or "Rotate" menu items should enable the user to change the size
or orientation of the B-Spline curve. Selecting either of these two menu
items should allow the user to click on some point in the drawing area.
The curve should then be scaled with respect to that point or rotated
about that point by a fixed amount. The details of how this is done are 
up to you. Try to make it as intuitive and user friendly as possible. (You
may want to use "Scale Up", "Scale Down", "Rotate Clockwise", and "Rotate
Counter Clockwise" menu items here.)

"Extend"--Each time this menu item is selected, the program should allow
the user to input a control point (with the mouse) that will be used to
attach a new B-Spline curve segment to the end of the previous one, thus
extending the B-Spline curve.