void WaterfallCurve (x, y, z, npts) D3AUX.C Level 3
float *x The array of the independent variable of the curve to be drawn.
 float y The value on the y-axis (going from front to back) at which the curve is to be drawn.
float *z The array of the dependent variable z(x) at y = const.
int npts The dimension of the x and z arrays.
WaterfallCurve() is usually used to display the a profile of some physical quantity at a number of fixed times. In 
order for hidden line removal to work properly, you must plot your curves starting from the end of the y-axis that is closest to your viewpoint. For example, if your viewpoint is from negative y, WaterfallCurve() should be called inside a loop with with the smallest value of y first.