plpoly3: Draw a polygon in 3 space 

DESCRIPTION:

    Bugs:  If one of the first two segments is of zero length, or if they
    are colinear, the calculation of visibility has a 50/50 chance of
    being correct.  Avoid such situations :-).	See x18c.c for an example
    of this problem. (Search for 20.1). 

SYNOPSIS:

plpoly3(n, x, y, z, draw, ifcc)

ARGUMENTS:

    n (PLINT, input) :      Number of points defining line. 

    x (PLFLT *, input) :    Pointer to array with x coordinates of points. 

    y (PLFLT *, input) :    Pointer to array with y coordinates of points. 

    z (PLFLT *, input) :    Pointer to array with z coordinates of points. 

    draw (PLBOOL *, input) :    Pointer to array which controls drawing
    the segments of the polygon.  If draw[i] is true, then the polygon
    segment from index [i] to [i+1] is drawn, otherwise, not. 

    ifcc (PLBOOL, input) :    If ifcc is true the directionality of the
    polygon is determined by assuming the points are laid out in a
    counter-clockwise order.  Otherwise, the directionality of the
    polygon is determined by assuming the points are laid out in a
    clockwise order.