Previous: hzngv Up: ../plot79_h.html Next: hznnh

HZNIL

       SUBROUTINE  HZNIL (CROSS, T, XC,YC, X1,Y1, X2,Y2, X3,Y3, X4,Y4)
 C$    (Intersection of Lines)
 C$    Given two line segments 1--2 and 3--4, determine the  point
 C$    (XC,YC) at which the segments cross.  The crossing point is
 C$    represented in parametric form as
 C$
 C$    (XC,YC) = (1-T)*(X1,Y1) + T*(X2,Y2)
 C$            = (1-S)*(X3,Y3) + S*(X4,Y4)
 C$
 C$    On return,  CROSS is  set .TRUE.  if the  lines cross,  and
 C$    .FALSE.  if they are parallel.  If they cross, then (XC,YC)
 C$    is the crossing point,  and the value of  T can be used  to
 C$    determine whether the  crossing point lies  on the  segment
 C$    1--2, since  then T  is in  the range  0..1.  If  CROSS  is
 C$    .FALSE., then T and (XC,YC) are undefined.
 C$    (04-FEB-82)