seg_intersect.F File Reference

#include "implicit_f.inc"

Go to the source code of this file.

Functions/Subroutines
integer function	seg_intersect (x1, y1, x2, y2, x3, y3, x4, y4, xint, yint, idebug)

Function/Subroutine Documentation

seg_intersect()

integer function seg_intersect	(		x1,
			y1,
			x2,
			y2,
			x3,
			y3,
			x4,
			y4,
			xint,
			yint,
		integer	idebug )

Definition at line 29 of file seg_intersect.F.

C-----------------------------------------------
C   I m p l i c i t   T y p e s
C-----------------------------------------------
#include      "implicit_f.inc"
C-----------------------------------------------
C   D u m m y   A r g u m e n t s
C-----------------------------------------------
      my_real  :: x1,y1,x2,y2,x3,y3,x4,y4,xint,yint,ratio
C-----------------------------------------------
C   L o c a l   V a r i a b l e s
C-----------------------------------------------
      INTEGER  :: OK,IDEBUG
      my_real  :: ax,bx,ay,by,cx,cy,sy,sx,dm,alpha,beta,tol
c----------------------------------------------------------
c     calcule intersection de deux segments en 2D : N1-N2 et N3-N4
c     intersection trouve => OK=1, sinon OK=0
c     alpha, beta = ratio du point intersection de chaque segment
C=======================================================================
      ok = 0
      ax = x2 - x1
      ay = y2 - y1
      bx = x4 - x3
      by = y4 - y3
c
      dm = ay*bx - ax*by
      IF (dm /= zero) THEN  ! les lignes ne sont pas paralleles
        cx = x3 - x1
        cy = y3 - y1
c
         alpha = (bx * cy - by * cx) / dm
         beta  = (ax * cy - ay * cx) / dm
c
         IF (alpha >= zero .and. alpha <= one .and.
     .       beta  >= zero .and. beta  <= one) THEN
           ok = 1
           xint = x1 + alpha * ax
           yint = y1 + alpha * ay
         ENDIF
c         IF (IDEBUG == 1) print*,'ALPHA,BETA=',ALPHA,BETA
       ENDIF
       seg_intersect = ok
c-----------
      RETURN