i7lin3.F

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!||====================================================================
!||    i7lin3   ../starter/source/interfaces/inter3d1/i7lin3.F
!||--- called by ------------------------------------------------------
!||    i2bar3   ../starter/source/interfaces/inter3d1/i2dst3.F
!||====================================================================
      SUBROUTINE i7lin3(XI,YI,ZI,XA,YA,ZA,XB,YB,ZB,NX,NY,NZ,P,ALP)
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-----------------------------------------------
C     REAL
      my_real
     .    xi,yi,zi,xa,ya,za,xb,yb,zb,nx,ny,nz,p,alp
C-----------------------------------------------
C   L o c a l   V a r i a b l e s
C-----------------------------------------------
C     REAL
      my_real
     .    xab,yab,zab,
     .    xp,yp,zp,norm
C
      xab = xb - xa
      yab = yb - ya
      zab = zb - za
C
      alp = (xi-xa)*xab + (yi-ya)*yab + (zi-za)*zab
      norm = max(em20, xab**2 + yab**2 + zab**2)
      alp = alp / norm
      alp = max(zero,alp)
      alp = min(one,alp)
C
      xp = xa + alp*xab 
      yp = ya + alp*yab 
      zp = za + alp*zab
C
      nx = xi -xp 
      ny = yi -yp 
      nz = zi -zp
C
      p = sqrt(nx**2 + ny**2 +nz**2)
      norm = max(em20,p)
C
      nx = nx / norm
      ny = ny / norm
      nz = nz / norm
C
      RETURN
      END