GEANT321/cgpack/cgbfit.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:19:41  cernlib
   6 * Geant
   7 *
   8 *
   9 #include "geant321/pilot.h"
  10 *CMZ :  3.21/02 29/03/94  15.41.31  by  S.Giani
  11 *-- Author :
  12       SUBROUTINE CGBFIT(FACE,ABCD,NT)
  13 ************************************************************************
  14 *                                                                      *
  15 *     Name: CGBFIT                                                     *
  16 *     Author: E. Chernyaev                       Date:    15.03.89     *
  17 *                                                Revised: S.Giani 1992 *
  18 *                                                                      *
  19 *     Function: Find all intersection points of face with plane        *
  20 *                                                                      *
  21 *     References: none                                                 *
  22 *                                                                      *
  23 *     Input: FACE(*) - face                                            *
  24 *            ABCD(4) - plane                                           *
  25 *                                                                      *
  26 *     Output: NT - number of intersections                             *
  27 *                                                                      *
  28 *                                                                      *
  29 ************************************************************************
  30 #include "geant321/cggpar.inc"
  31 #include "geant321/cgcedg.inc"
  32 #include "geant321/cgdelt.inc"
  33       REAL      FACE(*),ABCD(4)
  34 #if !defined(CERNLIB_SINGLE)
  35       DOUBLE PRECISION  A,B,C,D
  36 #endif
  37       INTEGER   KCG(6)
  38       DATA      KCG/KCGX1,KCGY1,KCGZ1,KCGX2,KCGY2,KCGZ2/
  39 *-
  40       ERROR  = EEWOR
  41       A      = ABCD(1)
  42       B      = ABCD(2)
  43       C      = ABCD(3)
  44       D      = ABCD(4)
  45 *      D1=0
  46 *      D2=0
  47       XDELT  = FACE(KCGBB)*C - B*FACE(KCGCC)
  48       YDELT  = FACE(KCGCC)*A - C*FACE(KCGAA)
  49       ZDELT  = FACE(KCGAA)*B - A*FACE(KCGBB)
  50       K      = 1
  51       IF (ABS(YDELT) .GT. ABS(XDELT))           K = 2
  52       IF (ABS(ZDELT) .GT. ABS(DELTA(K)))        K = 3
  53       IF(ABS(DELTA(K)).LT.ERROR)RETURN
  54       DD     = 1./ABS(DELTA(K))
  55       DELTA(1)  = DELTA(1) * DD
  56       DELTA(2)  = DELTA(2) * DD
  57       DELTA(3)  = DELTA(3) * DD
  58       KCG1   = KCG(K)
  59       KCG2   = KCG(K+3)
  60 *        F I N D   I N T E R S E C T I O N S   P O I N T S
  61       J      = LCGFAC - LCGEDG
  62       NT     = 0
  63       NEDGE  = FACE(KCGNE)
  64       DO 600 NE=1,NEDGE
  65         J      = J + LCGEDG
  66         D1     = A*FACE(J+KCGX1) + B*FACE(J+KCGY1) + C*FACE(J+KCGZ1) + D
  67         D2     = A*FACE(J+KCGX2) + B*FACE(J+KCGY2) + C*FACE(J+KCGZ2) + D
  68         IF (ABS(D1) .LE. ERROR)         D1 = 0.
  69         IF (ABS(D2) .LE. ERROR)         D2 = 0.
  70         IF (D1*D2 .GT. 0.)              GOTO 600
  71         NT     = NT + 1
  72         IF (D1.EQ.0. .AND. D2.EQ.0.)    GOTO 500
  73         IF (D1.LT.0. .OR.  D2.GT.0.)    TTT(2,NT) =-1.
  74         IF (D1.GT.0. .OR.  D2.LT.0.)    TTT(2,NT) =+1.
  75 *           D 1   O R   D 2   I S   N O T   Z E R O
  76         IF (NT .NE. 1)                  GOTO 400
  77         XA     = (D2*FACE(J+KCGX1)-D1*FACE(J+KCGX2)) / (D2 - D1)
  78         YA     = (D2*FACE(J+KCGY1)-D1*FACE(J+KCGY2)) / (D2 - D1)
  79         ZA     = (D2*FACE(J+KCGZ1)-D1*FACE(J+KCGZ2)) / (D2 - D1)
  80         TTT(1,1)   = 0.
  81         GOTO 600
  82   400   X      = (D2*FACE(J+KCG1)-D1*FACE(J+KCG2)) / (D2 - D1)
  83         TTT(1,NT)  = (X - AA(K)) / DELTA(K)
  84         GOTO 600
  85 *           D 1   A N D   D 2   B O T H   A R E   Z E R O
  86   500   IF (NT .NE. 1)                  GOTO 510
  87         XA     = FACE(J+KCGX1)
  88         YA     = FACE(J+KCGY1)
  89         ZA     = FACE(J+KCGZ1)
  90         TTT(1,1)   = 0.
  91         TTT(2,1)   = 0.
  92         GOTO 520
  93   510   X        = FACE(J+KCG1)
  94         TTT(1,NT)  = (X - AA(K)) / DELTA(K)
  95         TTT(2,NT)  = 0.
  96   520   NT       = NT + 1
  97         X        = FACE(J+KCG2)
  98         TTT(1,NT)  = (X - AA(K)) / DELTA(K)
  99         TTT(2,NT)  = 2.
 100         IF (TTT(1,NT) .GT. TTT(1,NT-1)) GOTO 600
 101         TTT(2,NT-1)= 2.
 102         TTT(2,NT)  = 0.
 103   600   CONTINUE
 104       RETURN
 105       END