GEANT321/gphys/gfang.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:21:24  cernlib
   6 * Geant
   7 *
   8 *
   9 #include "geant321/pilot.h"
  10 *CMZ :  3.21/02 06/07/94  18.28.55  by  S.Giani
  11 *-- Author :
  12       SUBROUTINE GFANG(P,COSTH,SINTH,COSPH,SINPH,ROTATE)
  13 C.
  14 C.    ******************************************************************
  15 C.    *                                                                *
  16 C.    *  Finds theta-phi angles for a particle with director cosines P *
  17 C.    *  The logical flag ROTATE indicates whether the the director    *
  18 C.    *  cosines are along the Z axis (.FALSE.) or not (.TRUE.).       *
  19 C.    *                                                                *
  20 C.    *    ==>Called by :                                              *
  21 C.    *       Author    F.Carminati  *********                         *
  22 C.    *                                                                *
  23 C.    *                                                                *
  24 C.    ******************************************************************
  25 C.
  26       DIMENSION P(*)
  27 #if !defined(CERNLIB_SINGLE)
  28       DOUBLE PRECISION DUX, DUY, DUZ, DSITH2, ONE, DNORM
  29 #endif
  30       LOGICAL ROTATE
  31       PARAMETER (ONE=1)
  32 C.
  33 C.    ------------------------------------------------------------------
  34 C.
  35       DUX      = P(1)
  36       DUY      = P(2)
  37       DUZ      = P(3)
  38       ROTATE   = .TRUE.
  39       IF(ABS(DUZ).GE.0.85) THEN
  40          DSITH2=DUX**2+DUY**2
  41          IF(DSITH2.GT.0.) THEN
  42             COSTH  = SIGN(ONE,DUZ)*SQRT(ONE-DSITH2)
  43             DSITH  = SQRT(DSITH2)
  44             SINTH  = DSITH
  45             COSPH  = DUX/DSITH
  46             SINPH  = DUY/DSITH
  47          ELSEIF(DUZ.GT.0.)THEN
  48             ROTATE = .FALSE.
  49             COSTH =  1.
  50             SINTH =  0.
  51             COSPH =  1.
  52             SINPH =  0.
  53          ELSE
  54             COSTH = -1.
  55             SINTH =  0.
  56             COSPH =  1.
  57             SINPH =  0.
  58          ENDIF
  59       ELSE
  60          COSTH  = DUZ
  61          DSITH  = SQRT((ONE+DUZ)*(ONE-DUZ))
  62          SINTH  = DSITH
  63          DNORM  = ONE/SQRT(DUX**2+DUY**2)
  64          COSPH  = DUX*DNORM
  65          SINPH  = DUY*DNORM
  66       ENDIF
  67 *
  68       END