GEANT321/ggeom/gvgrad.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:20:57  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 *
  13       SUBROUTINE GVGRAD (XYZ, C, NC, GRA)
  14 ************************************************************************
  15 *                                                                      *
  16 * GVGRAD calculates the gradient vector of a surface         VP 880314 *
  17 *                                                                      *
  18 * Input  : XYZ     coordinates of the point                            *
  19 *          C(1)       number of non constant coefficients of the       *
  20 *                        surface                                       *
  21 *          C(2),C(3),... non constant coefficients of the surface      *
  22 *          NC      total number of coefficients of the surface         *
  23 *                                                                      *
  24 * Output : GRA     gradient vector of the surface                      *
  25 *                                                                      *
  26 ************************************************************************
  27       REAL           XYZ(3) , C(*), GRA(3)
  28 *-----------------------------------------------------------------------
  29 *
  30 *     case with simplified surface X=C0, Y=C0, Z=C0, X*2+Y*2=C0
  31 *     (happens only when initialisation is done)
  32 *
  33       IF (NC.EQ.2)              THEN
  34         IAX = C(2)
  35         IF (IAX.LE.3)           THEN
  36           GRA(1) = 0
  37           GRA(2) = 0
  38           GRA(3) = 0
  39           GRA(IAX) = 1
  40         ELSE
  41           GRA(1)   = 2.*XYZ(1)
  42           GRA(2)   = 2.*XYZ(2)
  43           GRA(3)   = 0.
  44         ENDIF
  45         GO TO 999
  46       ENDIF
  47 *
  48 *     case with surfaces with 4, 7 or 10 coefficients (normal case)
  49 *
  50       GRA(1) = C(2)
  51       GRA(2) = C(3)
  52       GRA(3) = C(4)
  53       IF (NC.EQ.4)              GO TO 999
  54 *
  55 *     case with surfaces with 7 or 10 coefficients
  56 *
  57       DO 100 I = 1,3
  58   100   GRA(I) = GRA(I) + 2.*C(I+4)*XYZ(I)
  59       IF (NC.NE.10)             GO TO 999
  60 *
  61 *     case with surfaces with 10 coefficients
  62 *
  63       GRA(1)   = GRA(1) + C(8)*XYZ(2)+C(10)*XYZ(3)
  64       GRA(2)   = GRA(2) + C(8)*XYZ(1)+C( 9)*XYZ(3)
  65       GRA(3)   = GRA(3) + C(9)*XYZ(2)+C(10)*XYZ(1)
  66
  67   999 RETURN
  68       END