***********************************************************************
c     
      SUBROUTINE RPCSTEP
c     
c     
c     Last modified on 11/08/2007  by D. Gonzalez-Diaz
c     
***********************************************************************
      IMPLICIT NONE

#include "geant321/gcflag.inc"
#include "geant321/gckine.inc"
#include "geant321/gcsets.inc"
#include "geant321/gctmed.inc"
#include "geant321/gctrak.inc"
#include "geant321/gcvolu.inc"
#include "rpctuple.inc"

      INTEGER NH
      PARAMETER (NH=14)
      REAL HITS(NH)
      REAL XM(3), XD(3), PM(3), PD(3)
      CHARACTER*4 CHSET
      EQUIVALENCE (IHSET,CHSET)
      INTEGER I, IHIT, DETNR
      REAL ELOS, LENGTH_IN
      SAVE ELOS, LENGTH_IN

      IF(CHSET.NE.'RPCG') RETURN ! are we in an RPC gap(active volume)?
      
      DETNR = IDTYPE - 500       

      ! accumulate the energy deposited by the particle
      IF(INWVOL.EQ.1) THEN
         ELOS = 0.0      
         LENGTH_IN = SLENG
      ENDIF
      
      ELOS  = ELOS + DESTEP      
 
      ! condition for storing a hit in the volume:
      ! "CHARGED PARTICLE GOING OUT, STOPPED OR DECAYED" (Including the
      ! two last have no visible effect whatsoever in this case)
      ! In order to store also NEUTRAL particles that may create a hit in EBOX, *any* particle
      ! can additionally create a hit "WHEN GOING OUT, STOPPED OR DECAYED" from the virtual box 
      ! (DETNR.EQ.-1). There are plenty of neutral particles just 'punching through' that are filtered 
      ! later on in fillrpc.cc

      IF(((INWVOL.EQ.2 .OR. ISTOP.GE.1) .AND. CHARGE.NE.0).OR. 
     &   ((INWVOL.EQ.2 .OR. ISTOP.GE.1) .AND. DETNR.EQ.-1)) THEN

         DO I=1,3
            XM(I) = VECT(I)
            PM(I) = VECT(I+3)
         ENDDO


         NLEVEL=3                ! Geometry level for transforming to module ref system (EBOX)  

         IF(DETNR.EQ.-1) THEN
            
            DETNR=0              ! Just because HITS(7) must be positive [??]. This is not relevant since
                                 ! the detectorID for EBOX is assigned in rpcdigi.F to -SECTOR.
         ENDIF                   
         
         CALL GMTOD(PM,PD,2)     ! transform momentum    into module ref system (EBOX)
         CALL GMTOD(XM,XD,1)     ! transform coordinates into module ref system (EBOX)

         HITS(1)  = -XD(1)            ! x of hit in detector coordinates (the minus sign is needed)
         HITS(2)  = -XD(2)            ! y              "                 (the minus sign is needed)
         HITS(3)  = XD(3)             ! z              "
         HITS(4)  = TOFG              ! tof of hit
         HITS(5)  = FLOAT(ITRA)       ! track nb.
         HITS(6)  = ELOS              ! deposited energy
         HITS(7)  = FLOAT(DETNR)      ! DETECTOR number
         HITS(8)  = VECT(7)           ! total momentum of particle
         HITS(9)  = SLENG             ! length of the current track
         HITS(10) = SLENG - LENGTH_IN ! local track length (used for energy loss estimates)
         HITS(11) = -PD(1)            ! Px/P (the minus sign is needed)
         HITS(12) = -PD(2)            ! Py/P (the minus sign is needed)
         HITS(13) = PD(3)             ! Pz/P
         
         CALL GSAHIT(ISET,IDET,ITRA,NUMBV,HITS,IHIT) ! store hit for geant digitization

      ENDIF

      RETURN
      END