C ++********************************************************************
C                                                                      *
C  MRSCALE3                                                                    *
C                                                                      *
C **********************************************************************
C=* FROM: SPIDER - MODULAR IMAGE PROCESSING SYSTEM.   AUTHOR: J.FRANK  *
C=* Copyright (C) 1985-2005  Health Research Inc.                      *
C=*                                                                    *
C=* HEALTH RESEARCH INCORPORATED (HRI),                                *   
C=* ONE UNIVERSITY PLACE, RENSSELAER, NY 12144-3455.                   *
C=*                                                                    *
C=* Email:  spider@wadsworth.org                                       *
C=*                                                                    *
C=* This program is free software; you can redistribute it and/or      *
C=* modify it under the terms of the GNU General Public License as     *
C=* published by the Free Software Foundation; either version 2 of the *
C=* License, or (at your option) any later version.                    *
C=*                                                                    *
C=* This program is distributed in the hope that it will be useful,    *
C=* but WITHOUT ANY WARRANTY; without even the implied warranty of     *
C=* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
C=* General Public License for more details.                           *
C=*                                                                    *
C=* You should have received a copy of the GNU General Public License  *
C=* along with this program; if not, write to the                      *
C=* Free Software Foundation, Inc.,                                    *
C=* 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.      *
C=*                                                                    *
C **********************************************************************
C                                                                      *
C  MRSCALE3(RPT, VPT, SCALEI)                                                                    *
C                                                                      *
C  PURPOSE:                                                            *
C     COMPUTES THE SCALE FACTOR OF VPT WITH RESPECT TO RPT, USING ONLY
C     POINTS THEY HAVE IN COMMON. THIS THEN MUST BE APPLIED TO VPT
C     TO MAKE IT FIT TO RPT
C
C     USES ROOT OF RATIO BETWEEN SUM OF SQUARES OF COORDS OF RPT/VPT.
C
C INPUT:
C     RPT(3,LS)= COORDS OF POINTS IN REFERENCE VIEW
C     VPT(3,LS)= COORDS OF POINTS IN VIEW TO BE ADJUSTED
C COMMON INPUT:
C     NTPT = NUMBER OF POINTS
C OUTPUT:
C     SCALEI= SCALE FACTOR OF VPT VIEW WITH RESPECT TO RPT VIEW
C
C                                                                      *
C  PARAMETERS:                                                         *
C                                                                      *
C        0         2         3         4         5         6         7 *
C23456789012345678901234567890123456789012345678901234567890123456789012
C***********************************************************************

      SUBROUTINE MRSCALE3(RPT, VPT, SCALEI, NTPT, LS)

      DIMENSION         RPT(3,LS), VPT(3,LS)
      DOUBLE PRECISION  RSUM,VSUM

      RSUM = 0.0d0
      VSUM = 0.0d0

C     SUMS UP THE SQUARES OF THE COORDS
      DO  M=1,NTPT
          RSUM = RSUM+RPT(1,M)*DBLE(RPT(1,M))
     &        +RPT(2,M)*DBLE(RPT(2,M))+RPT(3,M)*DBLE(RPT(3,M))
          VSUM = VSUM+VPT(1,M)*DBLE(VPT(1,M))
     &	      +VPT(2,M)*DBLE(VPT(2,M))+VPT(3,M)*DBLE(VPT(3,M))
      ENDDO

      SCALEI = DSQRT(RSUM/VSUM)

      END