;+
;
; @file_comments
; compute the 3D e3u from e3t and e3t_ps
;
; @categories
; diagnostics
;
; @keyword e1 {default=0}{type=scalar: 0 or 1}
; activate to compute e1u * e3u instead of e3u
; note that of both keywords e1 and e2 are acticated we compute e1u * e2u * e3u instead of e3u
;
; @keyword e2 {default=0}{type=scalar: 0 or 1}
; activate to compute e2u * e3u instead of e3u
; note that of both keywords e1 and e2 are acticated we compute e1u * e2u * e3u instead of e3u
;
; @returns
; e3u 3D array
;
; @uses
; cm_4mesh.pro
;
; @history
; Sebastien Masson, Jan 2011
;
; @version
; $Id$
;
;-
function e3u_3d, e1 = e1, e2 = e2
;
  compile_opt idl2, strictarrsubs
;
@cm_4mesh
;
  IF keyword_set(key_partialstep) THEN lastx = ( lastxu + 1 ) < ( jpi - 1 ) ELSE lastx = lastxu 
  nx = lastx - firstxu + 1
; get e3t 3D
  e3t3d = e3t_3d(fstx = firstxu, lstx = lastx, fsty = firstyu, lsty = lastyu)
;
  IF keyword_set(key_partialstep) THEN BEGIN
;
; Rebuild the U-point 3D partial steps array from T-point 3D e3t_3D array 
;
    tmp = shift(e3t3d, -1, 0, 0)
    IF nx EQ nxu THEN BEGIN
      IF keyword_set(key_periodic) THEN BEGIN
        IF nx NE jpi THEN BEGIN
; get the values from i = 0
          tmp[nx-1, *, *] = e3t_3d(fstx = 0, lstx = 0, fsty = firstyu, lsty = lastyu)
        ENDIF
      ENDIF ELSE BEGIN
        tmp[nx-1, *, *] = e3t3d[nx-1, *, *]
      ENDELSE
    ENDIF
    e3u3d = [ [ (temporary(e3t3d))[*] ], [ (temporary(tmp))[*] ] ]
    e3u3d = min(temporary(e3u3d), dimension = 2)
    e3u3d = reform(e3u3d, nx, nyu, nzt, /overwrite)
;
    IF nx EQ nxu + 1 THEN e3u3d = (temporary(e3u3d))[0:nx-2, *, *]
;    
  ENDIF ELSE e3u3d = temporary(e3t3d)
;
  CASE 1 OF
    keyword_set(e1) AND keyword_set(e2):arr2d = e1u[firstxu:lastxu, firstyu:lastyu] $
                                              * e2u[firstxu:lastxu, firstyu:lastyu]
    keyword_set(e1)                    :arr2d = e1u[firstxu:lastxu, firstyu:lastyu]
                        keyword_set(e2):arr2d = e2u[firstxu:lastxu, firstyu:lastyu]
    ELSE:
  ENDCASE
;
  IF n_elements(arr2d) NE 0 THEN e3u3d = temporary(e3u3d) * ( arr2d[*] # replicate(1., nzt) )
;
  return, e3u3d
END