begin

;
; Create some dummy data for the surface plot.
;
  NX = 21
  NY = 21
  NZ = 21

  xi = (/0.055483, 0.138127, 0.808924,-1.501205,-0.891079, 0.141545,\
         1.068575,-1.392315,-0.612384,-0.395337, 1.726188, 0.698080,\
        -0.443068, 1.307718, 1.916745, 1.833857, 1.120456,-1.887692,\
        -1.028046, 1.824213,-0.2324901/)

  yi = (/-1.297098, 1.790521,-1.094333,-1.664418,-0.527787, 1.062716,\
          1.120945, 0.501907, 1.668813, 0.427076, 1.479720, 1.033662,\
         -0.577471,-0.336375,-1.494247, 0.949919, 1.031587,-0.725059,\
          0.358226,-0.723472, 1.660146/)

  zi = (/-0.765465,-1.313089,-0.020937,-0.441481, 1.933836, 0.585894,\
          1.291848,-0.741295, 0.079043, 1.141697, 1.466170, 0.327586,\
         -1.199072,-0.145940,-1.149510,-0.363842, 1.827387, 1.027802,\
         -1.826411,-1.762566, 0.289010/) 

  wi = xi*xi + yi*yi + zi*zi

;
; Create the output grid.
;
  xmin = -2.0
  ymin = -2.0
  zmin = -2.0
  xmax =  2.0
  ymax =  2.0
  zmax =  2.0
  ii = fspan(0,20.,21)
  xo = xmin + (ii/(NX-1)) * (xmax-xmin)
  yo = ymin + (ii/(NY-1)) * (ymax-ymin)
  zo = zmin + (ii/(NZ-1)) * (zmax-zmin)

;
; Interpolate.
;
  wo = dsgrid3s(xi, yi, zi, wi, xo, yo, zo)

;
; Create an X workstation.
;
  wid = create "wks" ncgmWorkstationClass defaultapp end create

;
; Retrieve the GKS workstation id, which is necessary in order to
; interact with low-level libraries.
;
  getvalues wid
    "wkGksWorkId" : gkswid
  end getvalues

;
; Call tdez3d to draw a 3D plot.
;
  tdez3d(gkswid,xo,yo,zo,wo,3.,2.,-35.,65.,6)

  frame(wid) ; Advance the frame.
end