# Example 6 -- interpolated surface

Please note that to compile the graphics portion of the code below, you must link with a double precision version of NCAR Graphics, or else you need to convert the code back to single precision before you call the graphics routines.

```      PROGRAM FTEX06
C
C  Example of SURF1DP/SURF2DP.
C
C
C Define error file, Fortran unit number, and workstation type,
C and workstation ID.
C
PARAMETER (IERRF=6,LUNIT=2,IWTYPE=1,IWKID=1)
C
PARAMETER (NXI=11,NYI=17,NXO=31,NYO=21,IDTEMP=2*NYI+NXI)
DOUBLE PRECISION X
DOUBLE PRECISION Y
DOUBLE PRECISION Z
DOUBLE PRECISION ZX1
DOUBLE PRECISION ZXM
DOUBLE PRECISION ZY1
DOUBLE PRECISION ZYN
DOUBLE PRECISION ZP
DOUBLE PRECISION TEMP
DOUBLE PRECISION XO
DOUBLE PRECISION YO
DOUBLE PRECISION ZO
DOUBLE PRECISION ZF
DOUBLE PRECISION U
DOUBLE PRECISION V
DOUBLE PRECISION SIGMA
DOUBLE PRECISION ZXY11
DOUBLE PRECISION ZXYM1
DOUBLE PRECISION ZXY1N
DOUBLE PRECISION ZXYMN
DOUBLE PRECISION TINCX
DOUBLE PRECISION TINCY
DOUBLE PRECISION SURF2DP
C
DIMENSION X(NXI),Y(NYI),Z(NXI,NYI)
DIMENSION ZX1(NYI),ZXM(NYI),ZY1(NXI),ZYN(NXI)
DIMENSION ZP(NXI,NYI,3),TEMP(IDTEMP)
DIMENSION XO(NXO),YO(NYO),ZO(NXO,NYO)
C
C Declare a function ZF(U,V) that defines a surface.
C
ZF(U,V) = .5D0 + .25D0*SIN(-7.D0*U) + .25D0*COS(5.D0*V)
C
C Define the surface to be drawn.
C
DO 104 I = 1,NXI
X(I) = DBLE(I-1)/DBLE(NXI-1)
DO 103 J = 1,NYI
Y(J) = DBLE(J-1)/DBLE(NYI-1)
Z(I,J) = ZF(X(I),Y(J))
103     CONTINUE
104 CONTINUE
C
C  Do SURF1DP set up.
C
SIGMA = 1.D0
ISF = 255
CALL SURF1DP(NXI,NYI,X,Y,Z,NXI,ZX1,ZXM,ZY1,ZYN,ZXY11,ZXYM1,ZXY1N,
+             ZXYMN,ISF,ZP,TEMP,SIGMA,IERR)
IF (IERR.NE.0) THEN
PRINT *,'Error return from SURF =',IERR
STOP
END IF
C
C  Get interpolated points using SURF2DP.
C
TINCX = 1.0D0/ (NXO-1)
TINCY = 1.0D0/ (NYO-1)
DO 20 I = 1,NXO
XO(I) = (I-1)*TINCX
DO 10 J = 1,NYO
YO(J) = (J-1)*TINCY
ZO(I,J) = SURF2DP(XO(I),YO(J),NXI,NYI,X,Y,Z,NXI,ZP,SIGMA)
10     CONTINUE
20 CONTINUE
C
C  Plot a surface.
C
CALL GOPKS(IERRF,ISZDM)
CALL GOPWK(IWKID,LUNIT,IWTYPE)
CALL GACWK(IWKID)
CALL TDEZ2D(NXO,NYO,XO,YO,ZO,3.D0,36.D0,67.D0,-6)
CALL FRAME
CALL GDAWK(IWKID)
CALL GCLWK(IWKID)
CALL GCLKS
C
STOP
END
```

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