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PROGRAM PGDEM8
C
C From: Philip Palmer <philip@maths.qmw.ac.uk>
C Date: Mon, 26 Nov 90 12:27:22 GMT
C
C This program plots a 3d surface using PGSURF.
C
INTEGER NCURVE
PARAMETER(NCURVE=21)
INTEGER I,J, PGBEG
REAL A(NCURVE,NCURVE),XLIMS(3,2)
REAL AA1,AA2,AA3,AA4
REAL X,Y,DX,DY,THD,PHD,Q
REAL POT
COMMON/COEFS/AA1,AA2,AA3,AA4
C
THD=40.
PHD=-35.
Q=0.1
AA1=60./17.-24.*Q/17.
AA2=12./17.
AA3=52./17.
AA4=24./17.
XLIMS(1,1)=0.
XLIMS(1,2)=0.43
XLIMS(2,1)=-1.5
XLIMS(2,2)=1.5
XLIMS(3,1)=0.
XLIMS(3,2)=1.
DX=(XLIMS(1,2)-XLIMS(1,1))/(NCURVE-1)
DY=(XLIMS(2,2)-XLIMS(2,1))/(NCURVE-1)
DO 1 I=1,NCURVE
X=XLIMS(1,1)+(I-1)*DX
DO 2 J=1,NCURVE
Y=XLIMS(2,1)+(J-1)*DY
A(I,J)=POT(X,Y)
2 CONTINUE
1 CONTINUE
IF (PGBEG(0,'?',1,1) .NE. 1) STOP
CALL PGSURF(A,NCURVE,NCURVE,XLIMS,THD,PHD)
CALL PGEND
END
REAL FUNCTION POT(X,Y)
REAL X,Y
C
REAL X2,Y2,XX,YY
REAL AA1,AA2,AA3,AA4
COMMON/COEFS/AA1,AA2,AA3,AA4
C
Y2=Y*Y
X2=12.*X*X
XX=.5*(Y2+X2)
YY=Y2/3.+Y*X2
POT=1.-AA1*XX-AA2*YY+AA3*XX*XX+AA4*XX*YY
RETURN
END
SUBROUTINE PGSURF(A,NX,NY,XLIMS,THD,PHD)
INTEGER NX,NY
REAL A(NX,NY),XLIMS(3,2),THD,PHD
C
C This routine plots a 3d surface projected onto a 2D plane.
C The underside of the surface appears dotted or in blue, on
C clour terminals. This routine does the projection for you,
C you just need to specify the viewing direction in terms of
C spherical polar angles. As a result, this routine calls
C pgwind for you.
C
C Arguments:
C a (input) : data array, equally spaced in x and equally
C spaced in y, although steps in x and y may
C differ.
C nx (input) : dimension of data array in x direction.
C ny (input) : dimension of data array in y direction.
C xlims (input): array of min and max values in x, y and z
C respectively.
C thd (input) : viewing direction given as spherical theta angle
C in degrees. 0<= thd <= 90.
C phd (input) : viewing direction given as spherical phi angle
C in degrees. -180 <= phd <= 180.
C
INTEGER I,J,K,N,IFLAG,I0,I1,NSTART,NLINE,ISGN,JSGN
INTEGER IMAX,JMAX,K0,K1
REAL DTOR, TH,PH,CTH,STH,CPH,SPH
REAL XMIN,XMAX,YMIN,YMAX,ZMIN,ZMAX,Z1,Z2,Q1,Q2,Q3
REAL A1,A2,A3,A4,B1,B2,B3,B4,XSTART,YSTART
REAL XPMIN,XPMAX,YPMIN,YPMAX,DX,DY,ZZ,T
REAL XA(2),YA(2),ZA(2)
COMMON/PGSRF1/CTH,STH,CPH,SPH,NLINE,NSTART,IFLAG
C
IFLAG=0
CALL PGQCOL(I0,I1)
IF(I1.NE.1) IFLAG=1
CALL PGBBUF
DTOR=0.0174533
TH=THD*DTOR
PH=PHD*DTOR
CTH=COS(TH)
STH=SIN(TH)
CPH=COS(PH)
SPH=SIN(PH)
XMIN=XLIMS(1,1)
XMAX=XLIMS(1,2)
YMIN=XLIMS(2,1)
YMAX=XLIMS(2,2)
ZMIN=XLIMS(3,1)
ZMAX=XLIMS(3,2)
C
C Calculate plotting order from
C viewing orientation
C
Z1=ZMIN*STH
Z2=ZMAX*STH
IF(PHD.GT.0.) THEN
A1=-XMAX*SPH
A2=-XMIN*SPH
B3=-YMAX*SPH*CTH
B4=-YMIN*SPH*CTH
YSTART=YMAX
ISGN=-1
ELSE
A1=-XMIN*SPH
A2=-XMAX*SPH
B3=-YMIN*SPH*CTH
B4=-YMAX*SPH*CTH
YSTART=YMIN
ISGN=1
ENDIF
IF(ABS(PHD).LT.90.) THEN
B1=YMIN*CPH
B2=YMAX*CPH
A3=-XMAX*CPH*CTH
A4=-XMIN*CPH*CTH
XSTART=XMAX
JSGN=-1
ELSE
B1=YMAX*CPH
B2=YMIN*CPH
A3=-XMIN*CPH*CTH
A4=-XMAX*CPH*CTH
XSTART=XMIN
JSGN=1
ENDIF
XPMIN=MIN(A1,B1)
XPMAX=MAX(A2,B2)
YPMAX=MAX(A4,B4,Z2)
YPMIN=MIN(A3,B3,Z1)
CALL WINDOW(XPMIN,XPMAX,YPMIN,YPMAX)
C
C Draw coordinate axes
C
NSTART=0
NLINE=1
XA(1)=0.
XA(2)=0.
YA(1)=YMIN
YA(2)=YMAX
CALL PROJ(XA,YA,XA,1,1)
NLINE=1
YA(1)=XMIN
YA(2)=XMAX
CALL PROJ(YA,XA,XA,1,1)
NLINE=1
YA(1)=ZMIN
YA(2)=ZMAX
CALL PROJ(XA,XA,YA,1,1)
C
C Draw curves stepped in x
C
IMAX=NX-1
JMAX=NY-1
DX=JSGN*(XMAX-XMIN)/IMAX
DY=(YMAX-YMIN)/JMAX
Q1=DX*STH*SPH
Q2=DY*STH*CPH
Q3=DX*DY*CTH
IF(JSGN.EQ.1) THEN
K0=1
ELSE
K0=NX
ENDIF
DO 1 I=0,IMAX
NSTART=0
NLINE=1
XA(1)=XSTART+I*DX
XA(2)=XA(1)
K=K0+JSGN*I
DO 2 J=0,JMAX-1
YA(1)=YMIN+J*DY
YA(2)=YA(1)+DY
ZA(1)=A(K,J+1)
ZA(2)=A(K,J+2)
K1=K+JSGN
IF(K1.GE.1.AND.K1.LE.NX) THEN
ZZ=A(K1,J+1)
ELSE
K1=K-JSGN
ZZ=2.*ZA(1)-A(K1,J+1)
ENDIF
T=Q3-Q2*(ZZ-ZA(1))-Q1*(ZA(2)-ZA(1))
T=JSGN*T
IF(T.GT.0.) THEN
N=1+IFLAG
ELSE
N=4
ENDIF
CALL PROJ(XA,YA,ZA,N,NX)
2 CONTINUE
1 CONTINUE
C
C Draw curves stepped in y
C
DY=ISGN*DY
DX=JSGN*DX
Q1=JSGN*Q1
Q2=ISGN*Q2
Q3=ISGN*JSGN*Q3
IF(ISGN.EQ.1) THEN
K0=1
ELSE
K0=NY
ENDIF
DO 3 J=0,JMAX
NSTART=0
NLINE=1
YA(1)=YSTART+J*DY
YA(2)=YA(1)
K=K0+ISGN*J
DO 4 I=0,IMAX-1
XA(1)=XMIN+I*DX
XA(2)=XA(1)+DX
ZA(1)=A(I+1,K)
ZA(2)=A(I+2,K)
K1=K+ISGN
IF(K1.GE.1.AND.K1.LE.NY) THEN
ZZ=A(I+1,K1)
ELSE
K1=K-ISGN
ZZ=2.*ZA(1)-A(I+1,K1)
ENDIF
T=Q3-Q1*(ZZ-ZA(1))-Q2*(ZA(2)-ZA(1))
T=ISGN*T
IF(T.GT.0.) THEN
N=1+IFLAG
ELSE
N=4
ENDIF
CALL PROJ(XA,YA,ZA,N,NY)
4 CONTINUE
3 CONTINUE
CALL PGEBUF
RETURN
END
SUBROUTINE PROJ(X,Y,Z,N,NCURVE)
REAL X(2),Y(2),Z(2)
INTEGER N, NCURVE
C
REAL XP(100),YP(100)
REAL CTH,STH,CPH,SPH
INTEGER NLINE,NSTART,IFLAG,M
COMMON/PGSRF1/CTH,STH,CPH,SPH,NLINE,NSTART,IFLAG
SAVE M
IF(NLINE.EQ.1) THEN
XP(1)=Y(1)*CPH-X(1)*SPH
YP(1)=Z(1)*STH-(X(1)*CPH+Y(1)*SPH)*CTH
XP(2)=Y(2)*CPH-X(2)*SPH
YP(2)=Z(2)*STH-(X(2)*CPH+Y(2)*SPH)*CTH
IF(N.NE.M) THEN
M=N
IF(IFLAG.EQ.0) THEN
CALL PGSLS(N)
ELSE
CALL PGSCI(N)
ENDIF
ENDIF
NLINE=2
ELSE
IF(N.NE.M) THEN
CALL PGLINE(NLINE,XP,YP)
NSTART=NSTART+NLINE-1
M=N
IF(IFLAG.EQ.0) THEN
CALL PGSLS(N)
ELSE
CALL PGSCI(N)
ENDIF
XP(1)=XP(NLINE)
YP(1)=YP(NLINE)
NLINE=1
ENDIF
NLINE=NLINE+1
XP(NLINE)=Y(2)*CPH-X(2)*SPH
YP(NLINE)=Z(2)*STH-(X(2)*CPH+Y(2)*SPH)*CTH
ENDIF
IF(NLINE+NSTART.GE.NCURVE) CALL PGLINE(NLINE,XP,YP)
RETURN
END
SUBROUTINE WINDOW(XMIN,XMAX,YMIN,YMAX)
REAL XMIN, XMAX, YMIN, YMAX
C
C This subroutine sets up the standard pgwind, but with a
C cream background. It can be ported to any program.
C
CALL PGPAGE
CALL PGSCR(0,216/255.,216/255.,191/255.)
CALL PGERAS
CALL PGSWIN(XMIN,XMAX,YMIN,YMAX)
CALL PGSCI(1)
RETURN
END
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