SUBROUTINE	SCPLOT(X,Y,ISIZE)
C
C	THIS SUBROUTINE TAKES AN ARRAY OF X,Y COORDINATES OF SIZE=ISIZE
C	AND PLOTS THEM ON A TERMINAL WITH 1024 BY 780 RESOLUTION.
C	IF ISIZE < 0 THEN THE PLOT BEGINS WITH THE FIRST POINT.
C	IF ISIZE > 0 THEN THE PLOT CONTINUES WHERE THE LAST CALL TO SCPLOT
C	LEFT OFF.  IF THE LINES ARE OUTSIDE OF THE ACTIVE AREA THEY ARE CUT
C	SHORT.  SCALE FACTORS MAY BE ENTERED THROUGH 'PSSCAL'.
C
	REAL X(1),Y(1)
	INTEGER IX(60),IY(60)
	DATA XMAX / 1023.9/, YMAX / 779.9/	!MAX SCREEN SIZES
	DATA XO,YO,XSCAL,YSCAL/0.,0.,1.,1./	!INITIAL SCALE FACTORS
	ISIZ	= ISIZE
	IF(ISIZE .GT. 0)GO TO 50		!CONTINUE FROM OLD X,Y
	ISIZ	= - ISIZ
	X0	= (X(1) - XO)/XSCAL		!STARTING POINT OF PLOT X
	Y0	= (Y(1) - YO)/YSCAL		!Y STARTING POINT
	IF(ISIZ .LE. 1)RETURN			!IF NO VECT MERELY SAVE X0,Y0
50	IA	= 1
	DO 600 I	= 1,ISIZ
	X0SAV	= X0
	XSAV	= (X(I) - XO)/XSCAL		!SCALED X POSITION
	XT	= XSAV
	YSAV	= (Y(I) - YO)/YSCAL		!SCALED Y POSITION
	YT	= YSAV
C
C	TRUNCATE THE VECTORS
C
	IF(X0 .GT. XT)GO TO 100
	CALL XYTRNK(X0,XT,Y0,YT,XMAX,IGOOD)	!TRUNCATE X
	GO TO 200
100	CALL XYTRNK(XT,X0,YT,Y0,XMAX,IGOOD)	!TRUNCATE X
200	IF(IGOOD .EQ. 0)GO TO 420
	IF(Y0 .GT. YT)GO TO 300
	CALL XYTRNK(Y0,YT,X0,XT,YMAX,IGOOD)	!TRUNCATE Y
	GO TO 400
300	CALL XYTRNK(YT,Y0,XT,X0,YMAX,IGOOD)	!TRUNCATE Y
400	CONTINUE
	IF(IGOOD .EQ. 0)GO TO 420		!DO PLOT SINCE IT IS BROKEN LINE SEGMENT
	IF(IA .EQ. 10)  GO TO 420		!DO PLOT TO EMPTY BUFFER
	IF(X0 .EQ. X0SAV .AND. XT .EQ. X(I))GO TO 450	!NO CHANGES IN XY
420	IF(IA .GT.1 )CALL VECT(IX,IY,-IA)
	IA	= 1
	IF(IGOOD .EQ. 0)GO TO 500
450	CONTINUE
	IF(IA .GT. 1)GO TO 460			!DO NOT DO X0,Y0
	IX(1)	= X0				!SET UP FIRST POINT
	IY(1)	= Y0
460	IA	= IA + 1			!COUNT # OF POINTS TO PLOT
	IX(IA)	= XT
	IY(IA)	= YT
500	CONTINUE
	X0	= XSAV				!SAVE NEXT STARTING POINT
	Y0	= YSAV
600	CONTINUE
	IF(IA .GT. 1)CALL VECT(IX,IY,-IA)	!IF POINTS LEFT OVER PLOT THEM
	RETURN
C
C	HERE IS SEPARATE ENTRY TO DO SCALING
C
	ENTRY	PSSCAL(X1,X2,X3,X4)
C
C	CALL PSSCAL(X0,XSCAL,Y0,YSCAL)
C
C	X0	= OROGIN OF X COORDINATES
C	XSCAL	= # OF USER UNITS /SCREEN STEP
C			SCREEN STEP = .1" APPROXIMATELY
C
	XO	= X1
	XSCAL	= X2
	YO	= X3
	YSCAL	= X4
	IF(XSCAL .EQ. 0)XSCAL	= 1.		!PREVENT ZERO SCALE VALUES
	IF(YSCAL .EQ. 0)YSCAL	= 1.
	RETURN

	ENTRY SCTONE(X,Y,ISIZE)
C
C	SUBROUTINE TO PRODUCE SHADED PICTURE (SIMILAR TO VERSATEC TONE)
C
C	X,Y	= ARRAY OF COORDINATES FORMING A CLOSED POLYGON
C	ISIZE	= NUMBER OF POINTS
C
	CALL SCTEST(ITST,,,,,,MY,MX,MYRES,MXRES)
	IF(ITST .eq. 0) RETURN		! No plots possible
	MIN	= MX+1			!SET UP TO FIND MIN,MAX
	MAX	= 0
	DO 710 J	= 1,ISIZE		!SEARCH THRU ALL POINTS
	TEMP	= ( X(J) - XO )/XSCAL
	IF(TEMP .LT. 0.) TEMP	= 0.
	IF(TEMP .GT. MX) TEMP	= MX
	IF(TEMP .LT. MIN) MIN	= TEMP
	IF(TEMP .GT. MAX) MAX	= TEMP
710	CONTINUE
	LINE	= -1			! Current line number
	FAC	= FLOAT(MXRES)/(MX+1)	! Resolution
	DO 800 IXP = MIN,MAX		! SHADE OVER ALL VALUES
	XPT	= IXP
	JLINE	= XPT*FAC		! Current line number
	IF(JLINE .eq. LINE) Go to 800	! Current line already done ?
	ISZ	= 0			!WILL BE # OF SEGMENTS
	DO 780 J	= 1,ISIZE	!LOOK FOR HORIZ. BOUNDARIES
	K	= J - 1			!J,K DEFINE PT. # AT ENDS OF LINES
	IF(K .LT. 1) K	= ISIZE		!FIRST,LAST POINT JOIN
	XA	= ( X(K) - XO )/XSCAL
	XB	= ( X(J) - XO )/XSCAL
	IF(XPT .GE. XA .AND. XPT .LT. XB) GO TO 740
	IF(XPT .LT. XA .AND. XPT .GE. XB) GO TO 740
	GO TO 780			!NO HORIZONTAL SEGMENT FOUND, DONE
740	YB	= ( Y(J) - YO )/YSCAL
	YA	= ( Y(K) - YO )/YSCAL
	TEMP	= XB - XA
	IF(TEMP .EQ. 0.) GO TO 750
	TEMP	= (YB - YA)/TEMP
750	TEMP	= YA + (XPT - XA) * TEMP
	IF(TEMP .LT. 520) GO TO 751
751	CONTINUE
	IF(TEMP .LT. 0.)TEMP	= 0.	!MINIMUM Y VALUE IS 0
	IF(TEMP .GT. 779.)TEMP	= 779.	!MAXIMUM IS 779.
	ISZ	= ISZ + 1		!NUMBER OF BOUNDARIES FOUND
	IY(ISZ)	= TEMP			!Y BOUNDARIES
	IF(ISZ .GE. 50) GO TO 781	!DONE
780	X1	= X2
781	IF(ISZ .LE. 0) GO TO 800	!NO DATA TO PLOT
	DO 785	I	= 1,ISZ		!PUT Y VALUES INTO ASCENDING ORDER
	IX(I)	= IXP			!X VALUE CORRESPONDING TO Y
	DO 785	J	= I,ISZ
	IF(IY(J) .GE. IY(I)) GO TO 785	!IF LOWER INDEX VALUE NOT SMALLER
	K	= IY(J)			!SWAP THEM
	IY(J)	= IY(I)
	IY(I)	= K
785	CONTINUE
	DO 790 I	= 1,ISZ,2		!PLOT ALL SEGMENTS
	IY(I)	= - IY(I)			!START NEW VECTOR
790	CONTINUE
	CALL VECT(IX,IY,-ISZ)			!PLOT IT
800	LINE	= JLINE
	END

	SUBROUTINE	XYTRNK(X0,X,Y0,Y,AMAX,IGOOD)
C
C	SPECIAL SUBROUTINE TO TRUNCATE X VALUES OF VECTOR TO THE RANGE
C	0 TO AMAX.  X0 < X IS ASSUMED.
C
	IF(X0 .GT. AMAX)GO TO 500		!NO GOOD
	IF(X  .LT. 0.  )GO TO 500
	IF(X0 .GE. 0.  )GO TO 200		!X0 IS WITHIN RANGE
	IF(X - X0 .LE. 0.1)GO TO 500		!NO GOOD
	Y0	= Y0 - X0 * (Y-Y0) / (X-X0)	!NEW Y0
	X0	= 0.				!NEW X0 WITHIN RANGE
200	CONTINUE
	IF(X  .LE. AMAX)GO TO 400		!X IS AOK
	IF(X - X0 .LE. 0.1)GO TO 500		!DIFFERENCE TOO SMALL
	Y	= Y0 + (AMAX-X0) * (Y-Y0) / (X-X0)	!NEW Y VALUE
	X	= AMAX				!NEW X VALUE
400	IGOOD	= -1				!OK
	RETURN
500	IGOOD	= 0				!NOT GOOD
	END