SUBROUTINE CLIP(VECT,ISTAT) C C NAME: CLIP C C LANGUAGE: FORTRAN C C OPERATING SYSTEM: UNIVERSAL C C ORDER NUMBER: 5428-SE C C PART NUMBER: 000-026366 NOVEMBER 1985 C C PRODUCT: UNIVERSAL VERSAPLOT COLOR RANDOM 2.0 C C VERSATEC, INC., SANTA CLARA, CALIFORNIA 95051 C A XEROX COMPANY C C Copyright (C) 1985 by Xerox Corporation. All rights reserved. C C "NOTICE. THIS PROGRAM IS THE EXCLUSIVE PROPERTY OF VERSATEC, C INC. AND IS ISSUED IN STRICT CONFIDENCE UNDER A PREARRANGED C LICENSE AGREEMENT AND IS NOT TO BE DISCLOSED IN ANY MANNER TO C PERSONS OUTSIDE THE LICENSED ORGANIZATION AND SHALL NOT BE C REPRODUCED OR DISSEMINATED, IN WHOLE OR PART, TO ANYONE OUTSIDE C THE LICENSED ORGANIZATION WITHOUT THE PRIOR WRITTEN APPROVAL OF C VERSATEC, INC. UNLESS OTHERWISE PROVIDED FOR BY SUCH LICENSE C AGREEMENT. THIS WORK IS PROTECTED AS AN UNPUBLISHED WORK UNDER C THE COPYRIGHT ACT OF 1976." C C CLIP - CLIP VECTOR TO SPECIFIED WINDOW C C CLIP IS PASSED A VECTOR AND RETURNS THE CLIPPED VECTOR AND C THE STATUS OF THE VECTOR IN RELATION TO THE CLIPPING WINDOW. C C THE CLIPPING ALGORITHM USED IS DESCRIBED IN DETAIL IN C SECTION 5-1 OF "PRINCIPLES OF INTERACTIVE COMPUTER GRAPHICS", C 2ND EDITION,NEWMAN AND SPROULL,MCGRAW HILL,1979. C C ENTRY: CALL CLIP(VECT,ISTAT) C C VECT() - A REAL ARRAY OF VECTOR COORDINATES: C VECT(1) - X1 C VECT(2) - Y1 C VECT(3) - X2 C VECT(4) - Y2 C ISTAT - CLIPPING STATUS RETURN C C EXIT: C ISTAT CONTAINS THE CLIPPING STATUS OF THE VECTOR. C IF ISTAT .EQ. 4 THEN C VECT WAS COMPLETELY OUTSIDE THE CLIPPING LIMITS C VECT REMAINS UNCHANGED C ELSE IF ISTAT .EQ. 0 THEN C VECT WAS COMPLETELY INSIDE THE CLIPPING LIMITS C VECT REMAINS UNCHANGED C ELSE IF ISTAT .EQ. 1 THEN C X1,Y1 LAY OUTSIDE THE CLIPPING LIMITS C VECT CONTAINS THE CLIPPED VECTOR C ELSE IF ISTAT .EQ. 2 THEN C X2,Y2 LAY OUTSIDE THE CLIPPING LIMITS C VECT CONTAINS THE CLIPPED VECTOR C ELSE IF ISTAT .EQ. 3 THEN C BOTH ENDPOINTS LAY OUTSIDE THE CLIPPING LIMITS C VECT CONTAINS THE CLIPPED VECTOR C C CALLS: OCODE,AND,OR C C CALLED BY: PLOT C C COMMON USED: C /DVCOM/ C R WIN() - THE CURRENT VIEW WINDOW IN COMPUTATIONAL C COORDINATES C /VRFCOM/ C I IOCODE()- THE OUTCODES FOR THE STARTING AND C ENDING POINTS OF A VECTOR C C LOCAL: C I IC - OUT CODE OF THE VECTOR ENDPOINT BEING PROCESSED C R X - X INTERSECTION OF THE VECTOR WITH WINDOW EDGE C R X1 - X ORDINATE OF THE FIRST VECTOR ENDPOINT C R X2 - X ORDINATE OF THE SECOND VECTOR ENDPOINT C R Y - Y INTERSECTION OF THE VECTOR WITH WINDOW EDGE C R Y1 - Y ORDINATE OF THE FIRST VECTOR ENDPOINT C R Y2 - Y ORDINATE OF THE SECOND VECTOR ENDPOINT C C C C LOGICAL ROT90,PMOVE,IPDEF,DASHPN,XMAJOR,VSFLAG INTEGER PWIDTH,XNIPS,YNIPS,PENPAT,VSMAX,PFONT C... COMMON /DVCOM/ PHASE I COMMON VARIABLES C COMMON /DVCOM/ * ANC, DASHPN, FACT, HTC, ICUT, ICWTV, ICXPTS, * IEOJ, ILWM, ILWP, IOPEN, ISORT, ITFLAG, IX1, * IX2, IY1, IY2, JFONT, JPEN, KPAT, KWIDTH, * LASTX, LASTY, MAXPAT, MSB, MSKALL, NCH, NCLIP, * NIBSX, NLPAT, NPLOT, PFONT, PMOVE, PXMIN, PXMAX, * PYMIN, PYMAX, RADN, ROT90, SXC, SYC, TSINA, * TCOSA, XDEN, XFAC, XNIPS, XOFF, YDEN, YFAC, * YOFF, YNIPS, VSFLAG, VSMAX, XMAJOR, * IPAT(16,256), IEOP(4), IHBUF(2), IPDEF(64), * NPAT(255), PENPAT(4,64), PWIDTH(64), * RORG(2), VCP(2), VP(4), WIN(4), WTV(4), WX(4), WY(4), * IAUTXT(15) C C C C... COMMON /VRFCOM/ - VRF COMMON VARIABLES C INTEGER PRECIS INTEGER OBUF COMMON /VRFCOM/ * DRWELM, DRWMAX, DRWMIN, DRWKNT, ICOPY, * ICNSTX, IBXMAX, IHDCNT, MIN, * NBYTS, NCHUNK, NHEAD, NREC, PRECIS, * RMXELM, VRFMAX, * BYTKNT(4), IBEGIN(4), ICOMD(2), IOCODE(2), IREC(4), * MAX(4), NEXTO(4), OBJKNT(4), VRFKNT(4), OBUF(640) C DIMENSION VECT(1) C C C... STORE WORKING VECTOR X1 = VECT(1) Y1 = VECT(2) X2 = VECT(3) Y2 = VECT(4) C ISTAT = 0 C C... REPEAT UNTIL WORKING VECTOR IS COMPLETELY INSIDE WINDOW C AN OUT CODE OF 0 MEANS THAT A POINT IS INSIDE THE CLIPPING C WINDOW WHEN BOTH ENDPOINTS OF A VECTOR LIE INSIDE THE WINDOW, C THE ENTIRE VECTOR LIES INSIDE THE WINDOW. 100 IF (IOCODE(1).EQ.0 .AND. IOCODE(2).EQ.0) GO TO 990 C C... IS WORKING VECTOR COMPLETELY OUTSIDE WINDOW? IF (AND(IOCODE(1),IOCODE(2)) .EQ. 0) GO TO 110 C C... YES. SET STATUS AND RETURN C IF THE VECTOR IS COMPLETELY OUTSIDE THE WINDOW, INDICATE C THIS BY SETTING THE STATUS FLAG. THE VECTOR RETURNED C IS THE VECTOR PASSED. ISTAT = 4 GO TO 999 C C... SET UP TO CLIP THE 1ST VECTOR ENDPOINT 110 IC = IOCODE(1) C C... IF THE 1ST ENDPOINT LIES INSIDE THE CLIPPING WINDOW, CLIP THE C... 2ND ENDPOINT IF (IC .EQ. 0) IC = IOCODE(2) C C C... FIND INTERSECTION WITH CLIPPING EDGE C THE INTERSECTION EQUATIONS ARE DERIVED FROM THE TWO POINT C EQUATION FOR A LINE: C Y-Y1 = (X-X1) * (Y2-Y1)/(X2-X1) C IF (AND(IC,1) .EQ.0) GO TO 120 C C... VECTOR CROSSES LEFT WINDOW EDGE. CLIP C THE Y INTERSECTION EQUATION BELOW IS DERIVED BY SOLVING C THE TWO POINT EQUATION FOR A LINE FOR X=WIN(XMIN). Y = Y1 + (WIN(1)-X1)*(Y2-Y1)/(X2-X1) X = WIN(1) GO TO 200 C 120 IF (AND(IC,2) .EQ.0) GO TO 130 C C... VECTOR CROSSES RIGHT WINDOW EDGE. CLIP C THE Y INTERSECTION EQUATION BELOW IS DERIVED BY SOLVING C THE TWO POINT EQUATION FOR A LINE FOR X=WIN(XMAX) Y = Y1 + (WIN(3)-X1)*(Y2-Y1)/(X2-X1) X = WIN(3) GO TO 200 C 130 IF (AND(IC,4) .EQ.0) GO TO 140 C C... VECTOR CROSSES BOTTOM WINDOW EDGE. CLIP C THE X INTERSECTION EQUATION BELOW IS DERIVED BY SOLVING C THE TWO POINT EQUATION FOR A LINE FOR Y=WIN(YMIN) X = X1 + (WIN(2)-Y1)*(X2-X1)/(Y2-Y1) Y = WIN(2) GO TO 200 C 140 IF (AND(IC,8) .NE.0) GO TO 145 C-E C... THIS ERROR SHOULD NEVER HAPPEN IN NORMAL OPERATION. C INVALID OUT CODE WAS PASSED. CALL MSGLG1(6) STOP C-E C C... VECTOR CROSSES TOP WINDOW EDGE. CLIP C THE X INTERSECTION EQUATION BELOW IS DERIVED BY SOLVING C THE TWO POINT EQUATION FOR A LINE FOR Y=WIN(YMAX) 145 X = X1 + (WIN(4)-Y1)*(X2-X1)/(Y2-Y1) Y = WIN(4) C C C... DETERMINE WHICH ENDPOINT WAS CLIPPED C THE OUT CODE OF THE CURRENT POINT IS COMPARED WITH THE OUT C CODE FOR THE FIRST ENDPOINT TO DETERMINE WHICH ENDPOINT HAS C BEEN CLIPPED. IF THE TWO CODES ARE EQUAL THE 1ST ENDPOINT C WAS CLIPPED. IF THEY AREN'T EQUAL, THEN THE 1ST ENDPOINT IS C INSIDE THE CLIPPING WINDOW AND IOCODE(1)=0. IN THIS CASE C THE 2ND END- POINT MUST HAVE BEEN CLIPPED. 200 IF (IC .NE. IOCODE(1)) GO TO 210 C C... X1,Y1 WAS CLIPPED X1 = X Y1 = Y C C... COMPUTE OUT CODE FOR CLIPPED ENDPOINT AND INDICATE THAT C THE 1ST ENDPOINT HAS BEEN CLIPPED IN THE STATUS RETURN CALL OCODE(X1,Y1,IOCODE(1)) ISTAT = OR(ISTAT,1) C C... CONTINUE REPEAT LOOP GO TO 100 C C... X2,Y2 WAS CLIPPED 210 X2 = X Y2 = Y C C... COMPUTE OUT CODE FOR CLIPPED ENDPOINT AND INDICATE THAT C THE 2ND ENDPOINT HAS BEEN CLIPPED IN THE STATUS RETURN CALL OCODE(X2,Y2,IOCODE(2)) ISTAT = OR(ISTAT,2) C C... CONTINUE REPEAT LOOP GO TO 100 C C C... RETURN THE CLIPPED VECTOR 990 VECT(1) = X1 VECT(2) = Y1 VECT(3) = X2 VECT(4) = Y2 C 999 RETURN END