--- ray/src/px/pinterp.c	1989/12/28 15:09:28	1.6
+++ ray/src/px/pinterp.c	1990/12/21 17:20:07	1.31
@@ -10,144 +10,220 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #include "standard.h"
 
+#include <fcntl.h>
+
 #include "view.h"
 
 #include "color.h"
 
-#define pscan(y)	(ourpict+(y)*ourview.hresolu)
-#define zscan(y)	(ourzbuf+(y)*ourview.hresolu)
+#ifndef BSD
+#define vfork		fork
+#endif
 
+#define pscan(y)	(ourpict+(y)*hresolu)
+#define zscan(y)	(ourzbuf+(y)*hresolu)
+
+#define F_FORE		1		/* fill foreground */
+#define F_BACK		2		/* fill background */
+
+#define PACKSIZ		42		/* calculation packet size */
+
+#define RTCOM		"rtrace -h -ovl -fff %s"
+
 #define ABS(x)		((x)>0?(x):-(x))
 
-VIEW	ourview = STDVIEW(512);		/* desired view */
+struct position {int x,y; float z;};
 
-double	zeps = 0.001;			/* allowed z epsilon */
+VIEW	ourview = STDVIEW;		/* desired view */
+int	hresolu = 512;			/* horizontal resolution */
+int	vresolu = 512;			/* vertical resolution */
+double	pixaspect = 1.0;		/* pixel aspect ratio */
 
+double	zeps = .02;			/* allowed z epsilon */
+
 COLR	*ourpict;			/* output picture */
 float	*ourzbuf;			/* corresponding z-buffer */
 
 char	*progname;
 
-VIEW	theirview = STDVIEW(512);	/* input view */
-int	gotview;			/* got input view? */
+int	fillo = F_FORE|F_BACK;		/* selected fill options */
+int	fillsamp = 0;			/* sample separation (0 == inf) */
+extern int	backfill(), rcalfill();	/* fill functions */
+int	(*fillfunc)() = backfill;	/* selected fill function */
+COLR	backcolr = BLKCOLR;		/* background color */
+double	backz = 0.0;			/* background z value */
+int	normdist = 1;			/* normalized distance? */
+double	ourexp = -1;			/* output picture exposure */
 
+VIEW	theirview = STDVIEW;		/* input view */
+int	gotview;			/* got input view? */
+int	thresolu, tvresolu;		/* input resolution */
+double	theirexp;			/* input picture exposure */
 double	theirs2ours[4][4];		/* transformation matrix */
+int	hasmatrix = 0;			/* has transformation matrix */
 
+int	childpid = -1;			/* id of fill process */
+FILE	*psend, *precv;			/* pipes to/from fill calculation */
+int	queue[PACKSIZ][2];		/* pending pixels */
+int	queuesiz;			/* number of pixels pending */
 
+
 main(argc, argv)			/* interpolate pictures */
 int	argc;
 char	*argv[];
 {
 #define check(olen,narg)	if (argv[i][olen] || narg >= argc-i) goto badopt
+	extern double	atof();
 	int	gotvfile = 0;
+	char	*zfile = NULL;
 	char	*err;
-	int	i;
+	int	i, rval;
 
 	progname = argv[0];
 
-	for (i = 1; i < argc && argv[i][0] == '-'; i++)
+	for (i = 1; i < argc && argv[i][0] == '-'; i++) {
+		rval = getviewopt(&ourview, argc-i, argv+i);
+		if (rval >= 0) {
+			i += rval;
+			continue;
+		}
 		switch (argv[i][1]) {
 		case 't':				/* threshold */
 			check(2,1);
 			zeps = atof(argv[++i]);
 			break;
-		case 'x':				/* x resolution */
-			check(2,1);
-			ourview.hresolu = atoi(argv[++i]);
+		case 'n':				/* dist. normalized? */
+			check(2,0);
+			normdist = !normdist;
 			break;
-		case 'y':				/* y resolution */
-			check(2,1);
-			ourview.vresolu = atoi(argv[++i]);
-			break;
-		case 'v':				/* view */
+		case 'f':				/* fill type */
 			switch (argv[i][2]) {
-			case 't':				/* type */
-				check(4,0);
-				ourview.type = argv[i][3];
+			case '0':				/* none */
+				check(3,0);
+				fillo = 0;
 				break;
-			case 'p':				/* point */
-				check(3,3);
-				ourview.vp[0] = atof(argv[++i]);
-				ourview.vp[1] = atof(argv[++i]);
-				ourview.vp[2] = atof(argv[++i]);
+			case 'f':				/* foreground */
+				check(3,0);
+				fillo = F_FORE;
 				break;
-			case 'd':				/* direction */
-				check(3,3);
-				ourview.vdir[0] = atof(argv[++i]);
-				ourview.vdir[1] = atof(argv[++i]);
-				ourview.vdir[2] = atof(argv[++i]);
+			case 'b':				/* background */
+				check(3,0);
+				fillo = F_BACK;
 				break;
-			case 'u':				/* up */
-				check(3,3);
-				ourview.vup[0] = atof(argv[++i]);
-				ourview.vup[1] = atof(argv[++i]);
-				ourview.vup[2] = atof(argv[++i]);
+			case 'a':				/* all */
+				check(3,0);
+				fillo = F_FORE|F_BACK;
 				break;
-			case 'h':				/* horizontal */
+			case 's':				/* sample */
 				check(3,1);
-				ourview.horiz = atof(argv[++i]);
+				fillsamp = atoi(argv[++i]);
 				break;
-			case 'v':				/* vertical */
+			case 'c':				/* color */
+				check(3,3);
+				fillfunc = backfill;
+				setcolr(backcolr, atof(argv[i+1]),
+					atof(argv[i+2]), atof(argv[i+3]));
+				i += 3;
+				break;
+			case 'z':				/* z value */
 				check(3,1);
-				ourview.vert = atof(argv[++i]);
+				fillfunc = backfill;
+				backz = atof(argv[++i]);
 				break;
-			case 'f':				/* file */
+			case 'r':				/* rtrace */
 				check(3,1);
-				gotvfile = viewfile(argv[++i], &ourview);
-				if (gotvfile < 0) {
-					perror(argv[i]);
-					exit(1);
-				} else if (gotvfile == 0) {
-					fprintf(stderr, "%s: bad view file\n",
-							argv[i]);
-					exit(1);
-				}
+				fillfunc = rcalfill;
+				calstart(RTCOM, argv[++i]);
 				break;
 			default:
 				goto badopt;
 			}
 			break;
+		case 'z':				/* z file */
+			check(2,1);
+			zfile = argv[++i];
+			break;
+		case 'x':				/* x resolution */
+			check(2,1);
+			hresolu = atoi(argv[++i]);
+			break;
+		case 'y':				/* y resolution */
+			check(2,1);
+			vresolu = atoi(argv[++i]);
+			break;
+		case 'p':				/* pixel aspect */
+			check(2,1);
+			pixaspect = atof(argv[++i]);
+			break;
+		case 'v':				/* view file */
+			if (argv[i][2] != 'f')
+				goto badopt;
+			check(3,1);
+			gotvfile = viewfile(argv[++i], &ourview, 0, 0);
+			if (gotvfile < 0) {
+				perror(argv[i]);
+				exit(1);
+			} else if (gotvfile == 0) {
+				fprintf(stderr, "%s: bad view file\n",
+						argv[i]);
+				exit(1);
+			}
+			break;
 		default:
 		badopt:
-			fprintf(stderr, "%s: unknown option '%s'\n",
+			fprintf(stderr, "%s: command line error at '%s'\n",
 					progname, argv[i]);
-			exit(1);
+			goto userr;
 		}
-						/* check arguments */
-	if (argc-i < 2 || (argc-i)%2) {
-		fprintf(stderr, "Usage: %s [view args] pfile zfile ..\n",
-				progname);
-		exit(1);
 	}
+						/* check arguments */
+	if ((argc-i)%2)
+		goto userr;
 						/* set view */
 	if (err = setview(&ourview)) {
 		fprintf(stderr, "%s: %s\n", progname, err);
 		exit(1);
 	}
+	normaspect(viewaspect(&ourview), &pixaspect, &hresolu, &vresolu);
 						/* allocate frame */
-	ourpict = (COLR *)calloc(ourview.hresolu*ourview.vresolu,sizeof(COLR));
-	ourzbuf = (float *)calloc(ourview.hresolu*ourview.vresolu,sizeof(float));
-	if (ourpict == NULL || ourzbuf == NULL) {
-		perror(progname);
-		exit(1);
-	}
+	ourpict = (COLR *)malloc(hresolu*vresolu*sizeof(COLR));
+	ourzbuf = (float *)calloc(hresolu*vresolu,sizeof(float));
+	if (ourpict == NULL || ourzbuf == NULL)
+		syserror();
 							/* get input */
 	for ( ; i < argc; i += 2)
 		addpicture(argv[i], argv[i+1]);
 							/* fill in spaces */
-	fillpicture();
+	if (fillo&F_BACK)
+		backpicture(fillfunc, fillsamp);
+	else
+		fillpicture(fillfunc);
+							/* close calculation */
+	caldone();
 							/* add to header */
 	printargs(argc, argv, stdout);
 	if (gotvfile) {
-		printf(VIEWSTR);
+		fputs(VIEWSTR, stdout);
 		fprintview(&ourview, stdout);
-		printf("\n");
+		putc('\n', stdout);
 	}
-	printf("\n");
-							/* write output */
+	if (pixaspect < .99 || pixaspect > 1.01)
+		fputaspect(pixaspect, stdout);
+	if (ourexp > 0 && (ourexp < .995 || ourexp > 1.005))
+		fputexpos(ourexp, stdout);
+	putc('\n', stdout);
+							/* write picture */
 	writepicture();
+							/* write z file */
+	if (zfile != NULL)
+		writedistance(zfile);
 
 	exit(0);
+userr:
+	fprintf(stderr,
+	"Usage: %s [view opts][-t eps][-z zout][-fT][-n] pfile zspec ..\n",
+			progname);
+	exit(1);
 #undef check
 }
 
@@ -155,78 +231,98 @@ char	*argv[];
 headline(s)				/* process header string */
 char	*s;
 {
-	static char	*altname[] = {"rview","rpict","pinterp",VIEWSTR,NULL};
+	static char	*altname[] = {VIEWSTR,"rpict","rview","pinterp",NULL};
 	register char	**an;
 
-	printf("\t%s", s);
+	putc('\t', stdout);
+	fputs(s, stdout);
 
+	if (isexpos(s)) {
+		theirexp *= exposval(s);
+		return;
+	}
 	for (an = altname; *an != NULL; an++)
 		if (!strncmp(*an, s, strlen(*an))) {
-			if (sscanview(&theirview, s+strlen(*an)) == 0)
+			if (sscanview(&theirview, s+strlen(*an)) > 0)
 				gotview++;
 			break;
 		}
 }
 
 
-addpicture(pfile, zfile)		/* add picture to output */
-char	*pfile, *zfile;
+addpicture(pfile, zspec)		/* add picture to output */
+char	*pfile, *zspec;
 {
-	FILE	*pfp, *zfp;
+	extern double	atof();
+	FILE	*pfp;
+	int	zfd;
+	char	*err;
 	COLR	*scanin;
 	float	*zin;
-	char	*err;
-	int	xres, yres;
+	struct position	*plast;
 	int	y;
-					/* open input files */
+					/* open picture file */
 	if ((pfp = fopen(pfile, "r")) == NULL) {
 		perror(pfile);
 		exit(1);
 	}
-	if ((zfp = fopen(zfile, "r")) == NULL) {
-		perror(zfile);
-		exit(1);
-	}
-					/* get header and view */
-	printf("%s:\n", pfile);
+					/* get header with exposure and view */
+	theirexp = 1.0;
 	gotview = 0;
+	printf("%s:\n", pfile);
 	getheader(pfp, headline);
-	if (!gotview || fgetresolu(&xres, &yres, pfp) != (YMAJOR|YDECR)) {
+	if (!gotview || fgetresolu(&thresolu, &tvresolu, pfp)
+			!= (YMAJOR|YDECR)) {
 		fprintf(stderr, "%s: picture view error\n", pfile);
 		exit(1);
 	}
-	theirview.hresolu = xres;
-	theirview.vresolu = yres;
+	if (ourexp <= 0)
+		ourexp = theirexp;
+	else if (ABS(theirexp-ourexp) > .01*ourexp)
+		fprintf(stderr, "%s: different exposure (warning)\n", pfile);
 	if (err = setview(&theirview)) {
 		fprintf(stderr, "%s: %s\n", pfile, err);
 		exit(1);
 	}
 					/* compute transformation */
-	pixform(theirs2ours, &theirview, &ourview);
+	hasmatrix = pixform(theirs2ours, &theirview, &ourview);
 					/* allocate scanlines */
-	scanin = (COLR *)malloc(xres*sizeof(COLR));
-	zin = (float *)malloc(xres*sizeof(float));
-	if (scanin == NULL || zin == NULL) {
-		perror(progname);
-		exit(1);
+	scanin = (COLR *)malloc(thresolu*sizeof(COLR));
+	zin = (float *)malloc(thresolu*sizeof(float));
+	plast = (struct position *)calloc(thresolu, sizeof(struct position));
+	if (scanin == NULL || zin == NULL || plast == NULL)
+		syserror();
+					/* get z specification or file */
+	if ((zfd = open(zspec, O_RDONLY)) == -1) {
+		double	zvalue;
+		register int	x;
+		if (!isfloat(zspec) || (zvalue = atof(zspec)) <= 0.0) {
+			perror(zspec);
+			exit(1);
+		}
+		for (x = 0; x < thresolu; x++)
+			zin[x] = zvalue;
 	}
 					/* load image */
-	for (y = yres-1; y >= 0; y--) {
-		if (freadcolrs(scanin, xres, pfp) < 0) {
+	for (y = tvresolu-1; y >= 0; y--) {
+		if (freadcolrs(scanin, thresolu, pfp) < 0) {
 			fprintf(stderr, "%s: read error\n", pfile);
 			exit(1);
 		}
-		if (fread(zin, sizeof(float), xres, zfp) < xres) {
-			fprintf(stderr, "%s: read error\n", zfile);
+		if (zfd != -1 && read(zfd,(char *)zin,thresolu*sizeof(float))
+				< thresolu*sizeof(float)) {
+			fprintf(stderr, "%s: read error\n", zspec);
 			exit(1);
 		}
-		addscanline(y, scanin, zin);
+		addscanline(y, scanin, zin, plast);
 	}
 					/* clean up */
 	free((char *)scanin);
 	free((char *)zin);
+	free((char *)plast);
 	fclose(pfp);
-	fclose(zfp);
+	if (zfd != -1)
+		close(zfd);
 }
 
 
@@ -236,13 +332,17 @@ register VIEW	*vw1, *vw2;
 {
 	double	m4t[4][4];
 
+	if (vw1->type != VT_PER && vw1->type != VT_PAR)
+		return(0);
+	if (vw2->type != VT_PER && vw2->type != VT_PAR)
+		return(0);
 	setident4(xfmat);
-	xfmat[0][0] = vw1->vhinc[0];
-	xfmat[0][1] = vw1->vhinc[1];
-	xfmat[0][2] = vw1->vhinc[2];
-	xfmat[1][0] = vw1->vvinc[0];
-	xfmat[1][1] = vw1->vvinc[1];
-	xfmat[1][2] = vw1->vvinc[2];
+	xfmat[0][0] = vw1->hvec[0];
+	xfmat[0][1] = vw1->hvec[1];
+	xfmat[0][2] = vw1->hvec[2];
+	xfmat[1][0] = vw1->vvec[0];
+	xfmat[1][1] = vw1->vvec[1];
+	xfmat[1][2] = vw1->vvec[2];
 	xfmat[2][0] = vw1->vdir[0];
 	xfmat[2][1] = vw1->vdir[1];
 	xfmat[2][2] = vw1->vdir[2];
@@ -250,115 +350,241 @@ register VIEW	*vw1, *vw2;
 	xfmat[3][1] = vw1->vp[1];
 	xfmat[3][2] = vw1->vp[2];
 	setident4(m4t);
-	m4t[0][0] = vw2->vhinc[0]/vw2->vhn2;
-	m4t[1][0] = vw2->vhinc[1]/vw2->vhn2;
-	m4t[2][0] = vw2->vhinc[2]/vw2->vhn2;
-	m4t[3][0] = -DOT(vw2->vp,vw2->vhinc)/vw2->vhn2;
-	m4t[0][1] = vw2->vvinc[0]/vw2->vvn2;
-	m4t[1][1] = vw2->vvinc[1]/vw2->vvn2;
-	m4t[2][1] = vw2->vvinc[2]/vw2->vvn2;
-	m4t[3][1] = -DOT(vw2->vp,vw2->vvinc)/vw2->vvn2;
+	m4t[0][0] = vw2->hvec[0]/vw2->hn2;
+	m4t[1][0] = vw2->hvec[1]/vw2->hn2;
+	m4t[2][0] = vw2->hvec[2]/vw2->hn2;
+	m4t[3][0] = -DOT(vw2->vp,vw2->hvec)/vw2->hn2;
+	m4t[0][1] = vw2->vvec[0]/vw2->vn2;
+	m4t[1][1] = vw2->vvec[1]/vw2->vn2;
+	m4t[2][1] = vw2->vvec[2]/vw2->vn2;
+	m4t[3][1] = -DOT(vw2->vp,vw2->vvec)/vw2->vn2;
 	m4t[0][2] = vw2->vdir[0];
 	m4t[1][2] = vw2->vdir[1];
 	m4t[2][2] = vw2->vdir[2];
 	m4t[3][2] = -DOT(vw2->vp,vw2->vdir);
 	multmat4(xfmat, xfmat, m4t);
+	return(1);
 }
 
 
-addscanline(y, pline, zline)		/* add scanline to output */
+addscanline(y, pline, zline, lasty)	/* add scanline to output */
 int	y;
 COLR	*pline;
 float	*zline;
+struct position	*lasty;		/* input/output */
 {
 	extern double	sqrt();
-	double	pos[3];
+	FVECT	pos;
+	struct position	lastx, newpos;
 	register int	x;
-	register int	xpos, ypos;
 
-	for (x = 0; x < theirview.hresolu; x++) {
-		pos[0] = x - .5*(theirview.hresolu-1);
-		pos[1] = y - .5*(theirview.vresolu-1);
+	lastx.z = 0;
+	for (x = thresolu-1; x >= 0; x--) {
+		pos[0] = (x+.5)/thresolu;
+		pos[1] = (y+.5)/tvresolu;
 		pos[2] = zline[x];
+		if (movepixel(pos) < 0) {
+			lasty[x].z = lastx.z = 0;	/* mark invalid */
+			continue;
+		}
+		newpos.x = pos[0] * hresolu;
+		newpos.y = pos[1] * vresolu;
+		newpos.z = zline[x];
+					/* add pixel to our image */
+		if (pos[0] >= 0 && newpos.x < hresolu
+				&& pos[1] >= 0 && newpos.y < vresolu) {
+			addpixel(&newpos, &lastx, &lasty[x], pline[x], pos[2]);
+			lasty[x].x = lastx.x = newpos.x;
+			lasty[x].y = lastx.y = newpos.y;
+			lasty[x].z = lastx.z = newpos.z;
+		} else
+			lasty[x].z = lastx.z = 0;	/* mark invalid */
+	}
+}
+
+
+addpixel(p0, p1, p2, pix, z)		/* fill in pixel parallelogram */
+struct position	*p0, *p1, *p2;
+COLR	pix;
+double	z;
+{
+	double	zt = 2.*zeps*p0->z;		/* threshold */
+	int	s1x, s1y, s2x, s2y;		/* step sizes */
+	int	l1, l2, c1, c2;			/* side lengths and counters */
+	int	p1isy;				/* p0p1 along y? */
+	int	x1, y1;				/* p1 position */
+	register int	x, y;			/* final position */
+
+					/* compute vector p0p1 */
+	if (fillo&F_FORE && ABS(p1->z-p0->z) <= zt) {
+		s1x = p1->x - p0->x;
+		s1y = p1->y - p0->y;
+		l1 = ABS(s1x);
+		if (p1isy = (ABS(s1y) > l1))
+			l1 = ABS(s1y);
+	} else {
+		l1 = s1x = s1y = 1;
+		p1isy = -1;
+	}
+					/* compute vector p0p2 */
+	if (fillo&F_FORE && ABS(p2->z-p0->z) <= zt) {
+		s2x = p2->x - p0->x;
+		s2y = p2->y - p0->y;
+		if (p1isy == 1)
+			l2 = ABS(s2x);
+		else {
+			l2 = ABS(s2y);
+			if (p1isy != 0 && ABS(s2x) > l2)
+				l2 = ABS(s2x);
+		}
+	} else
+		l2 = s2x = s2y = 1;
+					/* fill the parallelogram */
+	for (c1 = l1; c1-- > 0; ) {
+		x1 = p0->x + c1*s1x/l1;
+		y1 = p0->y + c1*s1y/l1;
+		for (c2 = l2; c2-- > 0; ) {
+			x = x1 + c2*s2x/l2;
+			if (x < 0 || x >= hresolu)
+				continue;
+			y = y1 + c2*s2y/l2;
+			if (y < 0 || y >= vresolu)
+				continue;
+			if (zscan(y)[x] <= 0 || zscan(y)[x]-z
+						> zeps*zscan(y)[x]) {
+				zscan(y)[x] = z;
+				copycolr(pscan(y)[x], pix);
+			}
+		}
+	}
+}
+
+
+movepixel(pos)				/* reposition image point */
+FVECT	pos;
+{
+	FVECT	pt, direc;
+	
+	if (hasmatrix) {
+		pos[0] += theirview.hoff - .5;
+		pos[1] += theirview.voff - .5;
 		if (theirview.type == VT_PER) {
-			pos[2] /= sqrt( 1.
-					+ pos[0]*pos[0]*theirview.vhn2
-					+ pos[1]*pos[1]*theirview.vvn2 );
+			if (normdist)	/* adjust for eye-ray distance */
+				pos[2] /= sqrt( 1.
+					+ pos[0]*pos[0]*theirview.hn2
+					+ pos[1]*pos[1]*theirview.vn2 );
 			pos[0] *= pos[2];
 			pos[1] *= pos[2];
 		}
 		multp3(pos, pos, theirs2ours);
-		if (pos[2] <= 0.0)
-			continue;
+		if (pos[2] <= 0)
+			return(-1);
 		if (ourview.type == VT_PER) {
 			pos[0] /= pos[2];
 			pos[1] /= pos[2];
 		}
-		pos[0] += .5*ourview.hresolu;
-		pos[1] += .5*ourview.vresolu;
-		if (pos[0] < 0 || pos[0] > ourview.hresolu
-				|| pos[1] < 0 || pos[1] > ourview.vresolu)
-			continue;
-					/* check current value at pos */
-		xpos = pos[0];
-		ypos = pos[1];
-		if (zscan(ypos)[xpos] <= 0.0
-				|| zscan(ypos)[xpos] - pos[2]
-					> zeps*zscan(ypos)[xpos]) {
-			zscan(ypos)[xpos] = pos[2];
-			copycolr(pscan(ypos)[xpos], pline[x]);
-		}
+		pos[0] += .5 - ourview.hoff;
+		pos[1] += .5 - ourview.voff;
+		return(0);
 	}
+	if (viewray(pt, direc, &theirview, pos[0], pos[1]) < 0)
+		return(-1);
+	pt[0] += direc[0]*pos[2];
+	pt[1] += direc[1]*pos[2];
+	pt[2] += direc[2]*pos[2];
+	viewpixel(&pos[0], &pos[1], &pos[2], &ourview, pt);
+	if (pos[2] <= 0)
+		return(-1);
+	return(0);
 }
 
 
-fillpicture()				/* fill in empty spaces */
+backpicture(fill, samp)			/* background fill algorithm */
+int	(*fill)();
+int	samp;
 {
 	int	*yback, xback;
 	int	y;
-	COLR	pfill;
 	register int	x, i;
 							/* get back buffer */
-	yback = (int *)malloc(ourview.hresolu*sizeof(int));
-	if (yback == NULL) {
-		perror(progname);
-		return;
-	}
-	for (x = 0; x < ourview.hresolu; x++)
+	yback = (int *)malloc(hresolu*sizeof(int));
+	if (yback == NULL)
+		syserror();
+	for (x = 0; x < hresolu; x++)
 		yback[x] = -2;
+	/*
+	 * Xback and yback are the pixel locations of suitable
+	 * background values in each direction.
+	 * A value of -2 means unassigned, and -1 means
+	 * that there is no suitable background in this direction.
+	 */
 							/* fill image */
-	for (y = 0; y < ourview.vresolu; y++) {
+	for (y = 0; y < vresolu; y++) {
 		xback = -2;
-		for (x = 0; x < ourview.hresolu; x++)
-			if (zscan(y)[x] <= 0.0) {	/* empty pixel */
+		for (x = 0; x < hresolu; x++)
+			if (zscan(y)[x] <= 0) {		/* empty pixel */
+				/*
+				 * First, find background from above or below.
+				 * (farthest assigned pixel)
+				 */
 				if (yback[x] == -2) {
-					for (i = y+1; i < ourview.vresolu; i++)
-						if (zscan(i)[x] > 0.0)
+					for (i = y+1; i < vresolu; i++)
+						if (zscan(i)[x] > 0)
 							break;
-					if (i < ourview.vresolu
+					if (i < vresolu
 				&& (y <= 0 || zscan(y-1)[x] < zscan(i)[x]))
 						yback[x] = i;
 					else
 						yback[x] = y-1;
 				}
+				/*
+				 * Next, find background from left or right.
+				 */
 				if (xback == -2) {
-					for (i = x+1; x < ourview.hresolu; i++)
-						if (zscan(y)[i] > 0.0)
+					for (i = x+1; i < hresolu; i++)
+						if (zscan(y)[i] > 0)
 							break;
-					if (i < ourview.hresolu
+					if (i < hresolu
 				&& (x <= 0 || zscan(y)[x-1] < zscan(y)[i]))
 						xback = i;
 					else
 						xback = x-1;
 				}
+				/*
+				 * If we have no background for this pixel,
+				 * use the given fill function.
+				 */
 				if (xback < 0 && yback[x] < 0)
-					continue;
-				if (yback[x] < 0 || ABS(x-xback) <= 1
+					goto fillit;
+				/*
+				 * Compare, and use the background that is
+				 * farther, unless one of them is next to us.
+				 * If the background is too distant, call
+				 * the fill function.
+				 */
+				if ( yback[x] < 0
+					|| (xback >= 0 && ABS(x-xback) <= 1)
 					|| ( ABS(y-yback[x]) > 1
-				&& zscan(yback[x])[x] < zscan(y)[xback] ))
+						&& zscan(yback[x])[x]
+						< zscan(y)[xback] ) ) {
+					if (samp > 0 && ABS(x-xback) >= samp)
+						goto fillit;
 					copycolr(pscan(y)[x],pscan(y)[xback]);
-				else
+					zscan(y)[x] = zscan(y)[xback];
+				} else {
+					if (samp > 0 && ABS(y-yback[x]) > samp)
+						goto fillit;
 					copycolr(pscan(y)[x],pscan(yback[x])[x]);
+					zscan(y)[x] = zscan(yback[x])[x];
+				}
+				continue;
+			fillit:
+				(*fill)(x,y);
+				if (fill == rcalfill) {		/* use it */
+					clearqueue();
+					xback = x;
+					yback[x] = y;
+				}
 			} else {				/* full pixel */
 				yback[x] = -2;
 				xback = -2;
@@ -368,14 +594,198 @@ fillpicture()				/* fill in empty spaces */
 }
 
 
+fillpicture(fill)		/* paint in empty pixels using fill */
+int	(*fill)();
+{
+	register int	x, y;
+
+	for (y = 0; y < vresolu; y++)
+		for (x = 0; x < hresolu; x++)
+			if (zscan(y)[x] <= 0)
+				(*fill)(x,y);
+}
+
+
 writepicture()				/* write out picture */
 {
 	int	y;
 
-	fputresolu(YMAJOR|YDECR, ourview.hresolu, ourview.vresolu, stdout);
-	for (y = ourview.vresolu-1; y >= 0; y--)
-		if (fwritecolrs(pscan(y), ourview.hresolu, stdout) < 0) {
-			perror(progname);
+	fputresolu(YMAJOR|YDECR, hresolu, vresolu, stdout);
+	for (y = vresolu-1; y >= 0; y--)
+		if (fwritecolrs(pscan(y), hresolu, stdout) < 0)
+			syserror();
+}
+
+
+writedistance(fname)			/* write out z file */
+char	*fname;
+{
+	extern double	sqrt();
+	int	donorm = normdist && ourview.type == VT_PER;
+	int	fd;
+	int	y;
+	float	*zout;
+
+	if ((fd = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) == -1) {
+		perror(fname);
+		exit(1);
+	}
+	if (donorm
+	&& (zout = (float *)malloc(hresolu*sizeof(float))) == NULL)
+		syserror();
+	for (y = vresolu-1; y >= 0; y--) {
+		if (donorm) {
+			double	vx, yzn2;
+			register int	x;
+			yzn2 = (y+.5)/vresolu + ourview.voff - .5;
+			yzn2 = 1. + yzn2*yzn2*ourview.vn2;
+			for (x = 0; x < hresolu; x++) {
+				vx = (x+.5)/hresolu + ourview.hoff - .5;
+				zout[x] = zscan(y)[x]
+					* sqrt(vx*vx*ourview.hn2 + yzn2);
+			}
+		} else
+			zout = zscan(y);
+		if (write(fd, (char *)zout, hresolu*sizeof(float))
+				< hresolu*sizeof(float)) {
+			perror(fname);
 			exit(1);
 		}
+	}
+	if (donorm)
+		free((char *)zout);
+	close(fd);
+}
+
+
+isfloat(s)				/* see if string is floating number */
+register char	*s;
+{
+	for ( ; *s; s++)
+		if ((*s < '0' || *s > '9') && *s != '.' && *s != '-'
+				&& *s != 'e' && *s != 'E' && *s != '+')
+			return(0);
+	return(1);
+}
+
+
+backfill(x, y)				/* fill pixel with background */
+int	x, y;
+{
+	register BYTE	*dest = pscan(y)[x];
+
+	copycolr(dest, backcolr);
+	zscan(y)[x] = backz;
+}
+
+
+calstart(prog, args)			/* start fill calculation */
+char	*prog, *args;
+{
+	char	combuf[512];
+	int	p0[2], p1[2];
+
+	if (childpid != -1) {
+		fprintf(stderr, "%s: too many calculations\n", progname);
+		exit(1);
+	}
+	sprintf(combuf, prog, args);
+	if (pipe(p0) < 0 || pipe(p1) < 0)
+		syserror();
+	if ((childpid = vfork()) == 0) {	/* fork calculation */
+		close(p0[1]);
+		close(p1[0]);
+		if (p0[0] != 0) {
+			dup2(p0[0], 0);
+			close(p0[0]);
+		}
+		if (p1[1] != 1) {
+			dup2(p1[1], 1);
+			close(p1[1]);
+		}
+		execl("/bin/sh", "sh", "-c", combuf, 0);
+		perror("/bin/sh");
+		_exit(127);
+	}
+	if (childpid == -1)
+		syserror();
+	close(p0[0]);
+	close(p1[1]);
+	if ((psend = fdopen(p0[1], "w")) == NULL)
+		syserror();
+	if ((precv = fdopen(p1[0], "r")) == NULL)
+		syserror();
+	queuesiz = 0;
+}
+
+
+caldone()				/* done with calculation */
+{
+	int	pid;
+
+	if (childpid == -1)
+		return;
+	clearqueue();
+	fclose(psend);
+	fclose(precv);
+	while ((pid = wait(0)) != -1 && pid != childpid)
+		;
+	childpid = -1;
+}
+
+
+rcalfill(x, y)				/* fill with ray-calculated pixel */
+int	x, y;
+{
+	if (queuesiz >= PACKSIZ)	/* flush queue if needed */
+		clearqueue();
+					/* add position to queue */
+	queue[queuesiz][0] = x;
+	queue[queuesiz][1] = y;
+	queuesiz++;
+}
+
+
+clearqueue()				/* process queue */
+{
+	FVECT	orig, dir;
+	float	fbuf[6];
+	register int	i;
+
+	for (i = 0; i < queuesiz; i++) {
+		viewray(orig, dir, &ourview,
+				(queue[i][0]+.5)/hresolu,
+				(queue[i][1]+.5)/vresolu);
+		fbuf[0] = orig[0]; fbuf[1] = orig[1]; fbuf[2] = orig[2];
+		fbuf[3] = dir[0]; fbuf[4] = dir[1]; fbuf[5] = dir[2];
+		fwrite((char *)fbuf, sizeof(float), 6, psend);
+	}
+					/* flush output and get results */
+	fbuf[3] = fbuf[4] = fbuf[5] = 0.0;		/* mark */
+	fwrite((char *)fbuf, sizeof(float), 6, psend);
+	if (fflush(psend) == EOF)
+		syserror();
+	for (i = 0; i < queuesiz; i++) {
+		if (fread((char *)fbuf, sizeof(float), 4, precv) < 4) {
+			fprintf(stderr, "%s: read error in clearqueue\n",
+					progname);
+			exit(1);
+		}
+		if (ourexp > 0 && ourexp != 1.0) {
+			fbuf[0] *= ourexp;
+			fbuf[1] *= ourexp;
+			fbuf[2] *= ourexp;
+		}
+		setcolr(pscan(queue[i][1])[queue[i][0]],
+				fbuf[0], fbuf[1], fbuf[2]);
+		zscan(queue[i][1])[queue[i][0]] = fbuf[3];
+	}
+	queuesiz = 0;
+}
+
+
+syserror()			/* report error and exit */
+{
+	perror(progname);
+	exit(1);
 }