text: #ifndef lint
  static const char RCSid[] = "$Id: rpict.c,v 2.90 2015/04/22 20:28:16 rschregle Exp $";
  #endif
  /*
   *  rpict.c - routines and variables for picture generation.
   */
  
  #include "copyright.h"
  
  #include  <sys/types.h>
  
  #include  "platform.h"
  #ifdef NON_POSIX
   #ifdef MINGW
    #include  <sys/time.h>
   #endif
  #else
   #ifdef BSD
    #include  <sys/time.h>
    #include  <sys/resource.h>
   #else
    #include  <sys/times.h>
    #include  <unistd.h>
   #endif
  #endif
  
  #include  <time.h>
  #include  <signal.h>
  
  #include  "ray.h"
  #include  "paths.h"
  #include  "ambient.h"
  #include  "view.h"
  #include  "random.h"
  #include  "paths.h"
  #include  "hilbert.h"
  #include  "pmapbias.h"
  #include  "pmapdiag.h"
  
  #define	 RFTEMPLATE	"rfXXXXXX"
  
  #ifndef SIGCONT
  #ifdef SIGIO     /* XXX can we live without this? */
  #define SIGCONT		SIGIO
  #endif
  #endif
  
  CUBE  thescene;				/* our scene */
  OBJECT	nsceneobjs;			/* number of objects in our scene */
  
  int  dimlist[MAXDIM];			/* sampling dimensions */
  int  ndims = 0;				/* number of sampling dimensions */
  int  samplendx;				/* sample index number */
  
  void  (*addobjnotify[])() = {ambnotify, NULL};
  
  VIEW  ourview = STDVIEW;		/* view parameters */
  int  hresolu = 512;			/* horizontal resolution */
  int  vresolu = 512;			/* vertical resolution */
  double	pixaspect = 1.0;		/* pixel aspect ratio */
  
  int  psample = 4;			/* pixel sample size */
  double	maxdiff = .05;			/* max. difference for interpolation */
  double	dstrpix = 0.67;			/* square pixel distribution */
  
  double  mblur = 0.;			/* motion blur parameter */
  
  double  dblur = 0.;			/* depth-of-field blur parameter */
  
  void  (*trace)() = NULL;		/* trace call */
  
  int  do_irrad = 0;			/* compute irradiance? */
  
  int  rand_samp = 0;			/* pure Monte Carlo sampling? */
  
  double	dstrsrc = 0.0;			/* square source distribution */
  double	shadthresh = .05;		/* shadow threshold */
  double	shadcert = .5;			/* shadow certainty */
  int  directrelay = 1;			/* number of source relays */
  int  vspretest = 512;			/* virtual source pretest density */
  int  directvis = 1;			/* sources visible? */
  double	srcsizerat = .25;		/* maximum ratio source size/dist. */
  
  COLOR  cextinction = BLKCOLOR;		/* global extinction coefficient */
  COLOR  salbedo = BLKCOLOR;		/* global scattering albedo */
  double  seccg = 0.;			/* global scattering eccentricity */
  double  ssampdist = 0.;			/* scatter sampling distance */
  
  double	specthresh = .15;		/* specular sampling threshold */
  double	specjitter = 1.;		/* specular sampling jitter */
  
  int  backvis = 1;			/* back face visibility */
  
  int  maxdepth = 7;			/* maximum recursion depth */
  double	minweight = 1e-3;		/* minimum ray weight */
  
  char  *ambfile = NULL;			/* ambient file name */
  COLOR  ambval = BLKCOLOR;		/* ambient value */
  int  ambvwt = 0;			/* initial weight for ambient value */
  double	ambacc = 0.2;			/* ambient accuracy */
  int  ambres = 64;			/* ambient resolution */
  int  ambdiv = 512;			/* ambient divisions */
  int  ambssamp = 128;			/* ambient super-samples */
  int  ambounce = 0;			/* ambient bounces */
  char  *amblist[AMBLLEN];		/* ambient include/exclude list */
  int  ambincl = -1;			/* include == 1, exclude == 0 */
  
  int  ralrm = 0;				/* seconds between reports */
  
  double	pctdone = 0.0;			/* percentage done */
  time_t  tlastrept = 0L;			/* time at last report */
  time_t  tstart;				/* starting time */
  
  #define	 MAXDIV		16		/* maximum sample size */
  
  #define	 pixjitter()	(.5+dstrpix*(.5-frandom()))
  
  int  hres, vres;			/* resolution for this frame */
  
  static VIEW	lastview;		/* the previous view input */
  
  static void report(int);
  static int nextview(FILE *fp);
  static void render(char *zfile, char *oldfile);
  static void fillscanline(COLOR *scanline, float *zline, char *sd, int xres,
  		int y, int xstep);
  static void fillscanbar(COLOR *scanbar[], float *zbar[], int xres,
  		int y, int ysize);
  static int fillsample(COLOR *colline, float *zline, int x, int y,
  		int xlen, int ylen, int b);
  static double pixvalue(COLOR  col, int  x, int  y);
  static int salvage(char  *oldfile);
  static int pixnumber(int  x, int  y, int  xres, int  yres);
  
  
  
  #ifdef RHAS_STAT
  #include  <sys/types.h>
  #include  <sys/stat.h>
  int
  file_exists(fname)				/* ordinary file exists? */
  char  *fname;
  {
  	struct stat  sbuf;
  	if (stat(fname, &sbuf) < 0) return(0);
  	return((sbuf.st_mode & S_IFREG) != 0);
  }
  #else
  #define  file_exists(f)	(access(f,F_OK)==0)
  #endif
  
  
  void
  quit(code)			/* quit program */
  int  code;
  {
  	if (code)			/* report status */
  		report(0);
  #ifndef NON_POSIX
  	headclean();			/* delete header file */
  	pfclean();			/* clean up persist files */
  #endif
  	exit(code);
  }
  
  
  #ifndef NON_POSIX
  static void
  report(int dummy)		/* report progress */
  {
  	char			bcStat [128];
  	double		u, s;
  #ifdef BSD
  	struct rusage	rubuf;
  #else
  	double		period = 1.0 / 60.0;
  	struct tms	tbuf;
  #endif
  
  	tlastrept = time((time_t *)NULL);
  #ifdef BSD
  	getrusage(RUSAGE_SELF, &rubuf);
  	u = rubuf.ru_utime.tv_sec + rubuf.ru_utime.tv_usec*1e-6;
  	s = rubuf.ru_stime.tv_sec + rubuf.ru_stime.tv_usec*1e-6;
  	getrusage(RUSAGE_CHILDREN, &rubuf);
  	u += rubuf.ru_utime.tv_sec + rubuf.ru_utime.tv_usec*1e-6;
  	s += rubuf.ru_stime.tv_sec + rubuf.ru_stime.tv_usec*1e-6;
  #else
  	times(&tbuf);
  #ifdef _SC_CLK_TCK
  	period = 1.0 / sysconf(_SC_CLK_TCK);
  #endif
  	u = ( tbuf.tms_utime + tbuf.tms_cutime ) * period;
  	s = ( tbuf.tms_stime + tbuf.tms_cstime ) * period;
  #endif
  
  	/* PMAP: Get photon map bias compensation statistics */
  	pmapBiasCompReport(bcStat);
  	
  	sprintf(errmsg,
  			"%lu rays, %s%4.2f%% after %.3fu %.3fs %.3fr hours on %s (PID %d)\n",
  			nrays, bcStat, pctdone, u*(1./3600.), s*(1./3600.),
  			(tlastrept-tstart)*(1./3600.), myhostname(), getpid());
  	eputs(errmsg);
  #ifdef SIGCONT
  	signal(SIGCONT, report);
  #endif
  }
  #else
  static void
  report(int dummy)		/* report progress */
  {
  	char	bcStat [128];
  	
  	tlastrept = time((time_t *)NULL);
  
  	/* PMAP: Get photon map bias compensation statistics */
  	pmapBiasCompReport(bcStat);
  	
  	sprintf(errmsg, "%lu rays, %s%4.2f%% after %5.4f hours\n",
  			nrays, bcStat, pctdone, (tlastrept-tstart)/3600.0);
  	eputs(errmsg);
  }
  #endif
  
  
  void
  rpict(			/* generate image(s) */
  	int  seq,
  	char  *pout,
  	char  *zout,
  	char  *prvr
  )
  /*
   * If seq is greater than zero, then we will render a sequence of
   * images based on view parameter strings read from the standard input.
   * If pout is NULL, then all images will be sent to the standard ouput.
   * If seq is greater than zero and prvr is an integer, then it is the
   * frame number at which rendering should begin.  Preceeding view parameter
   * strings will be skipped in the input.
   * If pout and prvr are the same, prvr is renamed to avoid overwriting.
   * Note that pout and zout should contain %d format specifications for
   * sequenced file naming.
   */
  {
  	char  fbuf[128], fbuf2[128];
  	int  npicts;
  	char  *cp;
  	RESOLU	rs;
  	double	pa;
  					/* check sampling */
  	if (psample < 1)
  		psample = 1;
  	else if (psample > MAXDIV) {
  		sprintf(errmsg, "pixel sampling reduced from %d to %d",
  				psample, MAXDIV);
  		error(WARNING, errmsg);
  		psample = MAXDIV;
  	}
  					/* get starting frame */
  	if (seq <= 0)
  		seq = 0;
  	else if (prvr != NULL && isint(prvr)) {
  		int  rn;		/* skip to specified view */
  		if ((rn = atoi(prvr)) < seq)
  			error(USER, "recover frame less than start frame");
  		if (pout == NULL)
  			error(USER, "missing output file specification");
  		for ( ; seq < rn; seq++)
  			if (nextview(stdin) == EOF)
  				error(USER, "unexpected EOF on view input");
  		setview(&ourview);
  		prvr = fbuf;			/* mark for renaming */
  	}
  	if ((pout != NULL) & (prvr != NULL)) {
  		sprintf(fbuf, pout, seq);
  		if (!strcmp(prvr, fbuf)) {	/* rename */
  			strcpy(fbuf2, fbuf);
  			for (cp = fbuf2; *cp; cp++)
  				;
  			while (cp > fbuf2 && !ISDIRSEP(cp[-1]))
  				cp--;
  			strcpy(cp, RFTEMPLATE);
  			prvr = mktemp(fbuf2);
  			if (rename(fbuf, prvr) < 0) {
  				if (errno == ENOENT) {	/* ghost file */
  					sprintf(errmsg,
  						"new output file \"%s\"",
  						fbuf);
  					error(WARNING, errmsg);
  					prvr = NULL;
  				} else {		/* serious error */
  					sprintf(errmsg,
  					"cannot rename \"%s\" to \"%s\"",
  						fbuf, prvr);
  					error(SYSTEM, errmsg);
  				}
  			}
  		}
  	}
  	npicts = 0;			/* render sequence */
  	do {
  		if (seq && nextview(stdin) == EOF)
  			break;
  		pctdone = 0.0;
  		if (pout != NULL) {
  			sprintf(fbuf, pout, seq);
  			if (file_exists(fbuf)) {
  				if (prvr != NULL || !strcmp(fbuf, pout)) {
  					sprintf(errmsg,
  						"output file \"%s\" exists",
  						fbuf);
  					error(USER, errmsg);
  				}
  				setview(&ourview);
  				continue;		/* don't clobber */
  			}
  			if (freopen(fbuf, "w", stdout) == NULL) {
  				sprintf(errmsg,
  					"cannot open output file \"%s\"", fbuf);
  				error(SYSTEM, errmsg);
  			}
  			SET_FILE_BINARY(stdout);
  			dupheader();
  		}
  		hres = hresolu; vres = vresolu; pa = pixaspect;
  		if (prvr != NULL) {
  			if (viewfile(prvr, &ourview, &rs) <= 0) {
  				sprintf(errmsg,
  			"cannot recover view parameters from \"%s\"", prvr);
  				error(WARNING, errmsg);
  			} else {
  				pa = 0.0;
  				hres = scanlen(&rs);
  				vres = numscans(&rs);
  			}
  		}
  		if ((cp = setview(&ourview)) != NULL)
  			error(USER, cp);
  		normaspect(viewaspect(&ourview), &pa, &hres, &vres);
  		if (seq) {
  			if (ralrm > 0) {
  				fprintf(stderr, "FRAME %d:", seq);
  				fprintview(&ourview, stderr);
  				putc('\n', stderr);
  				fflush(stderr);
  			}
  			printf("FRAME=%d\n", seq);
  		}
  		fputs(VIEWSTR, stdout);
  		fprintview(&ourview, stdout);
  		putchar('\n');
  		if ((pa < .99) | (pa > 1.01))
  			fputaspect(pa, stdout);
  		fputnow(stdout);
  		fputformat(COLRFMT, stdout);
  		putchar('\n');
  		if (zout != NULL)
  			sprintf(cp=fbuf, zout, seq);
  		else
  			cp = NULL;
  		render(cp, prvr);
  		prvr = NULL;
  		npicts++;
  	} while (seq++);
  					/* check that we did something */
  	if (npicts == 0)
  		error(WARNING, "no output produced");
  }
  
  
  static int
  nextview(				/* get next view from fp */
  	FILE  *fp
  )
  {
  	char  linebuf[256];
  
  	lastview = ourview;
  	while (fgets(linebuf, sizeof(linebuf), fp) != NULL)
  		if (isview(linebuf) && sscanview(&ourview, linebuf) > 0)
  			return(0);
  	return(EOF);
  }	
  
  
  static void
  render(				/* render the scene */
  	char  *zfile,
  	char  *oldfile
  )
  {
  	COLOR  *scanbar[MAXDIV+1];	/* scanline arrays of pixel values */
  	float  *zbar[MAXDIV+1];		/* z values */
  	char  *sampdens;		/* previous sample density */
  	int  ypos;			/* current scanline */
  	int  ystep;			/* current y step size */
  	int  hstep;			/* h step size */
  	int  zfd;
  	COLOR  *colptr;
  	float  *zptr;
  	int  i;
  					/* check for empty image */
  	if ((hres <= 0) | (vres <= 0)) {
  		error(WARNING, "empty output picture");
  		fprtresolu(0, 0, stdout);
  		return;
  	}
  					/* allocate scanlines */
  	for (i = 0; i <= psample; i++) {
  		scanbar[i] = (COLOR *)malloc(hres*sizeof(COLOR));
  		if (scanbar[i] == NULL)
  			goto memerr;
  	}
  	hstep = (psample*140+49)/99;		/* quincunx sampling */
  	ystep = (psample*99+70)/140;
  	if (hstep > 2) {
  		i = hres/hstep + 2;
  		if ((sampdens = (char *)malloc(i)) == NULL)
  			goto memerr;
  		while (i--)
  			sampdens[i] = hstep;
  	} else
  		sampdens = NULL;
  					/* open z-file */
  	if (zfile != NULL) {
  		if ((zfd = open(zfile, O_WRONLY|O_CREAT, 0666)) == -1) {
  			sprintf(errmsg, "cannot open z-file \"%s\"", zfile);
  			error(SYSTEM, errmsg);
  		}
  		SET_FD_BINARY(zfd);
  		for (i = 0; i <= psample; i++) {
  			zbar[i] = (float *)malloc(hres*sizeof(float));
  			if (zbar[i] == NULL)
  				goto memerr;
  		}
  	} else {
  		zfd = -1;
  		for (i = 0; i <= psample; i++)
  			zbar[i] = NULL;
  	}
  					/* write out boundaries */
  	fprtresolu(hres, vres, stdout);
  					/* recover file and compute first */
  	i = salvage(oldfile);
  	if (i >= vres)
  		goto alldone;
  	if ((zfd != -1) & (i > 0) &&
  			lseek(zfd, (off_t)i*hres*sizeof(float), SEEK_SET) < 0)
  		error(SYSTEM, "z-file seek error in render");
  	pctdone = 100.0*i/vres;
  	if (ralrm > 0)			/* report init stats */
  		report(0);
  #ifdef SIGCONT
  	else
  	signal(SIGCONT, report);
  #endif
  	ypos = vres-1 - i;			/* initialize sampling */
  	if (directvis)
  		init_drawsources(psample);
  	fillscanline(scanbar[0], zbar[0], sampdens, hres, ypos, hstep);
  						/* compute scanlines */
  	for (ypos -= ystep; ypos > -ystep; ypos -= ystep) {
  							/* bottom adjust? */
  		if (ypos < 0) {
  			ystep += ypos;
  			ypos = 0;
  		}
  		colptr = scanbar[ystep];		/* move base to top */
  		scanbar[ystep] = scanbar[0];
  		scanbar[0] = colptr;
  		zptr = zbar[ystep];
  		zbar[ystep] = zbar[0];
  		zbar[0] = zptr;
  							/* fill base line */
  		fillscanline(scanbar[0], zbar[0], sampdens,
  				hres, ypos, hstep);
  							/* fill bar */
  		fillscanbar(scanbar, zbar, hres, ypos, ystep);
  		if (directvis)				/* add bitty sources */
  			drawsources(scanbar, zbar, 0, hres, ypos, ystep);
  							/* write it out */
  #ifdef SIGCONT
  		signal(SIGCONT, SIG_IGN);	/* don't interrupt writes */
  #endif
  		for (i = ystep; i > 0; i--) {
  			if (zfd != -1 && write(zfd, (char *)zbar[i],
  					hres*sizeof(float))
  					< hres*sizeof(float))
  				goto writerr;
  			if (fwritescan(scanbar[i], hres, stdout) < 0)
  				goto writerr;
  		}
  		if (fflush(stdout) == EOF)
  			goto writerr;
  							/* record progress */
  		pctdone = 100.0*(vres-1-ypos)/vres;
  		if (ralrm > 0 && time((time_t *)NULL) >= tlastrept+ralrm)
  			report(0);
  #ifdef SIGCONT
  		else
  			signal(SIGCONT, report);
  #endif
  	}
  						/* clean up */
  #ifdef SIGCONT
  	signal(SIGCONT, SIG_IGN);
  #endif
  	if (zfd != -1 && write(zfd, (char *)zbar[0], hres*sizeof(float))
  				< hres*sizeof(float))
  		goto writerr;
  	fwritescan(scanbar[0], hres, stdout);
  	if (fflush(stdout) == EOF)
  		goto writerr;
  alldone:
  	if (zfd != -1) {
  		if (close(zfd) == -1)
  			goto writerr;
  		for (i = 0; i <= psample; i++)
  			free((void *)zbar[i]);
  	}
  	for (i = 0; i <= psample; i++)
  		free((void *)scanbar[i]);
  	if (sampdens != NULL)
  		free(sampdens);
  	pctdone = 100.0;
  	if (ralrm > 0)
  		report(0);
  #ifdef SIGCONT
  	signal(SIGCONT, SIG_DFL);
  #endif
  	return;
  writerr:
  	error(SYSTEM, "write error in render");
  memerr:
  	error(SYSTEM, "out of memory in render");
  }
  
  
  static void
  fillscanline(	/* fill scan at y */
  	COLOR	*scanline,
  	float	*zline,
  	char  *sd,
  	int  xres,
  	int  y,
  	int  xstep
  )
  {
  	static int  nc = 0;		/* number of calls */
  	int  bl = xstep, b = xstep;
  	double	z;
  	int  i;
  
  	z = pixvalue(scanline[0], 0, y);
  	if (zline) zline[0] = z;
  				/* zig-zag start for quincunx pattern */
  	for (i = ++nc & 1 ? xstep : xstep/2; i < xres-1+xstep; i += xstep) {
  		if (i >= xres) {
  			xstep += xres-1-i;
  			i = xres-1;
  		}
  		z = pixvalue(scanline[i], i, y);
  		if (zline) zline[i] = z;
  		if (sd) b = sd[0] > sd[1] ? sd[0] : sd[1];
  		if (i <= xstep)
  			b = fillsample(scanline, zline, 0, y, i, 0, b/2);
  		else
  			b = fillsample(scanline+i-xstep,
  					zline ? zline+i-xstep : (float *)NULL,
  					i-xstep, y, xstep, 0, b/2);
  		if (sd) *sd++ = nc & 1 ? bl : b;
  		bl = b;
  	}
  	if (sd && nc & 1) *sd = bl;
  }
  
  
  static void
  fillscanbar(	/* fill interior */
  	COLOR	*scanbar[],
  	float	*zbar[],
  	int  xres,
  	int  y,
  	int  ysize
  )
  {
  	COLOR  vline[MAXDIV+1];
  	float  zline[MAXDIV+1];
  	int  b = ysize;
  	int  i, j;
  
  	for (i = 0; i < xres; i++) {
  		copycolor(vline[0], scanbar[0][i]);
  		copycolor(vline[ysize], scanbar[ysize][i]);
  		if (zbar[0]) {
  			zline[0] = zbar[0][i];
  			zline[ysize] = zbar[ysize][i];
  		}
  		b = fillsample(vline, zbar[0] ? zline : (float *)NULL,
  				i, y, 0, ysize, b/2);
  
  		for (j = 1; j < ysize; j++)
  			copycolor(scanbar[j][i], vline[j]);
  		if (zbar[0])
  			for (j = 1; j < ysize; j++)
  				zbar[j][i] = zline[j];
  	}
  }
  
  
  static int
  fillsample( /* fill interior points */
  	COLOR	*colline,
  	float	*zline,
  	int  x,
  	int  y,
  	int  xlen,
  	int  ylen,
  	int  b
  )
  {
  	double	ratio;
  	double	z;
  	COLOR  ctmp;
  	int  ncut;
  	int  len;
  
  	if (xlen > 0)			/* x or y length is zero */
  		len = xlen;
  	else
  		len = ylen;
  
  	if (len <= 1)			/* limit recursion */
  		return(0);
  
  	if (b > 0 ||
  	(zline && 2.*fabs(zline[0]-zline[len]) > maxdiff*(zline[0]+zline[len]))
  			|| bigdiff(colline[0], colline[len], maxdiff)) {
  
  		z = pixvalue(colline[len>>1], x + (xlen>>1), y + (ylen>>1));
  		if (zline) zline[len>>1] = z;
  		ncut = 1;
  	} else {					/* interpolate */
  		copycolor(colline[len>>1], colline[len]);
  		ratio = (double)(len>>1) / len;
  		scalecolor(colline[len>>1], ratio);
  		if (zline) zline[len>>1] = zline[len] * ratio;
  		ratio = 1.0 - ratio;
  		copycolor(ctmp, colline[0]);
  		scalecolor(ctmp, ratio);
  		addcolor(colline[len>>1], ctmp);
  		if (zline) zline[len>>1] += zline[0] * ratio;
  		ncut = 0;
  	}
  							/* recurse */
  	ncut += fillsample(colline, zline, x, y, xlen>>1, ylen>>1, (b-1)/2);
  
  	ncut += fillsample(colline+(len>>1),
  			zline ? zline+(len>>1) : (float *)NULL,
  			x+(xlen>>1), y+(ylen>>1),
  			xlen-(xlen>>1), ylen-(ylen>>1), b/2);
  
  	return(ncut);
  }
  
  
  static double
  pixvalue(		/* compute pixel value */
  	COLOR  col,			/* returned color */
  	int  x,			/* pixel position */
  	int  y
  )
  {
  	extern void  SDsquare2disk(double ds[2], double seedx, double seedy);
  	RAY  thisray;
  	FVECT	lorg, ldir;
  	double	hpos, vpos, vdist, lmax;
  	int	i;
  						/* compute view ray */
  	setcolor(col, 0.0, 0.0, 0.0);
  	hpos = (x+pixjitter())/hres;
  	vpos = (y+pixjitter())/vres;
  	if ((thisray.rmax = viewray(thisray.rorg, thisray.rdir,
  					&ourview, hpos, vpos)) < -FTINY)
  		return(0.0);
  
  	vdist = ourview.vdist;
  						/* set pixel index */
  	samplendx = pixnumber(x,y,hres,vres);
  						/* optional motion blur */
  	if (lastview.type && mblur > FTINY && (lmax = viewray(lorg, ldir,
  					&lastview, hpos, vpos)) >= -FTINY) {
  		double  d = mblur*(.5-urand(281+samplendx));
  
  		thisray.rmax = (1.-d)*thisray.rmax + d*lmax;
  		for (i = 3; i--; ) {
  			thisray.rorg[i] = (1.-d)*thisray.rorg[i] + d*lorg[i];
  			thisray.rdir[i] = (1.-d)*thisray.rdir[i] + d*ldir[i];
  		}
  		if (normalize(thisray.rdir) == 0.0)
  			return(0.0);
  		vdist = (1.-d)*vdist + d*lastview.vdist;
  	}
  						/* optional depth-of-field */
  	if (dblur > FTINY) {
  		double  vc, df[2];
  						/* random point on disk */
  		SDsquare2disk(df, frandom(), frandom());
  		df[0] *= .5*dblur;
  		df[1] *= .5*dblur;
  		if ((ourview.type == VT_PER) | (ourview.type == VT_PAR)) {
  			double	adj = 1.0;
  			if (ourview.type == VT_PER)
  				adj /= DOT(thisray.rdir, ourview.vdir);
  			df[0] /= sqrt(ourview.hn2);
  			df[1] /= sqrt(ourview.vn2);
  			for (i = 3; i--; ) {
  				vc = ourview.vp[i] + adj*vdist*thisray.rdir[i];
  				thisray.rorg[i] += df[0]*ourview.hvec[i] +
  							df[1]*ourview.vvec[i] ;
  				thisray.rdir[i] = vc - thisray.rorg[i];
  			}
  		} else {			/* non-standard view case */
  			double	dfd = PI/4.*dblur*(.5 - frandom());
  			if ((ourview.type != VT_ANG) & (ourview.type != VT_PLS)) {
  				if (ourview.type != VT_CYL)
  					df[0] /= sqrt(ourview.hn2);
  				df[1] /= sqrt(ourview.vn2);
  			}
  			for (i = 3; i--; ) {
  				vc = ourview.vp[i] + vdist*thisray.rdir[i];
  				thisray.rorg[i] += df[0]*ourview.hvec[i] +
  							df[1]*ourview.vvec[i] +
  							dfd*ourview.vdir[i] ;
  				thisray.rdir[i] = vc - thisray.rorg[i];
  			}
  		}
  		if (normalize(thisray.rdir) == 0.0)
  			return(0.0);
  	}
  
  	rayorigin(&thisray, PRIMARY, NULL, NULL);
  
  	rayvalue(&thisray);			/* trace ray */
  
  	copycolor(col, thisray.rcol);		/* return color */
  
  	return(thisray.rt);			/* return distance */
  }
  
  
  static int
  salvage(		/* salvage scanlines from killed program */
  	char  *oldfile
  )
  {
  	COLR  *scanline;
  	FILE  *fp;
  	int  x, y;
  
  	if (oldfile == NULL)
  		goto gotzip;
  
  	if ((fp = fopen(oldfile, "r")) == NULL) {
  		sprintf(errmsg, "cannot open recover file \"%s\"", oldfile);
  		error(WARNING, errmsg);
  		goto gotzip;
  	}
  	SET_FILE_BINARY(fp);
  				/* discard header */
  	getheader(fp, NULL, NULL);
  				/* get picture size */
  	if (!fscnresolu(&x, &y, fp)) {
  		sprintf(errmsg, "bad recover file \"%s\" - not removed",
  				oldfile);
  		error(WARNING, errmsg);
  		fclose(fp);
  		goto gotzip;
  	}
  
  	if ((x != hres) | (y != vres)) {
  		sprintf(errmsg, "resolution mismatch in recover file \"%s\"",
  				oldfile);
  		error(USER, errmsg);
  	}
  
  	scanline = (COLR *)malloc(hres*sizeof(COLR));
  	if (scanline == NULL)
  		error(SYSTEM, "out of memory in salvage");
  	for (y = 0; y < vres; y++) {
  		if (freadcolrs(scanline, hres, fp) < 0)
  			break;
  		if (fwritecolrs(scanline, hres, stdout) < 0)
  			goto writerr;
  	}
  	if (fflush(stdout) == EOF)
  		goto writerr;
  	free((void *)scanline);
  	fclose(fp);
  	unlink(oldfile);
  	return(y);
  gotzip:
  	if (fflush(stdout) == EOF)
  		error(SYSTEM, "error writing picture header");
  	return(0);
  writerr:
  	sprintf(errmsg, "write error during recovery of \"%s\"", oldfile);
  	error(SYSTEM, errmsg);
  	return -1; /* pro forma return */
  }
  
  static int
  pixnumber(		/* compute pixel index (screen door) */
  	int  x,
  	int  y,
  	int  xres,
  	int  yres
  )
  {
  	unsigned	nbits = 0;
  	bitmask_t	coord[2];
  
  	if (xres < yres) xres = yres;
  	while (xres > 0) {
  		xres >>= 1;
  		++nbits;
  	}
  	coord[0] = x; coord[1] = y;
  	return ((int)hilbert_c2i(2, nbits, coord));
  }
  