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root/radiance/ray/src/rt/rpict.c
Revision: 2.50
Committed: Mon Apr 13 14:01:08 1998 UTC (26 years ago) by gwlarson
Content type: text/plain
Branch: MAIN
Changes since 2.49: +2 -0 lines
Log Message:
added missing calls to setview()

File Contents

# Content
1 /* Copyright (c) 1996 Regents of the University of California */
2
3 #ifndef lint
4 static char SCCSid[] = "$SunId$ LBL";
5 #endif
6
7 /*
8 * rpict.c - routines and variables for picture generation.
9 */
10
11 #include "ray.h"
12
13 #include <sys/types.h>
14
15 #ifndef NIX
16 #ifdef BSD
17 #include <sys/time.h>
18 #include <sys/resource.h>
19 #else
20 #include <sys/times.h>
21 #include <unistd.h>
22 #endif
23 #endif
24
25 extern time_t time();
26
27 #include <signal.h>
28
29 #include "view.h"
30
31 #include "resolu.h"
32
33 #include "random.h"
34
35 #include "paths.h"
36
37 #define RFTEMPLATE "rfXXXXXX"
38
39 #ifndef SIGCONT
40 #define SIGCONT SIGIO
41 #endif
42
43 int dimlist[MAXDIM]; /* sampling dimensions */
44 int ndims = 0; /* number of sampling dimensions */
45 int samplendx; /* sample index number */
46
47 VIEW ourview = STDVIEW; /* view parameters */
48 int hresolu = 512; /* horizontal resolution */
49 int vresolu = 512; /* vertical resolution */
50 double pixaspect = 1.0; /* pixel aspect ratio */
51
52 int psample = 4; /* pixel sample size */
53 double maxdiff = .05; /* max. difference for interpolation */
54 double dstrpix = 0.67; /* square pixel distribution */
55
56 double mblur = 0.; /* motion blur parameter */
57
58 double dstrsrc = 0.0; /* square source distribution */
59 double shadthresh = .05; /* shadow threshold */
60 double shadcert = .5; /* shadow certainty */
61 int directrelay = 1; /* number of source relays */
62 int vspretest = 512; /* virtual source pretest density */
63 int directvis = 1; /* sources visible? */
64 double srcsizerat = .25; /* maximum ratio source size/dist. */
65
66 COLOR cextinction = BLKCOLOR; /* global extinction coefficient */
67 COLOR salbedo = BLKCOLOR; /* global scattering albedo */
68 double seccg = 0.; /* global scattering eccentricity */
69 double ssampdist = 0.; /* scatter sampling distance */
70
71 double specthresh = .15; /* specular sampling threshold */
72 double specjitter = 1.; /* specular sampling jitter */
73
74 int backvis = 1; /* back face visibility */
75
76 int maxdepth = 6; /* maximum recursion depth */
77 double minweight = 5e-3; /* minimum ray weight */
78
79 COLOR ambval = BLKCOLOR; /* ambient value */
80 int ambvwt = 0; /* initial weight for ambient value */
81 double ambacc = 0.2; /* ambient accuracy */
82 int ambres = 32; /* ambient resolution */
83 int ambdiv = 128; /* ambient divisions */
84 int ambssamp = 0; /* ambient super-samples */
85 int ambounce = 0; /* ambient bounces */
86 char *amblist[128]; /* ambient include/exclude list */
87 int ambincl = -1; /* include == 1, exclude == 0 */
88
89 #ifdef MSDOS
90 int ralrm = 60; /* seconds between reports */
91 #else
92 int ralrm = 0; /* seconds between reports */
93 #endif
94
95 double pctdone = 0.0; /* percentage done */
96
97 time_t tlastrept = 0L; /* time at last report */
98
99 extern time_t tstart; /* starting time */
100
101 extern unsigned long nrays; /* number of rays traced */
102
103 #define MAXDIV 16 /* maximum sample size */
104
105 #define pixjitter() (.5+dstrpix*(.5-frandom()))
106
107 int hres, vres; /* resolution for this frame */
108
109 static VIEW lastview; /* the previous view input */
110
111 extern char *mktemp();
112
113 double pixvalue();
114
115 #ifdef NIX
116 #define file_exists(f) (access(f,F_OK)==0)
117 #else
118 #include <sys/types.h>
119 #include <sys/stat.h>
120 int
121 file_exists(fname) /* ordinary file exists? */
122 char *fname;
123 {
124 struct stat sbuf;
125 if (stat(fname, &sbuf) < 0) return(0);
126 return((sbuf.st_mode & S_IFREG) != 0);
127 }
128 #endif
129
130
131 quit(code) /* quit program */
132 int code;
133 {
134 if (code) /* report status */
135 report();
136 headclean(); /* delete header file */
137 pfclean(); /* clean up persist files */
138 exit(code);
139 }
140
141
142 #ifndef NIX
143 report() /* report progress */
144 {
145 extern char *myhostname();
146 double u, s;
147 #ifdef BSD
148 struct rusage rubuf;
149 #else
150 struct tms tbuf;
151 double period;
152 #endif
153
154 tlastrept = time((time_t *)NULL);
155 #ifdef BSD
156 getrusage(RUSAGE_SELF, &rubuf);
157 u = rubuf.ru_utime.tv_sec + rubuf.ru_utime.tv_usec/1e6;
158 s = rubuf.ru_stime.tv_sec + rubuf.ru_stime.tv_usec/1e6;
159 getrusage(RUSAGE_CHILDREN, &rubuf);
160 u += rubuf.ru_utime.tv_sec + rubuf.ru_utime.tv_usec/1e6;
161 s += rubuf.ru_stime.tv_sec + rubuf.ru_stime.tv_usec/1e6;
162 #else
163 times(&tbuf);
164 #ifdef _SC_CLK_TCK
165 period = 1.0 / sysconf(_SC_CLK_TCK);
166 #else
167 period = 1.0 / 60.0;
168 #endif
169 u = ( tbuf.tms_utime + tbuf.tms_cutime ) * period;
170 s = ( tbuf.tms_stime + tbuf.tms_cstime ) * period;
171 #endif
172
173 sprintf(errmsg,
174 "%lu rays, %4.2f%% after %.3fu %.3fs %.3fr hours on %s\n",
175 nrays, pctdone, u/3600., s/3600.,
176 (tlastrept-tstart)/3600., myhostname());
177 eputs(errmsg);
178 #ifndef BSD
179 signal(SIGCONT, report);
180 #endif
181 }
182 #else
183 report() /* report progress */
184 {
185 tlastrept = time((time_t *)NULL);
186 sprintf(errmsg, "%lu rays, %4.2f%% after %5.4f hours\n",
187 nrays, pctdone, (tlastrept-tstart)/3600.0);
188 eputs(errmsg);
189 }
190 #endif
191
192
193 rpict(seq, pout, zout, prvr) /* generate image(s) */
194 int seq;
195 char *pout, *zout, *prvr;
196 /*
197 * If seq is greater than zero, then we will render a sequence of
198 * images based on view parameter strings read from the standard input.
199 * If pout is NULL, then all images will be sent to the standard ouput.
200 * If seq is greater than zero and prvr is an integer, then it is the
201 * frame number at which rendering should begin. Preceeding view parameter
202 * strings will be skipped in the input.
203 * If pout and prvr are the same, prvr is renamed to avoid overwriting.
204 * Note that pout and zout should contain %d format specifications for
205 * sequenced file naming.
206 */
207 {
208 extern char *rindex(), *strncpy(), *strcat(), *strcpy();
209 char fbuf[128], fbuf2[128];
210 int npicts;
211 register char *cp;
212 RESOLU rs;
213 double pa;
214 /* check sampling */
215 if (psample < 1)
216 psample = 1;
217 else if (psample > MAXDIV) {
218 sprintf(errmsg, "pixel sampling reduced from %d to %d",
219 psample, MAXDIV);
220 error(WARNING, errmsg);
221 psample = MAXDIV;
222 }
223 /* get starting frame */
224 if (seq <= 0)
225 seq = 0;
226 else if (prvr != NULL && isint(prvr)) {
227 register int rn; /* skip to specified view */
228 if ((rn = atoi(prvr)) < seq)
229 error(USER, "recover frame less than start frame");
230 if (pout == NULL)
231 error(USER, "missing output file specification");
232 for ( ; seq < rn; seq++)
233 if (nextview(stdin) == EOF)
234 error(USER, "unexpected EOF on view input");
235 setview(&ourview);
236 prvr = fbuf; /* mark for renaming */
237 }
238 if (pout != NULL & prvr != NULL) {
239 sprintf(fbuf, pout, seq);
240 if (!strcmp(prvr, fbuf)) { /* rename */
241 strcpy(fbuf2, fbuf);
242 for (cp = fbuf2; *cp; cp++)
243 ;
244 while (cp > fbuf2 && !ISDIRSEP(cp[-1]))
245 cp--;
246 strcpy(cp, RFTEMPLATE);
247 prvr = mktemp(fbuf2);
248 if (rename(fbuf, prvr) < 0)
249 if (errno == ENOENT) { /* ghost file */
250 sprintf(errmsg,
251 "new output file \"%s\"",
252 fbuf);
253 error(WARNING, errmsg);
254 prvr = NULL;
255 } else { /* serious error */
256 sprintf(errmsg,
257 "cannot rename \"%s\" to \"%s\"",
258 fbuf, prvr);
259 error(SYSTEM, errmsg);
260 }
261 }
262 }
263 npicts = 0; /* render sequence */
264 do {
265 if (seq && nextview(stdin) == EOF)
266 break;
267 pctdone = 0.0;
268 if (pout != NULL) {
269 sprintf(fbuf, pout, seq);
270 if (file_exists(fbuf)) {
271 if (prvr != NULL || !strcmp(fbuf, pout)) {
272 sprintf(errmsg,
273 "output file \"%s\" exists",
274 fbuf);
275 error(USER, errmsg);
276 }
277 setview(&ourview);
278 continue; /* don't clobber */
279 }
280 if (freopen(fbuf, "w", stdout) == NULL) {
281 sprintf(errmsg,
282 "cannot open output file \"%s\"", fbuf);
283 error(SYSTEM, errmsg);
284 }
285 #ifdef MSDOS
286 setmode(fileno(stdout), O_BINARY);
287 #endif
288 dupheader();
289 }
290 hres = hresolu; vres = vresolu; pa = pixaspect;
291 if (prvr != NULL)
292 if (viewfile(prvr, &ourview, &rs) <= 0
293 || rs.or != PIXSTANDARD) {
294 sprintf(errmsg,
295 "cannot recover view parameters from \"%s\"", prvr);
296 error(WARNING, errmsg);
297 } else {
298 pa = 0.0;
299 hres = scanlen(&rs);
300 vres = numscans(&rs);
301 }
302 if ((cp = setview(&ourview)) != NULL)
303 error(USER, cp);
304 normaspect(viewaspect(&ourview), &pa, &hres, &vres);
305 if (seq) {
306 if (ralrm > 0) {
307 fprintf(stderr, "FRAME %d:", seq);
308 fprintview(&ourview, stderr);
309 putc('\n', stderr);
310 fflush(stderr);
311 }
312 printf("FRAME=%d\n", seq);
313 }
314 fputs(VIEWSTR, stdout);
315 fprintview(&ourview, stdout);
316 putchar('\n');
317 if (pa < .99 || pa > 1.01)
318 fputaspect(pa, stdout);
319 fputformat(COLRFMT, stdout);
320 putchar('\n');
321 if (zout != NULL)
322 sprintf(cp=fbuf, zout, seq);
323 else
324 cp = NULL;
325 render(cp, prvr);
326 prvr = NULL;
327 npicts++;
328 } while (seq++);
329 /* check that we did something */
330 if (npicts == 0)
331 error(WARNING, "no output produced");
332 }
333
334
335 nextview(fp) /* get next view from fp */
336 FILE *fp;
337 {
338 char linebuf[256];
339
340 copystruct(&lastview, &ourview);
341 while (fgets(linebuf, sizeof(linebuf), fp) != NULL)
342 if (isview(linebuf) && sscanview(&ourview, linebuf) > 0)
343 return(0);
344 return(EOF);
345 }
346
347
348 render(zfile, oldfile) /* render the scene */
349 char *zfile, *oldfile;
350 {
351 extern long lseek();
352 COLOR *scanbar[MAXDIV+1]; /* scanline arrays of pixel values */
353 float *zbar[MAXDIV+1]; /* z values */
354 char *sampdens; /* previous sample density */
355 int ypos; /* current scanline */
356 int ystep; /* current y step size */
357 int hstep; /* h step size */
358 int zfd;
359 COLOR *colptr;
360 float *zptr;
361 register int i;
362 /* allocate scanlines */
363 for (i = 0; i <= psample; i++) {
364 scanbar[i] = (COLOR *)malloc(hres*sizeof(COLOR));
365 if (scanbar[i] == NULL)
366 goto memerr;
367 }
368 hstep = (psample*140+49)/99; /* quincunx sampling */
369 ystep = (psample*99+70)/140;
370 if (hstep > 2) {
371 i = hres/hstep + 2;
372 if ((sampdens = malloc(i)) == NULL)
373 goto memerr;
374 while (i--)
375 sampdens[i] = hstep;
376 } else
377 sampdens = NULL;
378 /* open z-file */
379 if (zfile != NULL) {
380 if ((zfd = open(zfile, O_WRONLY|O_CREAT, 0666)) == -1) {
381 sprintf(errmsg, "cannot open z-file \"%s\"", zfile);
382 error(SYSTEM, errmsg);
383 }
384 #ifdef MSDOS
385 setmode(zfd, O_BINARY);
386 #endif
387 for (i = 0; i <= psample; i++) {
388 zbar[i] = (float *)malloc(hres*sizeof(float));
389 if (zbar[i] == NULL)
390 goto memerr;
391 }
392 } else {
393 zfd = -1;
394 for (i = 0; i <= psample; i++)
395 zbar[i] = NULL;
396 }
397 /* write out boundaries */
398 fprtresolu(hres, vres, stdout);
399 /* recover file and compute first */
400 i = salvage(oldfile);
401 if (i >= vres)
402 goto alldone;
403 if (zfd != -1 && i > 0 &&
404 lseek(zfd, (long)i*hres*sizeof(float), 0) == -1)
405 error(SYSTEM, "z-file seek error in render");
406 pctdone = 100.0*i/vres;
407 if (ralrm > 0) /* report init stats */
408 report();
409 #ifndef BSD
410 else
411 #endif
412 signal(SIGCONT, report);
413 ypos = vres-1 - i; /* initialize sampling */
414 if (directvis)
415 init_drawsources(psample);
416 fillscanline(scanbar[0], zbar[0], sampdens, hres, ypos, hstep);
417 /* compute scanlines */
418 for (ypos -= ystep; ypos > -ystep; ypos -= ystep) {
419 /* bottom adjust? */
420 if (ypos < 0) {
421 ystep += ypos;
422 ypos = 0;
423 }
424 colptr = scanbar[ystep]; /* move base to top */
425 scanbar[ystep] = scanbar[0];
426 scanbar[0] = colptr;
427 zptr = zbar[ystep];
428 zbar[ystep] = zbar[0];
429 zbar[0] = zptr;
430 /* fill base line */
431 fillscanline(scanbar[0], zbar[0], sampdens,
432 hres, ypos, hstep);
433 /* fill bar */
434 fillscanbar(scanbar, zbar, hres, ypos, ystep);
435 if (directvis) /* add bitty sources */
436 drawsources(scanbar, zbar, 0, hres, ypos, ystep);
437 /* write it out */
438 #ifndef BSD
439 signal(SIGCONT, SIG_IGN); /* don't interrupt writes */
440 #endif
441 for (i = ystep; i > 0; i--) {
442 if (zfd != -1 && write(zfd, (char *)zbar[i],
443 hres*sizeof(float))
444 < hres*sizeof(float))
445 goto writerr;
446 if (fwritescan(scanbar[i], hres, stdout) < 0)
447 goto writerr;
448 }
449 if (fflush(stdout) == EOF)
450 goto writerr;
451 /* record progress */
452 pctdone = 100.0*(vres-1-ypos)/vres;
453 if (ralrm > 0 && time((time_t *)NULL) >= tlastrept+ralrm)
454 report();
455 #ifndef BSD
456 else
457 signal(SIGCONT, report);
458 #endif
459 }
460 /* clean up */
461 signal(SIGCONT, SIG_IGN);
462 if (zfd != -1 && write(zfd, (char *)zbar[0], hres*sizeof(float))
463 < hres*sizeof(float))
464 goto writerr;
465 fwritescan(scanbar[0], hres, stdout);
466 if (fflush(stdout) == EOF)
467 goto writerr;
468 alldone:
469 if (zfd != -1) {
470 if (close(zfd) == -1)
471 goto writerr;
472 for (i = 0; i <= psample; i++)
473 free((char *)zbar[i]);
474 }
475 for (i = 0; i <= psample; i++)
476 free((char *)scanbar[i]);
477 if (sampdens != NULL)
478 free(sampdens);
479 pctdone = 100.0;
480 if (ralrm > 0)
481 report();
482 signal(SIGCONT, SIG_DFL);
483 return;
484 writerr:
485 error(SYSTEM, "write error in render");
486 memerr:
487 error(SYSTEM, "out of memory in render");
488 }
489
490
491 fillscanline(scanline, zline, sd, xres, y, xstep) /* fill scan at y */
492 register COLOR *scanline;
493 register float *zline;
494 register char *sd;
495 int xres, y, xstep;
496 {
497 static int nc = 0; /* number of calls */
498 int bl = xstep, b = xstep;
499 double z;
500 register int i;
501
502 z = pixvalue(scanline[0], 0, y);
503 if (zline) zline[0] = z;
504 /* zig-zag start for quincunx pattern */
505 for (i = ++nc & 1 ? xstep : xstep/2; i < xres-1+xstep; i += xstep) {
506 if (i >= xres) {
507 xstep += xres-1-i;
508 i = xres-1;
509 }
510 z = pixvalue(scanline[i], i, y);
511 if (zline) zline[i] = z;
512 if (sd) b = sd[0] > sd[1] ? sd[0] : sd[1];
513 if (i <= xstep)
514 b = fillsample(scanline, zline, 0, y, i, 0, b/2);
515 else
516 b = fillsample(scanline+i-xstep,
517 zline ? zline+i-xstep : (float *)NULL,
518 i-xstep, y, xstep, 0, b/2);
519 if (sd) *sd++ = nc & 1 ? bl : b;
520 bl = b;
521 }
522 if (sd && nc & 1) *sd = bl;
523 }
524
525
526 fillscanbar(scanbar, zbar, xres, y, ysize) /* fill interior */
527 register COLOR *scanbar[];
528 register float *zbar[];
529 int xres, y, ysize;
530 {
531 COLOR vline[MAXDIV+1];
532 float zline[MAXDIV+1];
533 int b = ysize;
534 register int i, j;
535
536 for (i = 0; i < xres; i++) {
537 copycolor(vline[0], scanbar[0][i]);
538 copycolor(vline[ysize], scanbar[ysize][i]);
539 if (zbar[0]) {
540 zline[0] = zbar[0][i];
541 zline[ysize] = zbar[ysize][i];
542 }
543 b = fillsample(vline, zbar[0] ? zline : (float *)NULL,
544 i, y, 0, ysize, b/2);
545
546 for (j = 1; j < ysize; j++)
547 copycolor(scanbar[j][i], vline[j]);
548 if (zbar[0])
549 for (j = 1; j < ysize; j++)
550 zbar[j][i] = zline[j];
551 }
552 }
553
554
555 int
556 fillsample(colline, zline, x, y, xlen, ylen, b) /* fill interior points */
557 register COLOR *colline;
558 register float *zline;
559 int x, y;
560 int xlen, ylen;
561 int b;
562 {
563 double ratio;
564 double z;
565 COLOR ctmp;
566 int ncut;
567 register int len;
568
569 if (xlen > 0) /* x or y length is zero */
570 len = xlen;
571 else
572 len = ylen;
573
574 if (len <= 1) /* limit recursion */
575 return(0);
576
577 if (b > 0 ||
578 (zline && 2.*fabs(zline[0]-zline[len]) > maxdiff*(zline[0]+zline[len]))
579 || bigdiff(colline[0], colline[len], maxdiff)) {
580
581 z = pixvalue(colline[len>>1], x + (xlen>>1), y + (ylen>>1));
582 if (zline) zline[len>>1] = z;
583 ncut = 1;
584 } else { /* interpolate */
585 copycolor(colline[len>>1], colline[len]);
586 ratio = (double)(len>>1) / len;
587 scalecolor(colline[len>>1], ratio);
588 if (zline) zline[len>>1] = zline[len] * ratio;
589 ratio = 1.0 - ratio;
590 copycolor(ctmp, colline[0]);
591 scalecolor(ctmp, ratio);
592 addcolor(colline[len>>1], ctmp);
593 if (zline) zline[len>>1] += zline[0] * ratio;
594 ncut = 0;
595 }
596 /* recurse */
597 ncut += fillsample(colline, zline, x, y, xlen>>1, ylen>>1, (b-1)/2);
598
599 ncut += fillsample(colline+(len>>1),
600 zline ? zline+(len>>1) : (float *)NULL,
601 x+(xlen>>1), y+(ylen>>1),
602 xlen-(xlen>>1), ylen-(ylen>>1), b/2);
603
604 return(ncut);
605 }
606
607
608 double
609 pixvalue(col, x, y) /* compute pixel value */
610 COLOR col; /* returned color */
611 int x, y; /* pixel position */
612 {
613 RAY thisray;
614 FVECT lorg, ldir;
615 double hpos, vpos, lmax, d;
616 /* compute view ray */
617 hpos = (x+pixjitter())/hres;
618 vpos = (y+pixjitter())/vres;
619 if ((thisray.rmax = viewray(thisray.rorg, thisray.rdir,
620 &ourview, hpos, vpos)) < -FTINY) {
621 setcolor(col, 0.0, 0.0, 0.0);
622 return(0.0);
623 }
624
625 samplendx = pixnumber(x,y,hres,vres); /* set pixel index */
626
627 /* optional motion blur */
628 if (lastview.type && mblur > FTINY && (lmax = viewray(lorg, ldir,
629 &lastview, hpos, vpos)) >= -FTINY) {
630 register int i;
631 register double d = mblur*(.5-urand(281+samplendx));
632
633 thisray.rmax = (1.-d)*thisray.rmax + d*lmax;
634 for (i = 3; i--; ) {
635 thisray.rorg[i] = (1.-d)*thisray.rorg[i] + d*lorg[i];
636 thisray.rdir[i] = (1.-d)*thisray.rdir[i] + d*ldir[i];
637 }
638 if (normalize(thisray.rdir) == 0.0)
639 return(0.0);
640 }
641
642 rayorigin(&thisray, NULL, PRIMARY, 1.0);
643
644 rayvalue(&thisray); /* trace ray */
645
646 copycolor(col, thisray.rcol); /* return color */
647
648 return(thisray.rt); /* return distance */
649 }
650
651
652 int
653 salvage(oldfile) /* salvage scanlines from killed program */
654 char *oldfile;
655 {
656 COLR *scanline;
657 FILE *fp;
658 int x, y;
659
660 if (oldfile == NULL)
661 goto gotzip;
662
663 if ((fp = fopen(oldfile, "r")) == NULL) {
664 sprintf(errmsg, "cannot open recover file \"%s\"", oldfile);
665 error(WARNING, errmsg);
666 goto gotzip;
667 }
668 #ifdef MSDOS
669 setmode(fileno(fp), O_BINARY);
670 #endif
671 /* discard header */
672 getheader(fp, NULL, NULL);
673 /* get picture size */
674 if (!fscnresolu(&x, &y, fp)) {
675 sprintf(errmsg, "bad recover file \"%s\" - not removed",
676 oldfile);
677 error(WARNING, errmsg);
678 fclose(fp);
679 goto gotzip;
680 }
681
682 if (x != hres || y != vres) {
683 sprintf(errmsg, "resolution mismatch in recover file \"%s\"",
684 oldfile);
685 error(USER, errmsg);
686 }
687
688 scanline = (COLR *)malloc(hres*sizeof(COLR));
689 if (scanline == NULL)
690 error(SYSTEM, "out of memory in salvage");
691 for (y = 0; y < vres; y++) {
692 if (freadcolrs(scanline, hres, fp) < 0)
693 break;
694 if (fwritecolrs(scanline, hres, stdout) < 0)
695 goto writerr;
696 }
697 if (fflush(stdout) == EOF)
698 goto writerr;
699 free((char *)scanline);
700 fclose(fp);
701 unlink(oldfile);
702 return(y);
703 gotzip:
704 if (fflush(stdout) == EOF)
705 error(SYSTEM, "error writing picture header");
706 return(0);
707 writerr:
708 sprintf(errmsg, "write error during recovery of \"%s\"", oldfile);
709 error(SYSTEM, errmsg);
710 }
711
712
713 int
714 pixnumber(x, y, xres, yres) /* compute pixel index (brushed) */
715 register int x, y;
716 int xres, yres;
717 {
718 x -= y;
719 while (x < 0)
720 x += xres;
721 return((((x>>2)*yres + y) << 2) + (x & 3));
722 }