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/* Copyright (c) 1995 Regents of the University of California */ |
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|
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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#endif |
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|
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/* |
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* Mist volumetric material. |
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*/ |
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|
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#include "ray.h" |
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|
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#include "source.h" |
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|
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/* |
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* A mist volume is used to specify a region in the scene where a certain |
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* light source (or sources) is going to contribute to scattering. The |
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* material can add to the existing global medium, and override any ray |
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* settings for scattering albedo and eccentricity. Overlapping mist |
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* regions should agree w.r.t. albedo and eccentricity, and |
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* should have disjoint source lists. |
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* |
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* A pattern, if used, should compute the line integral of extinction, |
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* and will modify the first three arguments directly. This will tend |
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* to invalidate results when there are other objects intersected within |
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* the mist region. |
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* |
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* The string arguments for MAT_MIST are the identifiers for the important |
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* light sources, which will be looked up in the source array. The last |
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* source found matching a name is the one used. A relayed light source |
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* may be indicated by the relay surface name, followed by a '>' character, |
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* followed by the relayed source name (which may be another relay). |
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* |
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* Up to five real arguments may be given for MAT_MIST: |
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* |
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* [ext_r ext_g ext_b [albedo [gecc]]] |
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* |
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* The primaries indicate medium extinction per unit length (absorption |
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* plus scattering). The albedo is the ratio of scattering to extinction, |
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* and is set globally by the -ma option (salbedo) and overridden here. |
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* The Heyney-Greenstein eccentricity parameter (-mg seccg) indicates how much |
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* scattering favors the forward direction. A value of 0 means isotropic |
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* scattering. A value approaching 1 indicates strong forward scattering. |
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*/ |
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|
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#define MAXSLIST 32 /* maximum sources to check */ |
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#define RELAYDELIM '>' /* relay delimiter character */ |
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|
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extern COLOR cextinction; /* global coefficient of extinction */ |
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extern double salbedo; /* global scattering albedo */ |
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extern double seccg; /* global scattering eccentricity */ |
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|
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|
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static int |
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inslist(sl, n) /* return index of source n if it's in list sl */ |
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register int *sl; |
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register int n; |
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{ |
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register int i; |
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|
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for (i = sl[0]; i > 0; i--) |
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if (sl[i] == n) |
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return(i); |
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return(0); |
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} |
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|
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|
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static int |
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srcmatch(sn, id) /* check for an id match on a light source */ |
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register int sn; |
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char *id; |
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{ |
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extern char *index(); |
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register char *cp; |
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again: |
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if (source[sn].so == NULL) /* just in case */ |
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return(0); |
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if ((cp = index(id, RELAYDELIM)) != NULL) { /* relay source */ |
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if (!(source[sn].sflags & SVIRTUAL)) |
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return(0); |
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*cp = '\0'; |
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if (strcmp(id, source[sn].so->oname)) { |
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*cp = RELAYDELIM; |
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return(0); |
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} |
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*cp = RELAYDELIM; |
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id = cp + 1; /* recurse */ |
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sn = source[sn].sa.sv.sn; |
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goto again; |
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} |
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if (source[sn].sflags & SVIRTUAL) |
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return(0); |
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return(!strcmp(id, source[sn].so->oname)); |
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} |
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|
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|
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m_mist(m, r) /* process a ray entering or leaving some mist */ |
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OBJREC *m; |
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register RAY *r; |
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{ |
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RAY p; |
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int *myslist = NULL; |
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int newslist[MAXSLIST+1]; |
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COLOR mext; |
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double re, ge, be; |
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register int i, j; |
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/* check arguments */ |
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if (m->oargs.nfargs > 5) |
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objerror(m, USER, "bad arguments"); |
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if (m->oargs.nsargs > MAXSLIST) |
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objerror(m, USER, "too many sources in list"); |
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/* get source indices */ |
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if (m->oargs.nsargs > 0 && (myslist = (int *)m->os) == NULL) { |
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myslist = (int *)malloc((m->oargs.nsargs+1)*sizeof(int)); |
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if (myslist == NULL) |
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goto memerr; |
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myslist[0] = m->oargs.nsargs; /* size is first in set */ |
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for (j = myslist[0]; j > 0; j--) { |
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i = nsources; /* look up each source id */ |
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while (i--) |
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if (srcmatch(i, m->oargs.sarg[j-1])) |
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break; |
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if (i < 0) { |
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sprintf(errmsg, "unknown source \"%s\"", |
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m->oargs.sarg[j-1]); |
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objerror(m, WARNING, errmsg); |
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} else |
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myslist[j] = i; |
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} |
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m->os = (char *)myslist; |
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} |
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if (m->oargs.nfargs > 2) { /* compute extinction */ |
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setcolor(mext, m->oargs.farg[0], m->oargs.farg[1], |
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m->oargs.farg[2]); |
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raytexture(r, m->omod); /* get modifiers */ |
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multcolor(mext, r->pcol); |
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} else |
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setcolor(mext, 0., 0., 0.); |
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/* start transmitted ray */ |
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if (rayorigin(&p, r, TRANS, 1.) < 0) |
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return(1); |
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VCOPY(p.rdir, r->rdir); |
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p.slights = newslist; |
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if (r->slights != NULL) |
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for (j = r->slights[0]; j >= 0; j--) |
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p.slights[j] = r->slights[j]; |
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else |
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p.slights[0] = 0; |
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if (r->rod > 0.) { /* entering ray */ |
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addcolor(p.cext, mext); |
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if (m->oargs.nfargs > 3) |
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p.albedo = m->oargs.farg[3]; |
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if (m->oargs.nfargs > 4) |
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p.gecc = m->oargs.farg[4]; |
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if (myslist != NULL) /* add to list */ |
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for (j = myslist[0]; j > 0; j--) |
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if (!inslist(p.slights, myslist[j])) { |
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if (p.slights[0] >= MAXSLIST) |
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error(USER, |
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"scattering source list overflow"); |
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p.slights[++p.slights[0]] = myslist[j]; |
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} |
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} else { /* leaving ray */ |
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re = colval(r->cext,RED) - colval(mext,RED); |
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ge = colval(r->cext,GRN) - colval(mext,GRN); |
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be = colval(r->cext,BLU) - colval(mext,BLU); |
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setcolor(p.cext, re<0. ? 0. : re, |
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ge<0. ? 0. : ge, |
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be<0. ? 0. : be); |
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if (m->oargs.nfargs > 3) |
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p.albedo = salbedo; |
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if (m->oargs.nfargs > 4) |
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p.gecc = seccg; |
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if (myslist != NULL) { /* delete from list */ |
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for (j = myslist[0]; j > 0; j--) |
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if (i = inslist(p.slights, myslist[j])) |
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p.slights[i] = -1; |
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for (i = 0, j = 1; j <= p.slights[0]; j++) |
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if (p.slights[j] != -1) |
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p.slights[++i] = p.slights[j]; |
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p.slights[0] = i; |
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} |
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} |
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rayvalue(&p); /* calls rayparticipate() */ |
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copycolor(r->rcol, p.rcol); /* return value */ |
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r->rt = r->rot + p.rt; |
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return(1); |
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memerr: |
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error(SYSTEM, "out of memory in m_mist"); |
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} |
