| 1 |
/* Copyright (c) 1995 Regents of the University of California */ |
| 2 |
|
| 3 |
#ifndef lint |
| 4 |
static char SCCSid[] = "$SunId$ LBL"; |
| 5 |
#endif |
| 6 |
|
| 7 |
/* |
| 8 |
* Mist volumetric material. |
| 9 |
*/ |
| 10 |
|
| 11 |
#include "ray.h" |
| 12 |
|
| 13 |
#include "source.h" |
| 14 |
|
| 15 |
/* |
| 16 |
* A mist volume is used to specify a region in the scene where a certain |
| 17 |
* light source (or sources) is going to contribute to scattering. The |
| 18 |
* material can add to the existing global medium, and override any ray |
| 19 |
* settings for scattering albedo and eccentricity. Overlapping mist |
| 20 |
* regions should agree w.r.t. albedo and eccentricity, and |
| 21 |
* should have disjoint source lists. |
| 22 |
* |
| 23 |
* A pattern, if used, should compute the line integral of extinction, |
| 24 |
* and will modify the first three arguments directly. This will tend |
| 25 |
* to invalidate results when there are other objects intersected within |
| 26 |
* the mist region. |
| 27 |
* |
| 28 |
* The string arguments for MAT_MIST are the identifiers for the important |
| 29 |
* light sources, which will be looked up in the source array. The last |
| 30 |
* source found matching a name is the one used. A relayed light source |
| 31 |
* may be indicated by the relay surface name, followed by a '>' character, |
| 32 |
* followed by the relayed source name (which may be another relay). |
| 33 |
* |
| 34 |
* Up to five real arguments may be given for MAT_MIST: |
| 35 |
* |
| 36 |
* [ext_r ext_g ext_b [albedo [gecc]]] |
| 37 |
* |
| 38 |
* The primaries indicate medium extinction per unit length (absorption |
| 39 |
* plus scattering). The albedo is the ratio of scattering to extinction, |
| 40 |
* and is set globally by the -ma option (salbedo) and overridden here. |
| 41 |
* The Heyney-Greenstein eccentricity parameter (-mg seccg) indicates how much |
| 42 |
* scattering favors the forward direction. A value of 0 means isotropic |
| 43 |
* scattering. A value approaching 1 indicates strong forward scattering. |
| 44 |
*/ |
| 45 |
|
| 46 |
#define RELAYDELIM '>' /* relay delimiter character */ |
| 47 |
|
| 48 |
extern COLOR cextinction; /* global coefficient of extinction */ |
| 49 |
extern double salbedo; /* global scattering albedo */ |
| 50 |
extern double seccg; /* global scattering eccentricity */ |
| 51 |
|
| 52 |
|
| 53 |
static int |
| 54 |
inslist(sl, n) /* return index of source n if it's in list sl */ |
| 55 |
register int *sl; |
| 56 |
register int n; |
| 57 |
{ |
| 58 |
register int i; |
| 59 |
|
| 60 |
for (i = sl[0]; i > 0; i--) |
| 61 |
if (sl[i] == n) |
| 62 |
return(i); |
| 63 |
return(0); |
| 64 |
} |
| 65 |
|
| 66 |
|
| 67 |
static int |
| 68 |
srcmatch(sp, id) /* check for an id match on a light source */ |
| 69 |
register SRCREC *sp; |
| 70 |
register char *id; |
| 71 |
{ |
| 72 |
extern char *index(); |
| 73 |
register char *cp; |
| 74 |
/* check for relay sources */ |
| 75 |
while ((cp = index(id, RELAYDELIM)) != NULL) { |
| 76 |
if (!(sp->sflags & SVIRTUAL) || sp->so == NULL) |
| 77 |
return(0); |
| 78 |
if (strncmp(id, sp->so->oname, cp-id) || sp->so->oname[cp-id]) |
| 79 |
return(0); |
| 80 |
id = cp + 1; /* relay to next */ |
| 81 |
sp = source + sp->sa.sv.sn; |
| 82 |
} |
| 83 |
if (sp->sflags & SVIRTUAL || sp->so == NULL) |
| 84 |
return(0); |
| 85 |
return(!strcmp(id, sp->so->oname)); |
| 86 |
} |
| 87 |
|
| 88 |
|
| 89 |
static |
| 90 |
add2slist(r, sl) /* add source list to ray's */ |
| 91 |
register RAY *r; |
| 92 |
register int *sl; |
| 93 |
{ |
| 94 |
static int slspare[MAXSLIST+1]; /* in case of emergence */ |
| 95 |
register int i; |
| 96 |
|
| 97 |
if (sl == NULL || sl[0] == 0) /* nothing to add */ |
| 98 |
return; |
| 99 |
if (r->slights == NULL) |
| 100 |
(r->slights = slspare)[0] = 0; /* just once per ray path */ |
| 101 |
for (i = sl[0]; i > 0; i--) |
| 102 |
if (!inslist(r->slights, sl[i])) { |
| 103 |
if (r->slights[0] >= MAXSLIST) |
| 104 |
error(USER, "scattering source list overflow"); |
| 105 |
r->slights[++r->slights[0]] = sl[i]; |
| 106 |
} |
| 107 |
} |
| 108 |
|
| 109 |
|
| 110 |
m_mist(m, r) /* process a ray entering or leaving some mist */ |
| 111 |
OBJREC *m; |
| 112 |
register RAY *r; |
| 113 |
{ |
| 114 |
RAY p; |
| 115 |
int *myslist = NULL; |
| 116 |
int newslist[MAXSLIST+1]; |
| 117 |
COLOR mext; |
| 118 |
double re, ge, be; |
| 119 |
register int i, j; |
| 120 |
/* check arguments */ |
| 121 |
if (m->oargs.nfargs > 5) |
| 122 |
objerror(m, USER, "bad arguments"); |
| 123 |
/* get source indices */ |
| 124 |
if (!(r->crtype & SHADOW) && m->oargs.nsargs > 0 && |
| 125 |
(myslist = (int *)m->os) == NULL) { |
| 126 |
if (m->oargs.nsargs > MAXSLIST) |
| 127 |
objerror(m, USER, "too many sources in list"); |
| 128 |
myslist = (int *)malloc((m->oargs.nsargs+1)*sizeof(int)); |
| 129 |
if (myslist == NULL) |
| 130 |
goto memerr; |
| 131 |
myslist[0] = 0; /* size is first in list */ |
| 132 |
for (j = 0; j < m->oargs.nsargs; j++) { |
| 133 |
i = nsources; /* look up each source id */ |
| 134 |
while (i--) |
| 135 |
if (srcmatch(source+i, m->oargs.sarg[j])) |
| 136 |
break; |
| 137 |
if (i < 0) { |
| 138 |
sprintf(errmsg, "unknown source \"%s\"", |
| 139 |
m->oargs.sarg[j]); |
| 140 |
objerror(m, WARNING, errmsg); |
| 141 |
} else if (inslist(myslist, i)) { |
| 142 |
sprintf(errmsg, "duplicate source \"%s\"", |
| 143 |
m->oargs.sarg[j]); |
| 144 |
objerror(m, WARNING, errmsg); |
| 145 |
} else |
| 146 |
myslist[++myslist[0]] = i; |
| 147 |
} |
| 148 |
m->os = (char *)myslist; |
| 149 |
} |
| 150 |
if (m->oargs.nfargs > 2) { /* compute extinction */ |
| 151 |
setcolor(mext, m->oargs.farg[0], m->oargs.farg[1], |
| 152 |
m->oargs.farg[2]); |
| 153 |
raytexture(r, m->omod); /* get modifiers */ |
| 154 |
multcolor(mext, r->pcol); |
| 155 |
} else |
| 156 |
setcolor(mext, 0., 0., 0.); |
| 157 |
/* start transmitted ray */ |
| 158 |
if (rayorigin(&p, r, TRANS, 1.) < 0) |
| 159 |
return(1); |
| 160 |
VCOPY(p.rdir, r->rdir); |
| 161 |
p.slights = newslist; |
| 162 |
if (r->slights != NULL) /* copy old list if one */ |
| 163 |
for (j = r->slights[0]; j >= 0; j--) |
| 164 |
p.slights[j] = r->slights[j]; |
| 165 |
else |
| 166 |
p.slights[0] = 0; |
| 167 |
if (r->rod > 0.) { /* entering ray */ |
| 168 |
addcolor(p.cext, mext); |
| 169 |
if (m->oargs.nfargs > 3) |
| 170 |
p.albedo = m->oargs.farg[3]; |
| 171 |
if (m->oargs.nfargs > 4) |
| 172 |
p.gecc = m->oargs.farg[4]; |
| 173 |
add2slist(&p, myslist); /* add to list */ |
| 174 |
} else { /* leaving ray */ |
| 175 |
if (myslist != NULL) { /* delete from list */ |
| 176 |
for (j = myslist[0]; j > 0; j--) |
| 177 |
if (i = inslist(p.slights, myslist[j])) |
| 178 |
p.slights[i] = -1; |
| 179 |
for (i = 0, j = 1; j <= p.slights[0]; j++) |
| 180 |
if (p.slights[j] != -1) |
| 181 |
p.slights[++i] = p.slights[j]; |
| 182 |
if (p.slights[0] - i < myslist[0]) { /* fix old */ |
| 183 |
addcolor(r->cext, mext); |
| 184 |
if (m->oargs.nfargs > 3) |
| 185 |
r->albedo = m->oargs.farg[3]; |
| 186 |
if (m->oargs.nfargs > 4) |
| 187 |
r->gecc = m->oargs.farg[4]; |
| 188 |
add2slist(r, myslist); |
| 189 |
} |
| 190 |
p.slights[0] = i; |
| 191 |
} |
| 192 |
re = colval(r->cext,RED) - colval(mext,RED); |
| 193 |
ge = colval(r->cext,GRN) - colval(mext,GRN); |
| 194 |
be = colval(r->cext,BLU) - colval(mext,BLU); |
| 195 |
setcolor(p.cext, re<0. ? 0. : re, |
| 196 |
ge<0. ? 0. : ge, |
| 197 |
be<0. ? 0. : be); |
| 198 |
if (m->oargs.nfargs > 3) |
| 199 |
p.albedo = salbedo; |
| 200 |
if (m->oargs.nfargs > 4) |
| 201 |
p.gecc = seccg; |
| 202 |
} |
| 203 |
rayvalue(&p); /* calls rayparticipate() */ |
| 204 |
copycolor(r->rcol, p.rcol); /* return value */ |
| 205 |
r->rt = r->rot + p.rt; |
| 206 |
return(1); |
| 207 |
memerr: |
| 208 |
error(SYSTEM, "out of memory in m_mist"); |
| 209 |
} |
