1 |
greg |
1.1 |
#ifndef lint |
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greg |
2.23 |
static const char RCSid[] = "$Id: dielectric.c,v 2.22 2010/10/25 22:57:45 greg Exp $"; |
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greg |
1.1 |
#endif |
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/* |
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* dielectric.c - shading function for transparent materials. |
6 |
greg |
2.15 |
*/ |
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greg |
2.16 |
#include "copyright.h" |
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greg |
1.1 |
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#include "ray.h" |
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#include "otypes.h" |
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schorsch |
2.18 |
#include "rtotypes.h" |
13 |
greg |
1.1 |
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#ifdef DISPERSE |
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#include "source.h" |
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schorsch |
2.18 |
static int disperse(OBJREC *m,RAY *r,FVECT vt,double tr,COLOR cet,COLOR abt); |
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static int lambda(OBJREC *m, FVECT v2, FVECT dv, FVECT lr); |
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greg |
1.1 |
#endif |
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schorsch |
2.18 |
static double mylog(double x); |
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greg |
1.1 |
/* |
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* Explicit calculations for Fresnel's equation are performed, |
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* but only one square root computation is necessary. |
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* The index of refraction is given as a Hartmann equation |
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* with lambda0 equal to zero. If the slope of Hartmann's |
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* equation is non-zero, the material disperses light upon |
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* refraction. This condition is examined on rays traced to |
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* light sources. If a ray is exiting a dielectric material, we |
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* check the sources to see if any would cause bright color to be |
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* directed to the viewer due to dispersion. This gives colorful |
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* sparkle to crystals, etc. (Only if DISPERSE is defined!) |
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* |
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* Arguments for MAT_DIELECTRIC are: |
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* red grn blu rndx Hartmann |
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* |
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* Arguments for MAT_INTERFACE are: |
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* red1 grn1 blu1 rndx1 red2 grn2 blu2 rndx2 |
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* |
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* The primaries are material transmission per unit length. |
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* MAT_INTERFACE uses dielectric1 for inside and dielectric2 for |
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* outside. |
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*/ |
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#define MLAMBDA 500 /* mean lambda */ |
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#define MAXLAMBDA 779 /* maximum lambda */ |
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#define MINLAMBDA 380 /* minimum lambda */ |
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#define MINCOS 0.997 /* minimum dot product for dispersion */ |
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greg |
2.9 |
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greg |
2.10 |
static double |
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schorsch |
2.18 |
mylog( /* special log for extinction coefficients */ |
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double x |
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) |
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greg |
2.10 |
{ |
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if (x < 1e-40) |
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return(-100.); |
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if (x >= 1.) |
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return(0.); |
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return(log(x)); |
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} |
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schorsch |
2.18 |
extern int |
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m_dielectric( /* color a ray which hit a dielectric interface */ |
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OBJREC *m, |
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register RAY *r |
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) |
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greg |
1.1 |
{ |
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double cos1, cos2, nratio; |
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greg |
2.9 |
COLOR ctrans; |
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greg |
2.11 |
COLOR talb; |
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gwlarson |
2.14 |
int hastexture; |
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greg |
2.23 |
double transdist=0, transtest=0; |
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double mirdist=0, mirtest=0; |
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greg |
2.19 |
int flatsurface; |
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greg |
1.5 |
double refl, trans; |
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greg |
1.1 |
FVECT dnorm; |
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double d1, d2; |
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RAY p; |
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register int i; |
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if (m->oargs.nfargs != (m->otype==MAT_DIELECTRIC ? 5 : 8)) |
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objerror(m, USER, "bad arguments"); |
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raytexture(r, m->omod); /* get modifiers */ |
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schorsch |
2.17 |
if ( (hastexture = DOT(r->pert,r->pert) > FTINY*FTINY) ) |
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gwlarson |
2.14 |
cos1 = raynormal(dnorm, r); /* perturb normal */ |
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else { |
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VCOPY(dnorm, r->ron); |
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cos1 = r->rod; |
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} |
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greg |
2.19 |
flatsurface = !hastexture && r->ro != NULL && isflat(r->ro->otype); |
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greg |
1.1 |
/* index of refraction */ |
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if (m->otype == MAT_DIELECTRIC) |
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nratio = m->oargs.farg[3] + m->oargs.farg[4]/MLAMBDA; |
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else |
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nratio = m->oargs.farg[3] / m->oargs.farg[7]; |
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105 |
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if (cos1 < 0.0) { /* inside */ |
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gwlarson |
2.14 |
hastexture = -hastexture; |
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greg |
1.1 |
cos1 = -cos1; |
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dnorm[0] = -dnorm[0]; |
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dnorm[1] = -dnorm[1]; |
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dnorm[2] = -dnorm[2]; |
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greg |
2.10 |
setcolor(r->cext, -mylog(m->oargs.farg[0]*colval(r->pcol,RED)), |
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-mylog(m->oargs.farg[1]*colval(r->pcol,GRN)), |
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-mylog(m->oargs.farg[2]*colval(r->pcol,BLU))); |
114 |
greg |
2.11 |
setcolor(r->albedo, 0., 0., 0.); |
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greg |
2.9 |
r->gecc = 0.; |
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if (m->otype == MAT_INTERFACE) { |
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setcolor(ctrans, |
118 |
greg |
2.10 |
-mylog(m->oargs.farg[4]*colval(r->pcol,RED)), |
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-mylog(m->oargs.farg[5]*colval(r->pcol,GRN)), |
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-mylog(m->oargs.farg[6]*colval(r->pcol,BLU))); |
121 |
greg |
2.11 |
setcolor(talb, 0., 0., 0.); |
122 |
greg |
2.9 |
} else { |
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copycolor(ctrans, cextinction); |
124 |
greg |
2.11 |
copycolor(talb, salbedo); |
125 |
greg |
2.9 |
} |
126 |
greg |
1.1 |
} else { /* outside */ |
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nratio = 1.0 / nratio; |
128 |
greg |
2.9 |
|
129 |
greg |
2.10 |
setcolor(ctrans, -mylog(m->oargs.farg[0]*colval(r->pcol,RED)), |
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-mylog(m->oargs.farg[1]*colval(r->pcol,GRN)), |
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-mylog(m->oargs.farg[2]*colval(r->pcol,BLU))); |
132 |
greg |
2.11 |
setcolor(talb, 0., 0., 0.); |
133 |
greg |
2.9 |
if (m->otype == MAT_INTERFACE) { |
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setcolor(r->cext, |
135 |
greg |
2.10 |
-mylog(m->oargs.farg[4]*colval(r->pcol,RED)), |
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-mylog(m->oargs.farg[5]*colval(r->pcol,GRN)), |
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-mylog(m->oargs.farg[6]*colval(r->pcol,BLU))); |
138 |
greg |
2.11 |
setcolor(r->albedo, 0., 0., 0.); |
139 |
greg |
2.9 |
r->gecc = 0.; |
140 |
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} |
141 |
greg |
1.1 |
} |
142 |
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143 |
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d2 = 1.0 - nratio*nratio*(1.0 - cos1*cos1); /* compute cos theta2 */ |
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145 |
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if (d2 < FTINY) /* total reflection */ |
146 |
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147 |
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refl = 1.0; |
148 |
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149 |
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else { /* refraction occurs */ |
150 |
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/* compute Fresnel's equations */ |
151 |
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cos2 = sqrt(d2); |
152 |
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d1 = cos1; |
153 |
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d2 = nratio*cos2; |
154 |
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d1 = (d1 - d2) / (d1 + d2); |
155 |
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refl = d1 * d1; |
156 |
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157 |
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d1 = 1.0 / cos1; |
158 |
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d2 = nratio / cos2; |
159 |
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d1 = (d1 - d2) / (d1 + d2); |
160 |
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refl += d1 * d1; |
161 |
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162 |
greg |
2.9 |
refl *= 0.5; |
163 |
greg |
1.1 |
trans = 1.0 - refl; |
164 |
greg |
2.15 |
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trans *= nratio*nratio; /* solid angle ratio */ |
166 |
greg |
1.1 |
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167 |
greg |
2.20 |
setcolor(p.rcoef, trans, trans, trans); |
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169 |
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if (rayorigin(&p, REFRACTED, r, p.rcoef) == 0) { |
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greg |
1.1 |
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/* compute refracted ray */ |
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d1 = nratio*cos1 - cos2; |
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for (i = 0; i < 3; i++) |
174 |
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p.rdir[i] = nratio*r->rdir[i] + d1*dnorm[i]; |
175 |
gwlarson |
2.14 |
/* accidental reflection? */ |
176 |
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if (hastexture && |
177 |
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DOT(p.rdir,r->ron)*hastexture >= -FTINY) { |
178 |
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d1 *= (double)hastexture; |
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for (i = 0; i < 3; i++) /* ignore texture */ |
180 |
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p.rdir[i] = nratio*r->rdir[i] + |
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d1*r->ron[i]; |
182 |
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normalize(p.rdir); /* not exact */ |
183 |
greg |
2.21 |
} else |
184 |
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checknorm(p.rdir); |
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greg |
1.1 |
#ifdef DISPERSE |
186 |
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if (m->otype != MAT_DIELECTRIC |
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|| r->rod > 0.0 |
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|| r->crtype & SHADOW |
189 |
greg |
2.3 |
|| !directvis |
190 |
greg |
1.1 |
|| m->oargs.farg[4] == 0.0 |
191 |
greg |
2.12 |
|| !disperse(m, r, p.rdir, |
192 |
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trans, ctrans, talb)) |
193 |
greg |
1.1 |
#endif |
194 |
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{ |
195 |
greg |
2.9 |
copycolor(p.cext, ctrans); |
196 |
greg |
2.11 |
copycolor(p.albedo, talb); |
197 |
greg |
1.1 |
rayvalue(&p); |
198 |
greg |
2.20 |
multcolor(p.rcol, p.rcoef); |
199 |
greg |
1.1 |
addcolor(r->rcol, p.rcol); |
200 |
greg |
2.19 |
/* virtual distance */ |
201 |
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if (flatsurface || |
202 |
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(1.-FTINY <= nratio && |
203 |
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nratio <= 1.+FTINY)) { |
204 |
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transtest = 2*bright(p.rcol); |
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transdist = r->rot + p.rt; |
206 |
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} |
207 |
greg |
1.1 |
} |
208 |
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} |
209 |
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} |
210 |
greg |
2.20 |
setcolor(p.rcoef, refl, refl, refl); |
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212 |
greg |
1.1 |
if (!(r->crtype & SHADOW) && |
213 |
greg |
2.20 |
rayorigin(&p, REFLECTED, r, p.rcoef) == 0) { |
214 |
greg |
1.1 |
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215 |
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/* compute reflected ray */ |
216 |
greg |
2.22 |
VSUM(p.rdir, r->rdir, dnorm, 2.*cos1); |
217 |
gwlarson |
2.14 |
/* accidental penetration? */ |
218 |
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if (hastexture && DOT(p.rdir,r->ron)*hastexture <= FTINY) |
219 |
greg |
2.22 |
VSUM(p.rdir, r->rdir, r->ron, 2.*r->rod); |
220 |
greg |
2.21 |
checknorm(p.rdir); |
221 |
greg |
1.1 |
rayvalue(&p); /* reflected ray value */ |
222 |
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223 |
greg |
2.20 |
multcolor(p.rcol, p.rcoef); /* color contribution */ |
224 |
greg |
1.1 |
addcolor(r->rcol, p.rcol); |
225 |
greg |
2.19 |
/* virtual distance */ |
226 |
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if (flatsurface) { |
227 |
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mirtest = 2*bright(p.rcol); |
228 |
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mirdist = r->rot + p.rt; |
229 |
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} |
230 |
greg |
1.1 |
} |
231 |
greg |
2.19 |
/* check distance to return */ |
232 |
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d1 = bright(r->rcol); |
233 |
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if (transtest > d1) |
234 |
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r->rt = transdist; |
235 |
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else if (mirtest > d1) |
236 |
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r->rt = mirdist; |
237 |
greg |
2.9 |
/* rayvalue() computes absorption */ |
238 |
greg |
2.7 |
return(1); |
239 |
greg |
1.1 |
} |
240 |
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241 |
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242 |
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#ifdef DISPERSE |
243 |
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244 |
schorsch |
2.18 |
static int |
245 |
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disperse( /* check light sources for dispersion */ |
246 |
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OBJREC *m, |
247 |
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RAY *r, |
248 |
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FVECT vt, |
249 |
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double tr, |
250 |
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COLOR cet, |
251 |
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COLOR abt |
252 |
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) |
253 |
greg |
1.1 |
{ |
254 |
greg |
2.20 |
RAY sray; |
255 |
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const RAY *entray; |
256 |
greg |
1.1 |
FVECT v1, v2, n1, n2; |
257 |
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FVECT dv, v2Xdv; |
258 |
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double v2Xdvv2Xdv; |
259 |
greg |
1.7 |
int success = 0; |
260 |
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SRCINDEX si; |
261 |
greg |
1.1 |
FVECT vtmp1, vtmp2; |
262 |
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double dtmp1, dtmp2; |
263 |
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int l1, l2; |
264 |
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COLOR ctmp; |
265 |
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int i; |
266 |
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267 |
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/* |
268 |
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* This routine computes dispersion to the first order using |
269 |
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* the following assumptions: |
270 |
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* |
271 |
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* 1) The dependency of the index of refraction on wavelength |
272 |
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* is approximated by Hartmann's equation with lambda0 |
273 |
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* equal to zero. |
274 |
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* 2) The entry and exit locations are constant with respect |
275 |
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* to dispersion. |
276 |
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* |
277 |
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* The second assumption permits us to model dispersion without |
278 |
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* having to sample refracted directions. We assume that the |
279 |
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* geometry inside the material is constant, and concern ourselves |
280 |
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* only with the relationship between the entering and exiting ray. |
281 |
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* We compute the first derivatives of the entering and exiting |
282 |
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* refraction with respect to the index of refraction. This |
283 |
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* is then used in a first order Taylor series to determine the |
284 |
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* index of refraction necessary to send the exiting ray to each |
285 |
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* light source. |
286 |
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* If an exiting ray hits a light source within the refraction |
287 |
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* boundaries, we sum all the frequencies over the disc of the |
288 |
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* light source to determine the resulting color. A smaller light |
289 |
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* source will therefore exhibit a sharper spectrum. |
290 |
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*/ |
291 |
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292 |
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if (!(r->crtype & REFRACTED)) { /* ray started in material */ |
293 |
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VCOPY(v1, r->rdir); |
294 |
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n1[0] = -r->rdir[0]; n1[1] = -r->rdir[1]; n1[2] = -r->rdir[2]; |
295 |
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} else { |
296 |
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/* find entry point */ |
297 |
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for (entray = r; entray->rtype != REFRACTED; |
298 |
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entray = entray->parent) |
299 |
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; |
300 |
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entray = entray->parent; |
301 |
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if (entray->crtype & REFRACTED) /* too difficult */ |
302 |
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return(0); |
303 |
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VCOPY(v1, entray->rdir); |
304 |
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VCOPY(n1, entray->ron); |
305 |
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} |
306 |
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VCOPY(v2, vt); /* exiting ray */ |
307 |
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VCOPY(n2, r->ron); |
308 |
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309 |
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/* first order dispersion approx. */ |
310 |
greg |
2.22 |
dtmp1 = 1./DOT(n1, v1); |
311 |
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dtmp2 = 1./DOT(n2, v2); |
312 |
greg |
1.1 |
for (i = 0; i < 3; i++) |
313 |
greg |
2.22 |
dv[i] = v1[i] + v2[i] - n1[i]*dtmp1 - n2[i]*dtmp2; |
314 |
greg |
1.1 |
|
315 |
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if (DOT(dv, dv) <= FTINY) /* null effect */ |
316 |
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return(0); |
317 |
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/* compute plane normal */ |
318 |
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fcross(v2Xdv, v2, dv); |
319 |
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v2Xdvv2Xdv = DOT(v2Xdv, v2Xdv); |
320 |
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321 |
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/* check sources */ |
322 |
greg |
1.7 |
initsrcindex(&si); |
323 |
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while (srcray(&sray, r, &si)) { |
324 |
greg |
1.1 |
|
325 |
greg |
1.7 |
if (DOT(sray.rdir, v2) < MINCOS) |
326 |
greg |
1.1 |
continue; /* bad source */ |
327 |
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/* adjust source ray */ |
328 |
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329 |
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dtmp1 = DOT(v2Xdv, sray.rdir) / v2Xdvv2Xdv; |
330 |
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sray.rdir[0] -= dtmp1 * v2Xdv[0]; |
331 |
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sray.rdir[1] -= dtmp1 * v2Xdv[1]; |
332 |
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sray.rdir[2] -= dtmp1 * v2Xdv[2]; |
333 |
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334 |
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l1 = lambda(m, v2, dv, sray.rdir); /* mean lambda */ |
335 |
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336 |
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if (l1 > MAXLAMBDA || l1 < MINLAMBDA) /* not visible */ |
337 |
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continue; |
338 |
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/* trace source ray */ |
339 |
greg |
2.12 |
copycolor(sray.cext, cet); |
340 |
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copycolor(sray.albedo, abt); |
341 |
greg |
1.1 |
normalize(sray.rdir); |
342 |
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rayvalue(&sray); |
343 |
greg |
1.2 |
if (bright(sray.rcol) <= FTINY) /* missed it */ |
344 |
greg |
1.1 |
continue; |
345 |
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346 |
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/* |
347 |
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* Compute spectral sum over diameter of source. |
348 |
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* First find directions for rays going to opposite |
349 |
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* sides of source, then compute wavelengths for each. |
350 |
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*/ |
351 |
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352 |
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fcross(vtmp1, v2Xdv, sray.rdir); |
353 |
greg |
1.7 |
dtmp1 = sqrt(si.dom / v2Xdvv2Xdv / PI); |
354 |
greg |
1.1 |
|
355 |
|
|
/* compute first ray */ |
356 |
greg |
2.22 |
VSUM(vtmp2, sray.rdir, vtmp1, dtmp1); |
357 |
greg |
1.1 |
|
358 |
|
|
l1 = lambda(m, v2, dv, vtmp2); /* first lambda */ |
359 |
|
|
if (l1 < 0) |
360 |
|
|
continue; |
361 |
|
|
/* compute second ray */ |
362 |
greg |
2.22 |
VSUM(vtmp2, sray.rdir, vtmp1, -dtmp1); |
363 |
greg |
1.1 |
|
364 |
|
|
l2 = lambda(m, v2, dv, vtmp2); /* second lambda */ |
365 |
|
|
if (l2 < 0) |
366 |
|
|
continue; |
367 |
|
|
/* compute color from spectrum */ |
368 |
|
|
if (l1 < l2) |
369 |
|
|
spec_rgb(ctmp, l1, l2); |
370 |
|
|
else |
371 |
|
|
spec_rgb(ctmp, l2, l1); |
372 |
|
|
multcolor(ctmp, sray.rcol); |
373 |
|
|
scalecolor(ctmp, tr); |
374 |
|
|
addcolor(r->rcol, ctmp); |
375 |
|
|
success++; |
376 |
|
|
} |
377 |
|
|
return(success); |
378 |
|
|
} |
379 |
|
|
|
380 |
|
|
|
381 |
|
|
static int |
382 |
schorsch |
2.18 |
lambda( /* compute lambda for material */ |
383 |
|
|
register OBJREC *m, |
384 |
|
|
FVECT v2, |
385 |
|
|
FVECT dv, |
386 |
|
|
FVECT lr |
387 |
|
|
) |
388 |
greg |
1.1 |
{ |
389 |
|
|
FVECT lrXdv, v2Xlr; |
390 |
|
|
double dtmp, denom; |
391 |
|
|
int i; |
392 |
|
|
|
393 |
|
|
fcross(lrXdv, lr, dv); |
394 |
|
|
for (i = 0; i < 3; i++) |
395 |
greg |
2.22 |
if ((lrXdv[i] > FTINY) | (lrXdv[i] < -FTINY)) |
396 |
greg |
1.1 |
break; |
397 |
|
|
if (i >= 3) |
398 |
|
|
return(-1); |
399 |
|
|
|
400 |
|
|
fcross(v2Xlr, v2, lr); |
401 |
|
|
|
402 |
|
|
dtmp = m->oargs.farg[4] / MLAMBDA; |
403 |
|
|
denom = dtmp + v2Xlr[i]/lrXdv[i] * (m->oargs.farg[3] + dtmp); |
404 |
|
|
|
405 |
|
|
if (denom < FTINY) |
406 |
|
|
return(-1); |
407 |
|
|
|
408 |
|
|
return(m->oargs.farg[4] / denom); |
409 |
|
|
} |
410 |
|
|
|
411 |
|
|
#endif /* DISPERSE */ |