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1.1 |
#ifndef lint |
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2.22 |
static const char RCSid[] = "$Id: glass.c,v 2.21 2014/01/25 18:27:39 greg Exp $"; |
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1.1 |
#endif |
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/* |
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* glass.c - simpler shading function for thin glass surfaces. |
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*/ |
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2.11 |
#include "copyright.h" |
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1.1 |
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#include "ray.h" |
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2.8 |
#include "otypes.h" |
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2.15 |
#include "rtotypes.h" |
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2.8 |
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1.1 |
/* |
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* This definition of glass provides for a quick calculation |
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* using a single surface where two closely spaced parallel |
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* dielectric surfaces would otherwise be used. The chief |
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* advantage to using this material is speed, since internal |
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* reflections are avoided. |
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* |
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* The specification for glass is as follows: |
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* |
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* modifier glass id |
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* 0 |
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* 0 |
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2.9 |
* 3+ red grn blu [refractive_index] |
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1.1 |
* |
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* The color is used for the transmission at normal incidence. |
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* To compute transmissivity (tn) from transmittance (Tn) use: |
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1.1 |
* |
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* tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn |
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* |
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2.5 |
* The transmissivity of standard 88% transmittance glass is 0.96. |
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* A refractive index other than the default can be used by giving |
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* it as the fourth real argument. The above formula no longer applies. |
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* |
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1.1 |
* If we appear to hit the back side of the surface, then we |
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* turn the normal around. |
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*/ |
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#define RINDEX 1.52 /* refractive index of glass */ |
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2.22 |
int |
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2.15 |
m_glass( /* color a ray which hit a thin glass surface */ |
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OBJREC *m, |
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2.22 |
RAY *r |
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2.15 |
) |
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1.1 |
{ |
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COLOR mcolor; |
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double pdot; |
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FVECT pnorm; |
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2.20 |
double rindex=0, cos2; |
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1.1 |
COLOR trans, refl; |
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2.17 |
int hastexture, hastrans; |
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1.11 |
double d, r1e, r1m; |
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1.7 |
double transtest, transdist; |
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2.8 |
double mirtest, mirdist; |
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1.1 |
RAY p; |
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2.22 |
int i; |
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/* check arguments */ |
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if (m->oargs.nfargs == 3) |
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rindex = RINDEX; /* default value of n */ |
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else if (m->oargs.nfargs == 4) |
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rindex = m->oargs.farg[3]; /* use their value */ |
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else |
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1.1 |
objerror(m, USER, "bad arguments"); |
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2.21 |
/* check back face visibility */ |
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if (!backvis && r->rod <= 0.0) { |
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raytrans(r); |
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return(1); |
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} |
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2.17 |
/* check transmission */ |
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1.1 |
setcolor(mcolor, m->oargs.farg[0], m->oargs.farg[1], m->oargs.farg[2]); |
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2.17 |
if ((hastrans = (intens(mcolor) > 1e-15))) { |
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for (i = 0; i < 3; i++) |
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if (colval(mcolor,i) < 1e-15) |
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colval(mcolor,i) = 1e-15; |
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} else if (r->crtype & SHADOW) |
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return(1); |
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2.12 |
/* get modifiers */ |
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raytexture(r, m->omod); |
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1.1 |
if (r->rod < 0.0) /* reorient if necessary */ |
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flipsurface(r); |
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2.8 |
mirtest = transtest = 0; |
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mirdist = transdist = r->rot; |
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2.12 |
/* perturb normal */ |
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2.14 |
if ( (hastexture = (DOT(r->pert,r->pert) > FTINY*FTINY)) ) { |
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2.8 |
pdot = raynormal(pnorm, r); |
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2.13 |
} else { |
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2.8 |
VCOPY(pnorm, r->ron); |
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pdot = r->rod; |
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} |
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1.1 |
/* angular transmission */ |
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1.12 |
cos2 = sqrt( (1.0-1.0/(rindex*rindex)) + |
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pdot*pdot/(rindex*rindex) ); |
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if (hastrans) |
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setcolor(mcolor, pow(colval(mcolor,RED), 1.0/cos2), |
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pow(colval(mcolor,GRN), 1.0/cos2), |
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pow(colval(mcolor,BLU), 1.0/cos2)); |
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1.1 |
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/* compute reflection */ |
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1.12 |
r1e = (pdot - rindex*cos2) / (pdot + rindex*cos2); |
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1.11 |
r1e *= r1e; |
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1.12 |
r1m = (1.0/pdot - rindex/cos2) / (1.0/pdot + rindex/cos2); |
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1.11 |
r1m *= r1m; |
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2.17 |
/* compute transmission */ |
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if (hastrans) { |
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for (i = 0; i < 3; i++) { |
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d = colval(mcolor, i); |
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colval(trans,i) = .5*(1.0-r1e)*(1.0-r1e)*d / |
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(1.0-r1e*r1e*d*d); |
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colval(trans,i) += .5*(1.0-r1m)*(1.0-r1m)*d / |
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(1.0-r1m*r1m*d*d); |
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} |
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multcolor(trans, r->pcol); /* modify by pattern */ |
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1.1 |
/* transmitted ray */ |
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2.17 |
if (rayorigin(&p, TRANS, r, trans) == 0) { |
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2.22 |
if (!(r->crtype & (SHADOW|AMBIENT)) && hastexture) { |
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2.19 |
VSUM(p.rdir, r->rdir, r->pert, 2.*(1.-rindex)); |
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2.17 |
if (normalize(p.rdir) == 0.0) { |
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objerror(m, WARNING, "bad perturbation"); |
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VCOPY(p.rdir, r->rdir); |
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} |
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} else { |
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2.4 |
VCOPY(p.rdir, r->rdir); |
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2.17 |
transtest = 2; |
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2.4 |
} |
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2.17 |
rayvalue(&p); |
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multcolor(p.rcol, p.rcoef); |
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addcolor(r->rcol, p.rcol); |
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transtest *= bright(p.rcol); |
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transdist = r->rot + p.rt; |
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1.8 |
} |
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1.1 |
} |
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2.8 |
if (r->crtype & SHADOW) { /* skip reflected ray */ |
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r->rt = transdist; |
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2.7 |
return(1); |
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2.8 |
} |
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1.1 |
/* compute reflectance */ |
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for (i = 0; i < 3; i++) { |
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d = colval(mcolor, i); |
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d *= d; |
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1.11 |
colval(refl,i) = .5*r1e*(1.0+(1.0-2.0*r1e)*d)/(1.0-r1e*r1e*d); |
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colval(refl,i) += .5*r1m*(1.0+(1.0-2.0*r1m)*d)/(1.0-r1m*r1m*d); |
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1.1 |
} |
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/* reflected ray */ |
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2.16 |
if (rayorigin(&p, REFLECTED, r, refl) == 0) { |
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VSUM(p.rdir, r->rdir, pnorm, 2.*pdot); |
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checknorm(p.rdir); |
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1.1 |
rayvalue(&p); |
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multcolor(p.rcol, p.rcoef); |
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1.1 |
addcolor(r->rcol, p.rcol); |
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2.22 |
if (r->ro != NULL && isflat(r->ro->otype) && |
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!hastexture | (r->crtype & AMBIENT)) { |
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2.8 |
mirtest = 2.0*bright(p.rcol); |
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mirdist = r->rot + p.rt; |
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} |
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1.1 |
} |
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2.8 |
/* check distance */ |
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d = bright(r->rcol); |
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if (transtest > d) |
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1.7 |
r->rt = transdist; |
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2.8 |
else if (mirtest > d) |
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r->rt = mirdist; |
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2.7 |
return(1); |
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1.1 |
} |