| 1 |
#ifndef lint |
| 2 |
static const char RCSid[] = "$Id: glass.c,v 1.4 2014/09/25 13:25:36 taschreg Exp taschreg $"; |
| 3 |
#endif |
| 4 |
/* |
| 5 |
* glass.c - simpler shading function for thin glass surfaces. |
| 6 |
*/ |
| 7 |
|
| 8 |
#include "copyright.h" |
| 9 |
|
| 10 |
#include "ray.h" |
| 11 |
#include "otypes.h" |
| 12 |
#include "rtotypes.h" |
| 13 |
#include "pmapmat.h" |
| 14 |
|
| 15 |
/* |
| 16 |
* This definition of glass provides for a quick calculation |
| 17 |
* using a single surface where two closely spaced parallel |
| 18 |
* dielectric surfaces would otherwise be used. The chief |
| 19 |
* advantage to using this material is speed, since internal |
| 20 |
* reflections are avoided. |
| 21 |
* |
| 22 |
* The specification for glass is as follows: |
| 23 |
* |
| 24 |
* modifier glass id |
| 25 |
* 0 |
| 26 |
* 0 |
| 27 |
* 3+ red grn blu [refractive_index] |
| 28 |
* |
| 29 |
* The color is used for the transmission at normal incidence. |
| 30 |
* To compute transmissivity (tn) from transmittance (Tn) use: |
| 31 |
* |
| 32 |
* tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn |
| 33 |
* |
| 34 |
* The transmissivity of standard 88% transmittance glass is 0.96. |
| 35 |
* A refractive index other than the default can be used by giving |
| 36 |
* it as the fourth real argument. The above formula no longer applies. |
| 37 |
* |
| 38 |
* If we appear to hit the back side of the surface, then we |
| 39 |
* turn the normal around. |
| 40 |
*/ |
| 41 |
|
| 42 |
#define RINDEX 1.52 /* refractive index of glass */ |
| 43 |
|
| 44 |
|
| 45 |
int |
| 46 |
m_glass( /* color a ray which hit a thin glass surface */ |
| 47 |
OBJREC *m, |
| 48 |
RAY *r |
| 49 |
) |
| 50 |
{ |
| 51 |
COLOR mcolor; |
| 52 |
double pdot; |
| 53 |
FVECT pnorm; |
| 54 |
double rindex=0, cos2; |
| 55 |
COLOR trans, refl; |
| 56 |
int hastexture, hastrans; |
| 57 |
double d, r1e, r1m; |
| 58 |
double transtest, transdist; |
| 59 |
double mirtest, mirdist; |
| 60 |
RAY p; |
| 61 |
int i; |
| 62 |
|
| 63 |
/* PMAP: skip refracted shadow ray if accounted for in photon map */ |
| 64 |
if (shadowRayInPmap(r)) |
| 65 |
return(1); |
| 66 |
/* check arguments */ |
| 67 |
if (m->oargs.nfargs == 3) |
| 68 |
rindex = RINDEX; /* default value of n */ |
| 69 |
else if (m->oargs.nfargs == 4) |
| 70 |
rindex = m->oargs.farg[3]; /* use their value */ |
| 71 |
else |
| 72 |
objerror(m, USER, "bad arguments"); |
| 73 |
/* check back face visibility */ |
| 74 |
if (!backvis && r->rod <= 0.0) { |
| 75 |
raytrans(r); |
| 76 |
return(1); |
| 77 |
} |
| 78 |
/* check transmission */ |
| 79 |
setcolor(mcolor, m->oargs.farg[0], m->oargs.farg[1], m->oargs.farg[2]); |
| 80 |
if ((hastrans = (intens(mcolor) > 1e-15))) { |
| 81 |
for (i = 0; i < 3; i++) |
| 82 |
if (colval(mcolor,i) < 1e-15) |
| 83 |
colval(mcolor,i) = 1e-15; |
| 84 |
} else if (r->crtype & SHADOW) |
| 85 |
return(1); |
| 86 |
/* get modifiers */ |
| 87 |
raytexture(r, m->omod); |
| 88 |
if (r->rod < 0.0) /* reorient if necessary */ |
| 89 |
flipsurface(r); |
| 90 |
mirtest = transtest = 0; |
| 91 |
mirdist = transdist = r->rot; |
| 92 |
/* perturb normal */ |
| 93 |
if ( (hastexture = (DOT(r->pert,r->pert) > FTINY*FTINY)) ) { |
| 94 |
pdot = raynormal(pnorm, r); |
| 95 |
} else { |
| 96 |
VCOPY(pnorm, r->ron); |
| 97 |
pdot = r->rod; |
| 98 |
} |
| 99 |
/* angular transmission */ |
| 100 |
cos2 = sqrt( (1.0-1.0/(rindex*rindex)) + |
| 101 |
pdot*pdot/(rindex*rindex) ); |
| 102 |
if (hastrans) |
| 103 |
setcolor(mcolor, pow(colval(mcolor,RED), 1.0/cos2), |
| 104 |
pow(colval(mcolor,GRN), 1.0/cos2), |
| 105 |
pow(colval(mcolor,BLU), 1.0/cos2)); |
| 106 |
|
| 107 |
/* compute reflection */ |
| 108 |
r1e = (pdot - rindex*cos2) / (pdot + rindex*cos2); |
| 109 |
r1e *= r1e; |
| 110 |
r1m = (1.0/pdot - rindex/cos2) / (1.0/pdot + rindex/cos2); |
| 111 |
r1m *= r1m; |
| 112 |
/* compute transmission */ |
| 113 |
if (hastrans) { |
| 114 |
for (i = 0; i < 3; i++) { |
| 115 |
d = colval(mcolor, i); |
| 116 |
colval(trans,i) = .5*(1.0-r1e)*(1.0-r1e)*d / |
| 117 |
(1.0-r1e*r1e*d*d); |
| 118 |
colval(trans,i) += .5*(1.0-r1m)*(1.0-r1m)*d / |
| 119 |
(1.0-r1m*r1m*d*d); |
| 120 |
} |
| 121 |
multcolor(trans, r->pcol); /* modify by pattern */ |
| 122 |
/* transmitted ray */ |
| 123 |
if (rayorigin(&p, TRANS, r, trans) == 0) { |
| 124 |
if (!(r->crtype & (SHADOW|AMBIENT)) && hastexture) { |
| 125 |
VSUM(p.rdir, r->rdir, r->pert, 2.*(1.-rindex)); |
| 126 |
if (normalize(p.rdir) == 0.0) { |
| 127 |
objerror(m, WARNING, "bad perturbation"); |
| 128 |
VCOPY(p.rdir, r->rdir); |
| 129 |
} |
| 130 |
} else { |
| 131 |
VCOPY(p.rdir, r->rdir); |
| 132 |
transtest = 2; |
| 133 |
} |
| 134 |
rayvalue(&p); |
| 135 |
multcolor(p.rcol, p.rcoef); |
| 136 |
addcolor(r->rcol, p.rcol); |
| 137 |
transtest *= bright(p.rcol); |
| 138 |
transdist = r->rot + p.rt; |
| 139 |
} |
| 140 |
} |
| 141 |
if (r->crtype & SHADOW) { /* skip reflected ray */ |
| 142 |
r->rt = transdist; |
| 143 |
return(1); |
| 144 |
} |
| 145 |
/* compute reflectance */ |
| 146 |
for (i = 0; i < 3; i++) { |
| 147 |
d = colval(mcolor, i); |
| 148 |
d *= d; |
| 149 |
colval(refl,i) = .5*r1e*(1.0+(1.0-2.0*r1e)*d)/(1.0-r1e*r1e*d); |
| 150 |
colval(refl,i) += .5*r1m*(1.0+(1.0-2.0*r1m)*d)/(1.0-r1m*r1m*d); |
| 151 |
} |
| 152 |
/* reflected ray */ |
| 153 |
if (rayorigin(&p, REFLECTED, r, refl) == 0) { |
| 154 |
VSUM(p.rdir, r->rdir, pnorm, 2.*pdot); |
| 155 |
checknorm(p.rdir); |
| 156 |
rayvalue(&p); |
| 157 |
multcolor(p.rcol, p.rcoef); |
| 158 |
addcolor(r->rcol, p.rcol); |
| 159 |
if (r->ro != NULL && isflat(r->ro->otype) && |
| 160 |
!hastexture | (r->crtype & AMBIENT)) { |
| 161 |
mirtest = 2.0*bright(p.rcol); |
| 162 |
mirdist = r->rot + p.rt; |
| 163 |
} |
| 164 |
} |
| 165 |
/* check distance */ |
| 166 |
d = bright(r->rcol); |
| 167 |
if (transtest > d) |
| 168 |
r->rt = transdist; |
| 169 |
else if (mirtest > d) |
| 170 |
r->rt = mirdist; |
| 171 |
return(1); |
| 172 |
} |
