src/rt/glass.c

#ifndef lint
static const char RCSid[] = "$Id: glass.c,v 2.16 2005/04/19 01:15:06 greg Exp $";
#endif
/*
 *  glass.c - simpler shading function for thin glass surfaces.
 */

#include "copyright.h"

#include  "ray.h"
#include  "otypes.h"
#include  "rtotypes.h"

/*
 *  This definition of glass provides for a quick calculation
 *  using a single surface where two closely spaced parallel
 *  dielectric surfaces would otherwise be used.  The chief
 *  advantage to using this material is speed, since internal
 *  reflections are avoided.
 *
 *  The specification for glass is as follows:
 *
 *      modifier glass id
 *      0
 *      0
 *      3+ red grn blu [refractive_index]
 *
 *  The color is used for the transmission at normal incidence.
 *  To compute transmissivity (tn) from transmittance (Tn) use:
 *
 *      tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn
 *
 *  The transmissivity of standard 88% transmittance glass is 0.96.
 *  A refractive index other than the default can be used by giving
 *  it as the fourth real argument.  The above formula no longer applies.
 *
 *  If we appear to hit the back side of the surface, then we
 *  turn the normal around.
 */

#define  RINDEX         1.52            /* refractive index of glass */


extern int
m_glass(                /* color a ray which hit a thin glass surface */
        OBJREC  *m,
        register RAY  *r
)
{
        COLOR  mcolor;
        double  pdot;
        FVECT  pnorm;
        double  rindex, cos2;
        COLOR  trans, refl;
        int  hastexture, hastrans;
        double  d, r1e, r1m;
        double  transtest, transdist;
        double  mirtest, mirdist;
        RAY  p;
        register int  i;
                                                /* check arguments */
        if (m->oargs.nfargs == 3)
                rindex = RINDEX;                /* default value of n */
        else if (m->oargs.nfargs == 4)
                rindex = m->oargs.farg[3];      /* use their value */
        else
                objerror(m, USER, "bad arguments");
                                                /* check transmission */
        setcolor(mcolor, m->oargs.farg[0], m->oargs.farg[1], m->oargs.farg[2]);
        if ((hastrans = (intens(mcolor) > 1e-15))) {
                for (i = 0; i < 3; i++)
                        if (colval(mcolor,i) < 1e-15)
                                colval(mcolor,i) = 1e-15;
        } else if (r->crtype & SHADOW)
                return(1);
                                                /* get modifiers */
        raytexture(r, m->omod);
        if (r->rod < 0.0)                       /* reorient if necessary */
                flipsurface(r);
        mirtest = transtest = 0;
        mirdist = transdist = r->rot;
                                                /* perturb normal */
        if ( (hastexture = (DOT(r->pert,r->pert) > FTINY*FTINY)) ) {
                pdot = raynormal(pnorm, r);
        } else {
                VCOPY(pnorm, r->ron);
                pdot = r->rod;
        }
                                                /* angular transmission */
        cos2 = sqrt( (1.0-1.0/(rindex*rindex)) +
                     pdot*pdot/(rindex*rindex) );
        if (hastrans)
                setcolor(mcolor, pow(colval(mcolor,RED), 1.0/cos2),
                                 pow(colval(mcolor,GRN), 1.0/cos2),
                                 pow(colval(mcolor,BLU), 1.0/cos2));

                                                /* compute reflection */
        r1e = (pdot - rindex*cos2) / (pdot + rindex*cos2);
        r1e *= r1e;
        r1m = (1.0/pdot - rindex/cos2) / (1.0/pdot + rindex/cos2);
        r1m *= r1m;
                                                /* compute transmission */
        if (hastrans) {
                for (i = 0; i < 3; i++) {
                        d = colval(mcolor, i);
                        colval(trans,i) = .5*(1.0-r1e)*(1.0-r1e)*d /
                                                        (1.0-r1e*r1e*d*d);
                        colval(trans,i) += .5*(1.0-r1m)*(1.0-r1m)*d /
                                                        (1.0-r1m*r1m*d*d);
                }
                multcolor(trans, r->pcol);      /* modify by pattern */
                                                /* transmitted ray */
                if (rayorigin(&p, TRANS, r, trans) == 0) {
                        if (!(r->crtype & SHADOW) && hastexture) {
                                for (i = 0; i < 3; i++) /* perturb direction */
                                        p.rdir[i] = r->rdir[i] +
                                                2.*(1.-rindex)*r->pert[i];
                                if (normalize(p.rdir) == 0.0) {
                                        objerror(m, WARNING, "bad perturbation");
                                        VCOPY(p.rdir, r->rdir);
                                }
                        } else {
                                VCOPY(p.rdir, r->rdir);
                                transtest = 2;
                        }
                        rayvalue(&p);
                        multcolor(p.rcol, p.rcoef);
                        addcolor(r->rcol, p.rcol);
                        transtest *= bright(p.rcol);
                        transdist = r->rot + p.rt;
                }
        }
        if (r->crtype & SHADOW) {               /* skip reflected ray */
                r->rt = transdist;
                return(1);
        }
                                                /* compute reflectance */
        for (i = 0; i < 3; i++) {
                d = colval(mcolor, i);
                d *= d;
                colval(refl,i) = .5*r1e*(1.0+(1.0-2.0*r1e)*d)/(1.0-r1e*r1e*d);
                colval(refl,i) += .5*r1m*(1.0+(1.0-2.0*r1m)*d)/(1.0-r1m*r1m*d);
        }
                                                /* reflected ray */
        if (rayorigin(&p, REFLECTED, r, refl) == 0) {
                for (i = 0; i < 3; i++)
                        p.rdir[i] = r->rdir[i] + 2.0*pdot*pnorm[i];
                rayvalue(&p);
                multcolor(p.rcol, p.rcoef);
                addcolor(r->rcol, p.rcol);
                if (!hastexture && r->ro != NULL && isflat(r->ro->otype)) {
                        mirtest = 2.0*bright(p.rcol);
                        mirdist = r->rot + p.rt;
                }
        }
                                        /* check distance */
        d = bright(r->rcol);
        if (transtest > d)
                r->rt = transdist;
        else if (mirtest > d)
                r->rt = mirdist;
        return(1);
}
Revision:	2.17
Committed:	Tue Jun 21 15:06:50 2005 UTC (18 years, 10 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad3R7P2, rad3R7P1, rad4R0, rad3R8, rad3R9
Changes since 2.16:	+38 -29 lines
Log Message:	Fixed bugs in black glass transmission and source weight computation
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.17	static const char RCSid[] = "$Id: glass.c,v 2.16 2005/04/19 01:15:06 greg Exp $";
3	greg	1.1	#endif
4			/*
5			* glass.c - simpler shading function for thin glass surfaces.
6	greg	2.10	*/
7
8	greg	2.11	#include "copyright.h"
9	greg	1.1
10			#include "ray.h"
11	greg	2.8	#include "otypes.h"
12	schorsch	2.15	#include "rtotypes.h"
13	greg	2.8
14	greg	1.1	/*
15			* This definition of glass provides for a quick calculation
16			* using a single surface where two closely spaced parallel
17			* dielectric surfaces would otherwise be used. The chief
18			* advantage to using this material is speed, since internal
19			* reflections are avoided.
20			*
21			* The specification for glass is as follows:
22			*
23			* modifier glass id
24			* 0
25			* 0
26	greg	2.9	* 3+ red grn blu [refractive_index]
27	greg	1.1	*
28			* The color is used for the transmission at normal incidence.
29	greg	2.5	* To compute transmissivity (tn) from transmittance (Tn) use:
30	greg	1.1	*
31			* tn = (sqrt(.8402528435+.0072522239TnTn)-.9166530661)/.0036261119/Tn
32			*
33	greg	2.5	* The transmissivity of standard 88% transmittance glass is 0.96.
34	greg	1.12	* A refractive index other than the default can be used by giving
35			* it as the fourth real argument. The above formula no longer applies.
36			*
37	greg	1.1	* If we appear to hit the back side of the surface, then we
38			* turn the normal around.
39			*/
40
41			#define RINDEX 1.52 /* refractive index of glass */
42
43
44	schorsch	2.15	extern int
45			m_glass( /* color a ray which hit a thin glass surface */
46			OBJREC *m,
47			register RAY *r
48			)
49	greg	1.1	{
50			COLOR mcolor;
51			double pdot;
52			FVECT pnorm;
53	greg	1.12	double rindex, cos2;
54	greg	1.1	COLOR trans, refl;
55	greg	2.17	int hastexture, hastrans;
56	greg	1.11	double d, r1e, r1m;
57	greg	1.7	double transtest, transdist;
58	greg	2.8	double mirtest, mirdist;
59	greg	1.1	RAY p;
60			register int i;
61	greg	1.12	/* check arguments */
62			if (m->oargs.nfargs == 3)
63			rindex = RINDEX; /* default value of n */
64			else if (m->oargs.nfargs == 4)
65			rindex = m->oargs.farg[3]; /* use their value */
66			else
67	greg	1.1	objerror(m, USER, "bad arguments");
68	greg	2.17	/* check transmission */
69	greg	1.1	setcolor(mcolor, m->oargs.farg[0], m->oargs.farg[1], m->oargs.farg[2]);
70	greg	2.17	if ((hastrans = (intens(mcolor) > 1e-15))) {
71			for (i = 0; i < 3; i++)
72			if (colval(mcolor,i) < 1e-15)
73			colval(mcolor,i) = 1e-15;
74			} else if (r->crtype & SHADOW)
75			return(1);
76	greg	2.12	/* get modifiers */
77			raytexture(r, m->omod);
78	greg	1.1	if (r->rod < 0.0) /* reorient if necessary */
79			flipsurface(r);
80	greg	2.8	mirtest = transtest = 0;
81			mirdist = transdist = r->rot;
82	greg	2.12	/* perturb normal */
83	schorsch	2.14	if ( (hastexture = (DOT(r->pert,r->pert) > FTINY*FTINY)) ) {
84	greg	2.8	pdot = raynormal(pnorm, r);
85	greg	2.13	} else {
86	greg	2.8	VCOPY(pnorm, r->ron);
87			pdot = r->rod;
88			}
89	greg	1.1	/* angular transmission */
90	greg	1.12	cos2 = sqrt( (1.0-1.0/(rindex*rindex)) +
91			pdotpdot/(rindexrindex) );
92	greg	2.17	if (hastrans)
93			setcolor(mcolor, pow(colval(mcolor,RED), 1.0/cos2),
94			pow(colval(mcolor,GRN), 1.0/cos2),
95			pow(colval(mcolor,BLU), 1.0/cos2));
96	greg	1.1
97			/* compute reflection */
98	greg	1.12	r1e = (pdot - rindexcos2) / (pdot + rindexcos2);
99	greg	1.11	r1e *= r1e;
100	greg	1.12	r1m = (1.0/pdot - rindex/cos2) / (1.0/pdot + rindex/cos2);
101	greg	1.11	r1m *= r1m;
102	greg	2.17	/* compute transmission */
103			if (hastrans) {
104			for (i = 0; i < 3; i++) {
105			d = colval(mcolor, i);
106			colval(trans,i) = .5(1.0-r1e)(1.0-r1e)*d /
107			(1.0-r1er1ed*d);
108			colval(trans,i) += .5(1.0-r1m)(1.0-r1m)*d /
109			(1.0-r1mr1md*d);
110			}
111			multcolor(trans, r->pcol); /* modify by pattern */
112	greg	1.1	/* transmitted ray */
113	greg	2.17	if (rayorigin(&p, TRANS, r, trans) == 0) {
114			if (!(r->crtype & SHADOW) && hastexture) {
115			for (i = 0; i < 3; i++) /* perturb direction */
116			p.rdir[i] = r->rdir[i] +
117	greg	2.2	2.(1.-rindex)r->pert[i];
118	greg	2.17	if (normalize(p.rdir) == 0.0) {
119			objerror(m, WARNING, "bad perturbation");
120			VCOPY(p.rdir, r->rdir);
121			}
122			} else {
123	greg	2.4	VCOPY(p.rdir, r->rdir);
124	greg	2.17	transtest = 2;
125	greg	2.4	}
126	greg	2.17	rayvalue(&p);
127			multcolor(p.rcol, p.rcoef);
128			addcolor(r->rcol, p.rcol);
129			transtest *= bright(p.rcol);
130			transdist = r->rot + p.rt;
131	greg	1.8	}
132	greg	1.1	}
133	greg	2.8	if (r->crtype & SHADOW) { /* skip reflected ray */
134			r->rt = transdist;
135	greg	2.7	return(1);
136	greg	2.8	}
137	greg	1.1	/* compute reflectance */
138			for (i = 0; i < 3; i++) {
139			d = colval(mcolor, i);
140			d *= d;
141	greg	1.11	colval(refl,i) = .5r1e(1.0+(1.0-2.0r1e)d)/(1.0-r1er1ed);
142			colval(refl,i) += .5r1m(1.0+(1.0-2.0r1m)d)/(1.0-r1mr1md);
143	greg	1.1	}
144			/* reflected ray */
145	greg	2.16	if (rayorigin(&p, REFLECTED, r, refl) == 0) {
146	greg	1.1	for (i = 0; i < 3; i++)
147			p.rdir[i] = r->rdir[i] + 2.0pdotpnorm[i];
148			rayvalue(&p);
149	greg	2.16	multcolor(p.rcol, p.rcoef);
150	greg	1.1	addcolor(r->rcol, p.rcol);
151	greg	2.8	if (!hastexture && r->ro != NULL && isflat(r->ro->otype)) {
152			mirtest = 2.0*bright(p.rcol);
153			mirdist = r->rot + p.rt;
154			}
155	greg	1.1	}
156	greg	2.8	/* check distance */
157			d = bright(r->rcol);
158			if (transtest > d)
159	greg	1.7	r->rt = transdist;
160	greg	2.8	else if (mirtest > d)
161			r->rt = mirdist;
162	greg	2.7	return(1);
163	greg	1.1	}