src/rt/glass.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 *  glass.c - simpler shading function for thin glass surfaces.
 */

/* ====================================================================
 * The Radiance Software License, Version 1.0
 *
 * Copyright (c) 1990 - 2002 The Regents of the University of California,
 * through Lawrence Berkeley National Laboratory.   All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *         notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *           if any, must include the following acknowledgment:
 *             "This product includes Radiance software
 *                 (http://radsite.lbl.gov/)
 *                 developed by the Lawrence Berkeley National Laboratory
 *               (http://www.lbl.gov/)."
 *       Alternately, this acknowledgment may appear in the software itself,
 *       if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
 *       and "The Regents of the University of California" must
 *       not be used to endorse or promote products derived from this
 *       software without prior written permission. For written
 *       permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Radiance",
 *       nor may "Radiance" appear in their name, without prior written
 *       permission of Lawrence Berkeley National Laboratory.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.   IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Lawrence Berkeley National Laboratory.   For more
 * information on Lawrence Berkeley National Laboratory, please see
 * <http://www.lbl.gov/>.
 */

#include  "ray.h"

#include  "otypes.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 */


m_glass(m, r)           /* 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;
        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");

        setcolor(mcolor, m->oargs.farg[0], m->oargs.farg[1], m->oargs.farg[2]);

        if (r->rod < 0.0)                       /* reorient if necessary */
                flipsurface(r);
        mirtest = transtest = 0;
        mirdist = transdist = r->rot;
                                                /* get modifiers */
        raytexture(r, m->omod);
        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) );
        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 transmittance */
        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);
        }
                                                /* transmitted ray */
        if (rayorigin(&p, r, TRANS, bright(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, r->pcol);     /* modify */
                multcolor(p.rcol, trans);
                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, r, REFLECTED, bright(refl)) == 0) {
                for (i = 0; i < 3; i++)
                        p.rdir[i] = r->rdir[i] + 2.0*pdot*pnorm[i];
                rayvalue(&p);
                multcolor(p.rcol, refl);
                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:	2.10
Committed:	Sat Feb 22 02:07:28 2003 UTC (22 years, 8 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.9:	+57 -5 lines
Log Message:	Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.10	static const char RCSid[] = "$Id$";
3	greg	1.1	#endif
4			/*
5			* glass.c - simpler shading function for thin glass surfaces.
6	greg	2.10	*/
7
8			/* ====================================================================
9			* The Radiance Software License, Version 1.0
10			*
11			* Copyright (c) 1990 - 2002 The Regents of the University of California,
12			* through Lawrence Berkeley National Laboratory. All rights reserved.
13			*
14			* Redistribution and use in source and binary forms, with or without
15			* modification, are permitted provided that the following conditions
16			* are met:
17			*
18			* 1. Redistributions of source code must retain the above copyright
19			* notice, this list of conditions and the following disclaimer.
20			*
21			* 2. Redistributions in binary form must reproduce the above copyright
22			* notice, this list of conditions and the following disclaimer in
23			* the documentation and/or other materials provided with the
24			* distribution.
25			*
26			* 3. The end-user documentation included with the redistribution,
27			* if any, must include the following acknowledgment:
28			* "This product includes Radiance software
29			* (http://radsite.lbl.gov/)
30			* developed by the Lawrence Berkeley National Laboratory
31			* (http://www.lbl.gov/)."
32			* Alternately, this acknowledgment may appear in the software itself,
33			* if and wherever such third-party acknowledgments normally appear.
34			*
35			* 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
36			* and "The Regents of the University of California" must
37			* not be used to endorse or promote products derived from this
38			* software without prior written permission. For written
39			* permission, please contact [email protected].
40			*
41			* 5. Products derived from this software may not be called "Radiance",
42			* nor may "Radiance" appear in their name, without prior written
43			* permission of Lawrence Berkeley National Laboratory.
44			*
45			* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
46			* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
47			* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
48			* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
49			* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
50			* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
51			* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
52			* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
53			* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
54			* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
55			* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
56			* SUCH DAMAGE.
57			* ====================================================================
58	greg	1.1	*
59	greg	2.10	* This software consists of voluntary contributions made by many
60			* individuals on behalf of Lawrence Berkeley National Laboratory. For more
61			* information on Lawrence Berkeley National Laboratory, please see
62			* <http://www.lbl.gov/>.
63	greg	1.1	*/
64
65			#include "ray.h"
66
67	greg	2.8	#include "otypes.h"
68
69	greg	1.1	/*
70			* This definition of glass provides for a quick calculation
71			* using a single surface where two closely spaced parallel
72			* dielectric surfaces would otherwise be used. The chief
73			* advantage to using this material is speed, since internal
74			* reflections are avoided.
75			*
76			* The specification for glass is as follows:
77			*
78			* modifier glass id
79			* 0
80			* 0
81	greg	2.9	* 3+ red grn blu [refractive_index]
82	greg	1.1	*
83			* The color is used for the transmission at normal incidence.
84	greg	2.5	* To compute transmissivity (tn) from transmittance (Tn) use:
85	greg	1.1	*
86			* tn = (sqrt(.8402528435+.0072522239TnTn)-.9166530661)/.0036261119/Tn
87			*
88	greg	2.5	* The transmissivity of standard 88% transmittance glass is 0.96.
89	greg	1.12	* A refractive index other than the default can be used by giving
90			* it as the fourth real argument. The above formula no longer applies.
91			*
92	greg	1.1	* If we appear to hit the back side of the surface, then we
93			* turn the normal around.
94			*/
95
96			#define RINDEX 1.52 /* refractive index of glass */
97
98
99			m_glass(m, r) /* color a ray which hit a thin glass surface */
100			OBJREC *m;
101			register RAY *r;
102			{
103			COLOR mcolor;
104			double pdot;
105			FVECT pnorm;
106	greg	1.12	double rindex, cos2;
107	greg	1.1	COLOR trans, refl;
108	greg	2.8	int hastexture;
109	greg	1.11	double d, r1e, r1m;
110	greg	1.7	double transtest, transdist;
111	greg	2.8	double mirtest, mirdist;
112	greg	1.1	RAY p;
113			register int i;
114	greg	1.12	/* check arguments */
115			if (m->oargs.nfargs == 3)
116			rindex = RINDEX; /* default value of n */
117			else if (m->oargs.nfargs == 4)
118			rindex = m->oargs.farg[3]; /* use their value */
119			else
120	greg	1.1	objerror(m, USER, "bad arguments");
121
122			setcolor(mcolor, m->oargs.farg[0], m->oargs.farg[1], m->oargs.farg[2]);
123
124			if (r->rod < 0.0) /* reorient if necessary */
125			flipsurface(r);
126	greg	2.8	mirtest = transtest = 0;
127			mirdist = transdist = r->rot;
128	greg	1.1	/* get modifiers */
129			raytexture(r, m->omod);
130	greg	2.8	if (hastexture = DOT(r->pert,r->pert) > FTINY*FTINY)
131			pdot = raynormal(pnorm, r);
132			else {
133			VCOPY(pnorm, r->ron);
134			pdot = r->rod;
135			}
136	greg	1.1	/* angular transmission */
137	greg	1.12	cos2 = sqrt( (1.0-1.0/(rindex*rindex)) +
138			pdotpdot/(rindexrindex) );
139	greg	1.1	setcolor(mcolor, pow(colval(mcolor,RED), 1.0/cos2),
140			pow(colval(mcolor,GRN), 1.0/cos2),
141			pow(colval(mcolor,BLU), 1.0/cos2));
142
143			/* compute reflection */
144	greg	1.12	r1e = (pdot - rindexcos2) / (pdot + rindexcos2);
145	greg	1.11	r1e *= r1e;
146	greg	1.12	r1m = (1.0/pdot - rindex/cos2) / (1.0/pdot + rindex/cos2);
147	greg	1.11	r1m *= r1m;
148	greg	1.1	/* compute transmittance */
149			for (i = 0; i < 3; i++) {
150			d = colval(mcolor, i);
151	greg	1.11	colval(trans,i) = .5(1.0-r1e)(1.0-r1e)d/(1.0-r1er1edd);
152			colval(trans,i) += .5(1.0-r1m)(1.0-r1m)d/(1.0-r1mr1mdd);
153	greg	1.1	}
154			/* transmitted ray */
155	greg	1.2	if (rayorigin(&p, r, TRANS, bright(trans)) == 0) {
156	greg	2.8	if (!(r->crtype & SHADOW) && hastexture) {
157	greg	1.7	for (i = 0; i < 3; i++) /* perturb direction */
158	greg	2.2	p.rdir[i] = r->rdir[i] +
159			2.(1.-rindex)r->pert[i];
160	greg	2.4	if (normalize(p.rdir) == 0.0) {
161			objerror(m, WARNING, "bad perturbation");
162			VCOPY(p.rdir, r->rdir);
163			}
164	greg	1.8	} else {
165			VCOPY(p.rdir, r->rdir);
166	greg	1.7	transtest = 2;
167	greg	1.8	}
168	greg	1.1	rayvalue(&p);
169			multcolor(p.rcol, r->pcol); /* modify */
170			multcolor(p.rcol, trans);
171			addcolor(r->rcol, p.rcol);
172	greg	1.7	transtest *= bright(p.rcol);
173			transdist = r->rot + p.rt;
174	greg	1.1	}
175	greg	1.3
176	greg	2.8	if (r->crtype & SHADOW) { /* skip reflected ray */
177			r->rt = transdist;
178	greg	2.7	return(1);
179	greg	2.8	}
180	greg	1.1	/* compute reflectance */
181			for (i = 0; i < 3; i++) {
182			d = colval(mcolor, i);
183			d *= d;
184	greg	1.11	colval(refl,i) = .5r1e(1.0+(1.0-2.0r1e)d)/(1.0-r1er1ed);
185			colval(refl,i) += .5r1m(1.0+(1.0-2.0r1m)d)/(1.0-r1mr1md);
186	greg	1.1	}
187			/* reflected ray */
188	greg	1.2	if (rayorigin(&p, r, REFLECTED, bright(refl)) == 0) {
189	greg	1.1	for (i = 0; i < 3; i++)
190			p.rdir[i] = r->rdir[i] + 2.0pdotpnorm[i];
191			rayvalue(&p);
192			multcolor(p.rcol, refl);
193			addcolor(r->rcol, p.rcol);
194	greg	2.8	if (!hastexture && r->ro != NULL && isflat(r->ro->otype)) {
195			mirtest = 2.0*bright(p.rcol);
196			mirdist = r->rot + p.rt;
197			}
198	greg	1.1	}
199	greg	2.8	/* check distance */
200			d = bright(r->rcol);
201			if (transtest > d)
202	greg	1.7	r->rt = transdist;
203	greg	2.8	else if (mirtest > d)
204			r->rt = mirdist;
205	greg	2.7	return(1);
206	greg	1.1	}