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/* Copyright (c) 1998 Silicon Graphics, Inc. */ |
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#ifndef lint |
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static char SCCSid[] = "$SunId$ SGI"; |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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* dielectric.c - shading function for transparent materials. |
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*/ |
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/* ==================================================================== |
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* The Radiance Software License, Version 1.0 |
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* |
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* 9/6/85 |
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* Copyright (c) 1990 - 2002 The Regents of the University of California, |
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* through Lawrence Berkeley National Laboratory. All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in |
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* the documentation and/or other materials provided with the |
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* distribution. |
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* |
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* 3. The end-user documentation included with the redistribution, |
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* if any, must include the following acknowledgment: |
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* "This product includes Radiance software |
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* (http://radsite.lbl.gov/) |
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* developed by the Lawrence Berkeley National Laboratory |
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* (http://www.lbl.gov/)." |
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* Alternately, this acknowledgment may appear in the software itself, |
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* if and wherever such third-party acknowledgments normally appear. |
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* |
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* 4. The names "Radiance," "Lawrence Berkeley National Laboratory" |
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* and "The Regents of the University of California" must |
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* not be used to endorse or promote products derived from this |
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* software without prior written permission. For written |
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* permission, please contact [email protected]. |
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* |
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* 5. Products derived from this software may not be called "Radiance", |
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* nor may "Radiance" appear in their name, without prior written |
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* permission of Lawrence Berkeley National Laboratory. |
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* |
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
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* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR |
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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* SUCH DAMAGE. |
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* ==================================================================== |
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* |
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* This software consists of voluntary contributions made by many |
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* individuals on behalf of Lawrence Berkeley National Laboratory. For more |
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* information on Lawrence Berkeley National Laboratory, please see |
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* <http://www.lbl.gov/>. |
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*/ |
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#include "ray.h" |
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#define MINCOS 0.997 /* minimum dot product for dispersion */ |
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extern COLOR cextinction; /* global coefficient of extinction */ |
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extern COLOR salbedo; /* global scattering albedo */ |
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static double |
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mylog(x) /* special log for extinction coefficients */ |
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double x; |
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double cos1, cos2, nratio; |
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COLOR ctrans; |
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COLOR talb; |
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int hastexture; |
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double refl, trans; |
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FVECT dnorm; |
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double d1, d2; |
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raytexture(r, m->omod); /* get modifiers */ |
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cos1 = raynormal(dnorm, r); /* cosine of theta1 */ |
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if (hastexture = DOT(r->pert,r->pert) > FTINY*FTINY) |
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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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/* 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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nratio = m->oargs.farg[3] / m->oargs.farg[7]; |
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if (cos1 < 0.0) { /* inside */ |
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hastexture = -hastexture; |
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cos1 = -cos1; |
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dnorm[0] = -dnorm[0]; |
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dnorm[1] = -dnorm[1]; |
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refl *= 0.5; |
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trans = 1.0 - refl; |
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trans *= nratio*nratio; /* solid angle ratio */ |
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if (rayorigin(&p, r, REFRACTED, trans) == 0) { |
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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++) |
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p.rdir[i] = nratio*r->rdir[i] + d1*dnorm[i]; |
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/* accidental reflection? */ |
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if (hastexture && |
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DOT(p.rdir,r->ron)*hastexture >= -FTINY) { |
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d1 *= (double)hastexture; |
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for (i = 0; i < 3; i++) /* ignore texture */ |
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p.rdir[i] = nratio*r->rdir[i] + |
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d1*r->ron[i]; |
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normalize(p.rdir); /* not exact */ |
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} |
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#ifdef DISPERSE |
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if (m->otype != MAT_DIELECTRIC |
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|| r->rod > 0.0 |
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/* compute reflected ray */ |
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for (i = 0; i < 3; i++) |
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p.rdir[i] = r->rdir[i] + 2.0*cos1*dnorm[i]; |
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/* accidental penetration? */ |
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if (hastexture && DOT(p.rdir,r->ron)*hastexture <= FTINY) |
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for (i = 0; i < 3; i++) /* ignore texture */ |
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p.rdir[i] = r->rdir[i] + 2.0*r->rod*r->ron[i]; |
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rayvalue(&p); /* reflected ray value */ |
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