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#ifndef lint |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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* normal.c - shading function for normal materials. |
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* |
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* 8/19/85 |
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* 12/19/85 - added stuff for metals. |
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* 6/26/87 - improved specular model. |
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* 9/28/87 - added model for translucent materials. |
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* Later changes described in delta comments. |
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*/ |
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|
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#include "copyright.h" |
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|
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#include "ray.h" |
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|
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#include "otypes.h" |
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|
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#include "random.h" |
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|
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#ifndef MAXITER |
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#define MAXITER 10 /* maximum # specular ray attempts */ |
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#endif |
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/* estimate of Fresnel function */ |
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#define FRESNE(ci) (exp(-6.0*(ci)) - 0.00247875217) |
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|
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static void gaussamp(); |
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|
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/* |
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* This routine implements the isotropic Gaussian |
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* model described by Ward in Siggraph `92 article. |
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* We orient the surface towards the incoming ray, so a single |
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* surface can be used to represent an infinitely thin object. |
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* |
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* Arguments for MAT_PLASTIC and MAT_METAL are: |
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* red grn blu specular-frac. facet-slope |
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* |
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* Arguments for MAT_TRANS are: |
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* red grn blu rspec rough trans tspec |
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*/ |
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|
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/* specularity flags */ |
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#define SP_REFL 01 /* has reflected specular component */ |
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#define SP_TRAN 02 /* has transmitted specular */ |
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#define SP_PURE 04 /* purely specular (zero roughness) */ |
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#define SP_FLAT 010 /* flat reflecting surface */ |
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#define SP_RBLT 020 /* reflection below sample threshold */ |
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#define SP_TBLT 040 /* transmission below threshold */ |
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|
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typedef struct { |
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OBJREC *mp; /* material pointer */ |
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RAY *rp; /* ray pointer */ |
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short specfl; /* specularity flags, defined above */ |
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COLOR mcolor; /* color of this material */ |
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COLOR scolor; /* color of specular component */ |
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FVECT vrefl; /* vector in direction of reflected ray */ |
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FVECT prdir; /* vector in transmitted direction */ |
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double alpha2; /* roughness squared */ |
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double rdiff, rspec; /* reflected specular, diffuse */ |
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double trans; /* transmissivity */ |
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double tdiff, tspec; /* transmitted specular, diffuse */ |
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FVECT pnorm; /* perturbed surface normal */ |
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double pdot; /* perturbed dot product */ |
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} NORMDAT; /* normal material data */ |
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|
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|
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static void |
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dirnorm(cval, np, ldir, omega) /* compute source contribution */ |
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COLOR cval; /* returned coefficient */ |
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register NORMDAT *np; /* material data */ |
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FVECT ldir; /* light source direction */ |
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double omega; /* light source size */ |
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{ |
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double ldot; |
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double ldiff; |
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double dtmp, d2; |
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FVECT vtmp; |
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COLOR ctmp; |
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|
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setcolor(cval, 0.0, 0.0, 0.0); |
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|
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ldot = DOT(np->pnorm, ldir); |
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|
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if (ldot < 0.0 ? np->trans <= FTINY : np->trans >= 1.0-FTINY) |
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return; /* wrong side */ |
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|
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/* Fresnel estimate */ |
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ldiff = np->rdiff; |
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if (np->specfl & SP_PURE && (np->rspec > FTINY & ldiff > FTINY)) |
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ldiff *= 1. - FRESNE(fabs(ldot)); |
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|
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if (ldot > FTINY && ldiff > FTINY) { |
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/* |
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* Compute and add diffuse reflected component to returned |
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* color. The diffuse reflected component will always be |
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* modified by the color of the material. |
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*/ |
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copycolor(ctmp, np->mcolor); |
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dtmp = ldot * omega * ldiff / PI; |
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scalecolor(ctmp, dtmp); |
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addcolor(cval, ctmp); |
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} |
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if (ldot > FTINY && (np->specfl&(SP_REFL|SP_PURE)) == SP_REFL) { |
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/* |
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* Compute specular reflection coefficient using |
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* gaussian distribution model. |
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*/ |
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/* roughness */ |
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dtmp = np->alpha2; |
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/* + source if flat */ |
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if (np->specfl & SP_FLAT) |
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dtmp += omega/(4.0*PI); |
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/* half vector */ |
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vtmp[0] = ldir[0] - np->rp->rdir[0]; |
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vtmp[1] = ldir[1] - np->rp->rdir[1]; |
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vtmp[2] = ldir[2] - np->rp->rdir[2]; |
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d2 = DOT(vtmp, np->pnorm); |
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d2 *= d2; |
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d2 = (DOT(vtmp,vtmp) - d2) / d2; |
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/* gaussian */ |
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dtmp = exp(-d2/dtmp)/(4.*PI*dtmp); |
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/* worth using? */ |
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if (dtmp > FTINY) { |
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copycolor(ctmp, np->scolor); |
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dtmp *= omega * sqrt(ldot/np->pdot); |
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scalecolor(ctmp, dtmp); |
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addcolor(cval, ctmp); |
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} |
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} |
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if (ldot < -FTINY && np->tdiff > FTINY) { |
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/* |
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* Compute diffuse transmission. |
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*/ |
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copycolor(ctmp, np->mcolor); |
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dtmp = -ldot * omega * np->tdiff / PI; |
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scalecolor(ctmp, dtmp); |
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addcolor(cval, ctmp); |
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} |
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if (ldot < -FTINY && (np->specfl&(SP_TRAN|SP_PURE)) == SP_TRAN) { |
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/* |
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* Compute specular transmission. Specular transmission |
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* is always modified by material color. |
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*/ |
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/* roughness + source */ |
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dtmp = np->alpha2 + omega/PI; |
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/* gaussian */ |
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dtmp = exp((2.*DOT(np->prdir,ldir)-2.)/dtmp)/(PI*dtmp); |
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/* worth using? */ |
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if (dtmp > FTINY) { |
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copycolor(ctmp, np->mcolor); |
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dtmp *= np->tspec * omega * sqrt(-ldot/np->pdot); |
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scalecolor(ctmp, dtmp); |
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addcolor(cval, ctmp); |
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} |
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} |
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} |
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|
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|
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int |
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m_normal(m, r) /* color a ray that hit something normal */ |
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register OBJREC *m; |
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register RAY *r; |
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{ |
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NORMDAT nd; |
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double fest; |
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double transtest, transdist; |
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double mirtest, mirdist; |
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int hastexture; |
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double d; |
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COLOR ctmp; |
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register int i; |
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/* easy shadow test */ |
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if (r->crtype & SHADOW && m->otype != MAT_TRANS) |
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return(1); |
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|
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if (m->oargs.nfargs != (m->otype == MAT_TRANS ? 7 : 5)) |
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objerror(m, USER, "bad number of arguments"); |
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/* check for back side */ |
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if (r->rod < 0.0) { |
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if (!backvis && m->otype != MAT_TRANS) { |
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raytrans(r); |
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return(1); |
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} |
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raytexture(r, m->omod); |
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flipsurface(r); /* reorient if backvis */ |
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} else |
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raytexture(r, m->omod); |
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nd.mp = m; |
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nd.rp = r; |
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/* get material color */ |
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setcolor(nd.mcolor, m->oargs.farg[0], |
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m->oargs.farg[1], |
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m->oargs.farg[2]); |
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/* get roughness */ |
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nd.specfl = 0; |
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nd.alpha2 = m->oargs.farg[4]; |
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if ((nd.alpha2 *= nd.alpha2) <= FTINY) |
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nd.specfl |= SP_PURE; |
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if (r->ro != NULL && isflat(r->ro->otype)) |
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nd.specfl |= SP_FLAT; |
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|
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if (hastexture = DOT(r->pert,r->pert) > FTINY*FTINY) |
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nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */ |
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else { |
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VCOPY(nd.pnorm, r->ron); |
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nd.pdot = r->rod; |
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} |
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if (nd.pdot < .001) |
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nd.pdot = .001; /* non-zero for dirnorm() */ |
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multcolor(nd.mcolor, r->pcol); /* modify material color */ |
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mirtest = transtest = 0; |
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mirdist = transdist = r->rot; |
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nd.rspec = m->oargs.farg[3]; |
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/* compute Fresnel approx. */ |
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if (nd.specfl & SP_PURE && nd.rspec > FTINY) { |
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fest = FRESNE(r->rod); |
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nd.rspec += fest*(1. - nd.rspec); |
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} else |
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fest = 0.; |
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/* compute transmission */ |
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if (m->otype == MAT_TRANS) { |
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nd.trans = m->oargs.farg[5]*(1.0 - nd.rspec); |
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nd.tspec = nd.trans * m->oargs.farg[6]; |
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nd.tdiff = nd.trans - nd.tspec; |
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if (nd.tspec > FTINY) { |
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nd.specfl |= SP_TRAN; |
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/* check threshold */ |
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if (!(nd.specfl & SP_PURE) && |
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specthresh >= nd.tspec-FTINY) |
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nd.specfl |= SP_TBLT; |
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if (!hastexture || r->crtype & SHADOW) { |
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VCOPY(nd.prdir, r->rdir); |
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transtest = 2; |
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} else { |
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for (i = 0; i < 3; i++) /* perturb */ |
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nd.prdir[i] = r->rdir[i] - r->pert[i]; |
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if (DOT(nd.prdir, r->ron) < -FTINY) |
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normalize(nd.prdir); /* OK */ |
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else |
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VCOPY(nd.prdir, r->rdir); |
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} |
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} |
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} else |
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nd.tdiff = nd.tspec = nd.trans = 0.0; |
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/* transmitted ray */ |
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if ((nd.specfl&(SP_TRAN|SP_PURE|SP_TBLT)) == (SP_TRAN|SP_PURE)) { |
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RAY lr; |
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if (rayorigin(&lr, r, TRANS, nd.tspec) == 0) { |
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VCOPY(lr.rdir, nd.prdir); |
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rayvalue(&lr); |
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scalecolor(lr.rcol, nd.tspec); |
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multcolor(lr.rcol, nd.mcolor); /* modified by color */ |
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addcolor(r->rcol, lr.rcol); |
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transtest *= bright(lr.rcol); |
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transdist = r->rot + lr.rt; |
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} |
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} else |
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transtest = 0; |
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|
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if (r->crtype & SHADOW) { /* the rest is shadow */ |
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r->rt = transdist; |
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return(1); |
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} |
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/* get specular reflection */ |
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if (nd.rspec > FTINY) { |
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nd.specfl |= SP_REFL; |
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/* compute specular color */ |
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if (m->otype != MAT_METAL) { |
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setcolor(nd.scolor, nd.rspec, nd.rspec, nd.rspec); |
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} else if (fest > FTINY) { |
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d = nd.rspec*(1. - fest); |
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for (i = 0; i < 3; i++) |
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nd.scolor[i] = fest + nd.mcolor[i]*d; |
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} else { |
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copycolor(nd.scolor, nd.mcolor); |
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scalecolor(nd.scolor, nd.rspec); |
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} |
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/* check threshold */ |
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if (!(nd.specfl & SP_PURE) && specthresh >= nd.rspec-FTINY) |
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nd.specfl |= SP_RBLT; |
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/* compute reflected ray */ |
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for (i = 0; i < 3; i++) |
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nd.vrefl[i] = r->rdir[i] + 2.*nd.pdot*nd.pnorm[i]; |
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/* penetration? */ |
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if (hastexture && DOT(nd.vrefl, r->ron) <= FTINY) |
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for (i = 0; i < 3; i++) /* safety measure */ |
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nd.vrefl[i] = r->rdir[i] + 2.*r->rod*r->ron[i]; |
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} |
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/* reflected ray */ |
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if ((nd.specfl&(SP_REFL|SP_PURE|SP_RBLT)) == (SP_REFL|SP_PURE)) { |
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RAY lr; |
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if (rayorigin(&lr, r, REFLECTED, nd.rspec) == 0) { |
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VCOPY(lr.rdir, nd.vrefl); |
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rayvalue(&lr); |
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multcolor(lr.rcol, nd.scolor); |
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addcolor(r->rcol, lr.rcol); |
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if (!hastexture && nd.specfl & SP_FLAT) { |
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mirtest = 2.*bright(lr.rcol); |
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mirdist = r->rot + lr.rt; |
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} |
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} |
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} |
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/* diffuse reflection */ |
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nd.rdiff = 1.0 - nd.trans - nd.rspec; |
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|
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if (nd.specfl & SP_PURE && nd.rdiff <= FTINY && nd.tdiff <= FTINY) |
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return(1); /* 100% pure specular */ |
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|
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if (!(nd.specfl & SP_PURE)) |
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gaussamp(r, &nd); /* checks *BLT flags */ |
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|
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if (nd.rdiff > FTINY) { /* ambient from this side */ |
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ambient(ctmp, r, hastexture?nd.pnorm:r->ron); |
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if (nd.specfl & SP_RBLT) |
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scalecolor(ctmp, 1.0-nd.trans); |
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else |
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scalecolor(ctmp, nd.rdiff); |
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multcolor(ctmp, nd.mcolor); /* modified by material color */ |
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addcolor(r->rcol, ctmp); /* add to returned color */ |
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} |
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if (nd.tdiff > FTINY) { /* ambient from other side */ |
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flipsurface(r); |
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if (hastexture) { |
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FVECT bnorm; |
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bnorm[0] = -nd.pnorm[0]; |
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bnorm[1] = -nd.pnorm[1]; |
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bnorm[2] = -nd.pnorm[2]; |
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ambient(ctmp, r, bnorm); |
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} else |
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ambient(ctmp, r, r->ron); |
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if (nd.specfl & SP_TBLT) |
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scalecolor(ctmp, nd.trans); |
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else |
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scalecolor(ctmp, nd.tdiff); |
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multcolor(ctmp, nd.mcolor); /* modified by color */ |
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addcolor(r->rcol, ctmp); |
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flipsurface(r); |
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} |
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/* add direct component */ |
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direct(r, dirnorm, &nd); |
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/* check distance */ |
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d = bright(r->rcol); |
344 |
if (transtest > d) |
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r->rt = transdist; |
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else if (mirtest > d) |
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r->rt = mirdist; |
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|
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return(1); |
350 |
} |
351 |
|
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|
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static void |
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gaussamp(r, np) /* sample gaussian specular */ |
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RAY *r; |
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register NORMDAT *np; |
357 |
{ |
358 |
RAY sr; |
359 |
FVECT u, v, h; |
360 |
double rv[2]; |
361 |
double d, sinp, cosp; |
362 |
int niter; |
363 |
register int i; |
364 |
/* quick test */ |
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if ((np->specfl & (SP_REFL|SP_RBLT)) != SP_REFL && |
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(np->specfl & (SP_TRAN|SP_TBLT)) != SP_TRAN) |
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return; |
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/* set up sample coordinates */ |
369 |
v[0] = v[1] = v[2] = 0.0; |
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for (i = 0; i < 3; i++) |
371 |
if (np->pnorm[i] < 0.6 && np->pnorm[i] > -0.6) |
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break; |
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v[i] = 1.0; |
374 |
fcross(u, v, np->pnorm); |
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normalize(u); |
376 |
fcross(v, np->pnorm, u); |
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/* compute reflection */ |
378 |
if ((np->specfl & (SP_REFL|SP_RBLT)) == SP_REFL && |
379 |
rayorigin(&sr, r, SPECULAR, np->rspec) == 0) { |
380 |
dimlist[ndims++] = (int)np->mp; |
381 |
for (niter = 0; niter < MAXITER; niter++) { |
382 |
if (niter) |
383 |
d = frandom(); |
384 |
else |
385 |
d = urand(ilhash(dimlist,ndims)+samplendx); |
386 |
multisamp(rv, 2, d); |
387 |
d = 2.0*PI * rv[0]; |
388 |
cosp = tcos(d); |
389 |
sinp = tsin(d); |
390 |
rv[1] = 1.0 - specjitter*rv[1]; |
391 |
if (rv[1] <= FTINY) |
392 |
d = 1.0; |
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else |
394 |
d = sqrt( np->alpha2 * -log(rv[1]) ); |
395 |
for (i = 0; i < 3; i++) |
396 |
h[i] = np->pnorm[i] + d*(cosp*u[i] + sinp*v[i]); |
397 |
d = -2.0 * DOT(h, r->rdir) / (1.0 + d*d); |
398 |
for (i = 0; i < 3; i++) |
399 |
sr.rdir[i] = r->rdir[i] + d*h[i]; |
400 |
if (DOT(sr.rdir, r->ron) > FTINY) { |
401 |
rayvalue(&sr); |
402 |
multcolor(sr.rcol, np->scolor); |
403 |
addcolor(r->rcol, sr.rcol); |
404 |
break; |
405 |
} |
406 |
} |
407 |
ndims--; |
408 |
} |
409 |
/* compute transmission */ |
410 |
if ((np->specfl & (SP_TRAN|SP_TBLT)) == SP_TRAN && |
411 |
rayorigin(&sr, r, SPECULAR, np->tspec) == 0) { |
412 |
dimlist[ndims++] = (int)np->mp; |
413 |
for (niter = 0; niter < MAXITER; niter++) { |
414 |
if (niter) |
415 |
d = frandom(); |
416 |
else |
417 |
d = urand(ilhash(dimlist,ndims)+1823+samplendx); |
418 |
multisamp(rv, 2, d); |
419 |
d = 2.0*PI * rv[0]; |
420 |
cosp = tcos(d); |
421 |
sinp = tsin(d); |
422 |
rv[1] = 1.0 - specjitter*rv[1]; |
423 |
if (rv[1] <= FTINY) |
424 |
d = 1.0; |
425 |
else |
426 |
d = sqrt( np->alpha2 * -log(rv[1]) ); |
427 |
for (i = 0; i < 3; i++) |
428 |
sr.rdir[i] = np->prdir[i] + d*(cosp*u[i] + sinp*v[i]); |
429 |
if (DOT(sr.rdir, r->ron) < -FTINY) { |
430 |
normalize(sr.rdir); /* OK, normalize */ |
431 |
rayvalue(&sr); |
432 |
scalecolor(sr.rcol, np->tspec); |
433 |
multcolor(sr.rcol, np->mcolor); /* modified */ |
434 |
addcolor(r->rcol, sr.rcol); |
435 |
break; |
436 |
} |
437 |
} |
438 |
ndims--; |
439 |
} |
440 |
} |