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/* Copyright (c) 1992 Regents of the University of California */ |
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|
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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#endif |
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|
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/* |
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* Shading functions for anisotropic materials. |
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*/ |
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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 "func.h" |
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|
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#include "random.h" |
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|
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/* |
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* This anisotropic reflection model uses a variant on the |
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* exponential Gaussian used in normal.c. |
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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_PLASTIC2 and MAT_METAL2 are: |
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* 4+ ux uy uz funcfile [transform...] |
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* 0 |
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* 6 red grn blu specular-frac. u-facet-slope v-facet-slope |
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* |
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* Real arguments for MAT_TRANS2 are: |
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* 8 red grn blu rspec u-rough v-rough trans tspec |
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*/ |
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|
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#define BSPEC(m) (6.0) /* specularity parameter b */ |
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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 010 /* purely specular (zero roughness) */ |
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#define SP_BADU 020 /* bad u direction calculation */ |
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|
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typedef struct { |
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RAY *rp; /* ray pointer */ |
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OBJREC *mp; /* material 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 prdir; /* vector in transmitted direction */ |
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FVECT u, v; /* u and v vectors orienting anisotropy */ |
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double u_alpha; /* u roughness */ |
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double v_alpha; /* v roughness */ |
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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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} ANISODAT; /* anisotropic material data */ |
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|
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|
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diraniso(cval, np, ldir, omega) /* compute source contribution */ |
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COLOR cval; /* returned coefficient */ |
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register ANISODAT *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 dtmp, dtmp2; |
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FVECT h; |
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double au2, av2; |
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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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if (ldot > FTINY && np->rdiff > 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 * np->rdiff / 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_BADU)) == SP_REFL) { |
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/* |
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* Compute specular reflection coefficient using |
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* anisotropic gaussian distribution model. |
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*/ |
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/* roughness + source */ |
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au2 = av2 = omega/(4.0*PI); |
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au2 += np->u_alpha * np->u_alpha; |
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av2 += np->v_alpha * np->v_alpha; |
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/* half vector */ |
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h[0] = ldir[0] - np->rp->rdir[0]; |
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h[1] = ldir[1] - np->rp->rdir[1]; |
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h[2] = ldir[2] - np->rp->rdir[2]; |
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normalize(h); |
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/* ellipse */ |
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dtmp = DOT(np->u, h); |
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dtmp *= dtmp / au2; |
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dtmp2 = DOT(np->v, h); |
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dtmp2 *= dtmp2 / av2; |
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/* gaussian */ |
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dtmp = (dtmp + dtmp2) / (1.0 + DOT(np->pnorm, h)); |
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dtmp = exp(-2.0*dtmp) / (4.0*PI * sqrt(au2*av2)); |
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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 / 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_BADU)) == 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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/* gaussian */ |
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dtmp = 0.0; |
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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 / 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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m_aniso(m, r) /* shade ray that hit something anisotropic */ |
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register OBJREC *m; |
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register RAY *r; |
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{ |
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ANISODAT nd; |
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double transtest, transdist; |
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double dtmp; |
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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_TRANS2) |
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return; |
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|
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if (m->oargs.nfargs != (m->otype == MAT_TRANS2 ? 8 : 6)) |
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objerror(m, USER, "bad number of real arguments"); |
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nd.rp = r; |
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nd.mp = m; |
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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.u_alpha = m->oargs.farg[4]; |
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nd.v_alpha = m->oargs.farg[5]; |
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if (nd.u_alpha <= FTINY || nd.v_alpha <= FTINY) |
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nd.specfl |= SP_PURE; |
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/* reorient if necessary */ |
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if (r->rod < 0.0) |
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flipsurface(r); |
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/* get modifiers */ |
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raytexture(r, m->omod); |
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nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */ |
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if (nd.pdot < .001) |
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nd.pdot = .001; /* non-zero for diraniso() */ |
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multcolor(nd.mcolor, r->pcol); /* modify material color */ |
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transtest = 0; |
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/* get specular component */ |
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if ((nd.rspec = m->oargs.farg[3]) > FTINY) { |
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nd.specfl |= SP_REFL; |
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/* compute specular color */ |
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if (m->otype == MAT_METAL2) |
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copycolor(nd.scolor, nd.mcolor); |
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else |
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setcolor(nd.scolor, 1.0, 1.0, 1.0); |
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scalecolor(nd.scolor, nd.rspec); |
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/* improved model */ |
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dtmp = exp(-BSPEC(m)*nd.pdot); |
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for (i = 0; i < 3; i++) |
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colval(nd.scolor,i) += (1.0-colval(nd.scolor,i))*dtmp; |
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nd.rspec += (1.0-nd.rspec)*dtmp; |
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|
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if (!(r->crtype & SHADOW) && nd.specfl & SP_PURE) { |
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RAY lr; |
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if (rayorigin(&lr, r, REFLECTED, nd.rspec) == 0) { |
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for (i = 0; i < 3; i++) |
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lr.rdir[i] = r->rdir[i] + |
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2.0*nd.pdot*nd.pnorm[i]; |
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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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} |
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} |
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} |
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/* compute transmission */ |
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if (m->otype == MAT_TRANS) { |
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nd.trans = m->oargs.farg[6]*(1.0 - nd.rspec); |
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nd.tspec = nd.trans * m->oargs.farg[7]; |
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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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if (r->crtype & SHADOW || |
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DOT(r->pert,r->pert) <= FTINY*FTINY) { |
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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] - |
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.75*r->pert[i]; |
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normalize(nd.prdir); |
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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_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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} |
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|
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if (r->crtype & SHADOW) /* the rest is shadow */ |
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return; |
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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; /* 100% pure specular */ |
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|
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getacoords(r, &nd); /* set up coordinates */ |
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|
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if (nd.specfl & (SP_REFL|SP_TRAN) && !(nd.specfl & (SP_PURE|SP_BADU))) |
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agaussamp(r, &nd); |
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|
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if (nd.rdiff > FTINY) { /* ambient from this side */ |
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ambient(ctmp, r); |
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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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ambient(ctmp, r); |
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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, diraniso, &nd); |
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/* check distance */ |
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if (transtest > bright(r->rcol)) |
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r->rt = transdist; |
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} |
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|
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|
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static |
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getacoords(r, np) /* set up coordinate system */ |
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RAY *r; |
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register ANISODAT *np; |
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{ |
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register MFUNC *mf; |
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register int i; |
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|
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mf = getfunc(np->mp, 3, 0x7, 1); |
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setfunc(np->mp, r); |
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errno = 0; |
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for (i = 0; i < 3; i++) |
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np->u[i] = evalue(mf->ep[i]); |
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if (errno) { |
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objerror(np->mp, WARNING, "compute error"); |
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np->specfl |= SP_BADU; |
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return; |
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} |
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multv3(np->u, np->u, mf->f->xfm); |
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fcross(np->v, np->pnorm, np->u); |
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if (normalize(np->v) == 0.0) { |
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objerror(np->mp, WARNING, "illegal orientation vector"); |
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np->specfl |= SP_BADU; |
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return; |
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} |
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fcross(np->u, np->v, np->pnorm); |
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} |
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|
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|
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static |
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agaussamp(r, np) /* sample anisotropic gaussian specular */ |
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RAY *r; |
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register ANISODAT *np; |
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{ |
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RAY sr; |
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FVECT h; |
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double rv[2]; |
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double d, sinp, cosp; |
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int confuse; |
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register int i; |
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/* compute reflection */ |
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if (np->specfl & SP_REFL && |
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rayorigin(&sr, r, SPECULAR, np->rspec) == 0) { |
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confuse = 0; |
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dimlist[ndims++] = (int)np->mp; |
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refagain: |
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dimlist[ndims] = confuse += 3601; |
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d = urand(ilhash(dimlist,ndims+1)+samplendx); |
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multisamp(rv, 2, d); |
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d = 2.0*PI * rv[0]; |
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cosp = np->u_alpha * cos(d); |
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sinp = np->v_alpha * sin(d); |
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d = sqrt(cosp*cosp + sinp*sinp); |
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cosp /= d; |
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sinp /= d; |
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if (rv[1] <= FTINY) |
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d = 1.0; |
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else |
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d = sqrt( -log(rv[1]) / |
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(cosp*cosp/(np->u_alpha*np->u_alpha) + |
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sinp*sinp/(np->v_alpha*np->v_alpha)) ); |
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for (i = 0; i < 3; i++) |
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h[i] = np->pnorm[i] + |
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d*(cosp*np->u[i] + sinp*np->v[i]); |
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d = -2.0 * DOT(h, r->rdir) / (1.0 + d*d); |
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for (i = 0; i < 3; i++) |
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sr.rdir[i] = r->rdir[i] + d*h[i]; |
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if (DOT(sr.rdir, r->ron) <= FTINY) /* oops! */ |
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goto refagain; |
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rayvalue(&sr); |
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multcolor(sr.rcol, np->scolor); |
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addcolor(r->rcol, sr.rcol); |
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ndims--; |
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} |
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/* compute transmission */ |
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} |
