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/* Copyright (c) 1991 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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* 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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*/ |
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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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/* |
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* This routine uses portions of the reflection |
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* model described by Cook and Torrance. |
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* The computation of specular components has been simplified by |
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* numerous approximations and ommisions to improve speed. |
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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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#define BSPEC(m) (6.0) /* specularity parameter b */ |
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|
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extern double exp(); |
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|
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typedef struct { |
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OBJREC *mp; /* material pointer */ |
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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 times 2 */ |
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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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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 dtmp; |
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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->rspec > FTINY && np->alpha2 > FTINY) { |
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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 + source */ |
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dtmp = np->alpha2 + omega/(2.0*PI); |
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/* gaussian */ |
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dtmp = exp((DOT(np->vrefl,ldir)-1.)/dtmp)/(2.*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 / 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->tspec > FTINY && np->alpha2 > FTINY) { |
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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/(2.0*PI); |
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/* gaussian */ |
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dtmp = exp((DOT(np->prdir,ldir)-1.)/dtmp)/(2.*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 / 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_normal(m, r) /* color a ray which 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 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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|
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if (m->oargs.nfargs != (m->otype == MAT_TRANS ? 7 : 5)) |
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objerror(m, USER, "bad # arguments"); |
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/* easy shadow test */ |
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if (r->crtype & SHADOW && m->otype != MAT_TRANS) |
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return; |
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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.alpha2 = m->oargs.farg[4]; |
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nd.alpha2 *= 2.0 * nd.alpha2; |
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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 dirnorm() */ |
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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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nd.rspec = m->oargs.farg[3]; |
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|
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if (nd.rspec > FTINY) { /* has specular component */ |
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/* compute specular color */ |
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if (m->otype == MAT_METAL) |
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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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/* compute reflected ray */ |
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for (i = 0; i < 3; i++) |
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nd.vrefl[i] = r->rdir[i] + 2.0*nd.pdot*nd.pnorm[i]; |
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|
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if (nd.alpha2 <= FTINY && !(r->crtype & SHADOW)) { |
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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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} |
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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[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 (r->crtype & SHADOW || 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 direction */ |
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nd.prdir[i] = r->rdir[i] - .75*r->pert[i]; |
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normalize(nd.prdir); |
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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.tspec > FTINY && nd.alpha2 <= FTINY) { |
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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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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.rdiff <= FTINY && nd.tdiff <= FTINY && nd.alpha2 <= FTINY) |
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return; /* purely specular */ |
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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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if (nd.alpha2 <= FTINY) |
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scalecolor(ctmp, nd.rdiff); |
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else |
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scalecolor(ctmp, 1.0-nd.trans); |
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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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if (nd.alpha2 <= FTINY) |
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scalecolor(ctmp, nd.tdiff); |
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else |
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scalecolor(ctmp, nd.trans); |
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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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if (transtest > bright(r->rcol)) |
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r->rt = transdist; |
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} |
