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/* Copyright (c) 1990 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 for materials with arbitrary BRDF's |
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*/ |
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|
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#include "ray.h" |
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|
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#include "data.h" |
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|
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#include "otypes.h" |
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|
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/* |
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* Arguments to this material include the color and specularity. |
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* String arguments include the reflection function and files. |
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* The BRDF is currently used just for the specular component to light |
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* sources. Reflectance values or data coordinates are functions |
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* of the direction to the light source. |
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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_PFUNC and MAT_MFUNC are: |
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* 2+ func funcfile transform .. |
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* 0 |
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* 4+ red grn blu specularity args .. |
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* |
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* Arguments for MAT_PDATA and MAT_MDATA are: |
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* 4+ func datafile funcfile v0 .. transform .. |
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* 0 |
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* 4+ red grn blu specularity args .. |
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*/ |
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|
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extern double funvalue(), varvalue(); |
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|
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#define BSPEC(m) (6.0) /* specular parameter b */ |
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|
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typedef struct { |
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OBJREC *mp; /* material pointer */ |
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RAY *pr; /* intersected ray */ |
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DATARRAY *dp; /* data array for PDATA or MDATA */ |
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COLOR mcolor; /* color of this material */ |
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COLOR scolor; /* color of specular component */ |
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double rspec; /* specular reflection */ |
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double rdiff; /* diffuse reflection */ |
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FVECT pnorm; /* perturbed surface normal */ |
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double pdot; /* perturbed dot product */ |
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} BRDFDAT; /* BRDF material data */ |
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|
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|
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dirbrdf(cval, np, ldir, omega) /* compute source contribution */ |
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COLOR cval; /* returned coefficient */ |
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register BRDFDAT *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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double pt[MAXDIM]; |
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register int i; |
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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) |
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return; /* wrong side */ |
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|
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if (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 (np->rspec > FTINY) { |
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/* |
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* Compute specular component. |
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*/ |
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setfunc(np->mp, np->pr); |
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errno = 0; |
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if (np->dp == NULL) |
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dtmp = funvalue(np->mp->oargs.sarg[0], 3, ldir); |
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else { |
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for (i = 0; i < np->dp->nd; i++) |
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pt[i] = funvalue(np->mp->oargs.sarg[3+i], |
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3, ldir); |
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dtmp = datavalue(np->dp, pt); |
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dtmp = funvalue(np->mp->oargs.sarg[0], 1, &dtmp); |
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} |
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if (errno) |
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goto computerr; |
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if (dtmp > FTINY) { |
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copycolor(ctmp, np->scolor); |
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dtmp *= ldot * omega; |
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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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return; |
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computerr: |
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objerror(np->mp, WARNING, "compute error"); |
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return; |
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} |
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|
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|
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m_brdf(m, r) /* color a ray which hit a BRDF material */ |
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register OBJREC *m; |
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register RAY *r; |
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{ |
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BRDFDAT nd; |
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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.nsargs < 2 || m->oargs.nfargs < 4) |
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objerror(m, USER, "bad # arguments"); |
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/* easy shadow test */ |
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if (r->crtype & SHADOW) |
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return; |
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nd.mp = m; |
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nd.pr = r; |
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/* load auxiliary files */ |
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if (m->otype == MAT_PDATA || m->otype == MAT_MDATA) { |
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nd.dp = getdata(m->oargs.sarg[1]); |
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for (i = 3; i < m->oargs.nsargs; i++) |
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if (m->oargs.sarg[i][0] == '-') |
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break; |
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if (i-3 != nd.dp->nd) |
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objerror(m, USER, "dimension error"); |
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if (!fundefined(m->oargs.sarg[3])) |
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loadfunc(m->oargs.sarg[2]); |
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} else { |
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nd.dp = NULL; |
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if (!fundefined(m->oargs.sarg[0])) |
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loadfunc(m->oargs.sarg[1]); |
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} |
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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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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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multcolor(nd.mcolor, r->pcol); /* modify material color */ |
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r->rt = r->rot; /* default ray length */ |
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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_MFUNC || m->otype == MAT_MDATA) |
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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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/* diffuse reflection */ |
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nd.rdiff = 1.0 - nd.rspec; |
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/* compute ambient */ |
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if (nd.rdiff > FTINY) { |
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ambient(ctmp, r); |
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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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/* add direct component */ |
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direct(r, dirbrdf, &nd); |
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} |
