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greg |
1.1 |
/* Copyright (c) 1990 Regents of the University of California */
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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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* Shading for materials with arbitrary BRDF's
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*/
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#include "ray.h"
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#include "data.h"
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#include "otypes.h"
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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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greg |
1.2 |
extern double funvalue(), varvalue();
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greg |
1.1 |
#define BSPEC(m) (6.0) /* specular parameter b */
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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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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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setcolor(cval, 0.0, 0.0, 0.0);
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ldot = DOT(np->pnorm, ldir);
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if (ldot < 0.0)
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return; /* wrong side */
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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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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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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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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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}
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