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Fri, Nov 8, 03:04

normal.c
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#ifndef lint
static const char RCSid[] = "$Id: normal.c,v 2.80 2019/04/19 19:01:32 greg Exp $";
#endif
/*
* normal.c - shading function for normal materials.
*
* 8/19/85
* 12/19/85 - added stuff for metals.
* 6/26/87 - improved specular model.
* 9/28/87 - added model for translucent materials.
* Later changes described in delta comments.
*/
#include "copyright.h"
#include "ray.h"
#include "ambient.h"
#include "source.h"
#include "otypes.h"
#include "rtotypes.h"
#include "random.h"
#include "pmapmat.h"
#ifndef MAXITER
#define MAXITER 10 /* maximum # specular ray attempts */
#endif
/* estimate of Fresnel function */
#define FRESNE(ci) (exp(-5.85*(ci)) - 0.00287989916)
#define FRESTHRESH 0.017999 /* minimum specularity for approx. */
/*
* This routine implements the isotropic Gaussian
* model described by Ward in Siggraph `92 article.
* We orient the surface towards the incoming ray, so a single
* surface can be used to represent an infinitely thin object.
*
* Arguments for MAT_PLASTIC and MAT_METAL are:
* red grn blu specular-frac. facet-slope
*
* Arguments for MAT_TRANS are:
* red grn blu rspec rough trans tspec
*/
/* specularity flags */
#define SP_REFL 01 /* has reflected specular component */
#define SP_TRAN 02 /* has transmitted specular */
#define SP_PURE 04 /* purely specular (zero roughness) */
#define SP_FLAT 010 /* flat reflecting surface */
#define SP_RBLT 020 /* reflection below sample threshold */
#define SP_TBLT 040 /* transmission below threshold */
typedef struct {
OBJREC *mp; /* material pointer */
RAY *rp; /* ray pointer */
short specfl; /* specularity flags, defined above */
COLOR mcolor; /* color of this material */
COLOR scolor; /* color of specular component */
FVECT vrefl; /* vector in direction of reflected ray */
FVECT prdir; /* vector in transmitted direction */
double alpha2; /* roughness squared */
double rdiff, rspec; /* reflected specular, diffuse */
double trans; /* transmissivity */
double tdiff, tspec; /* transmitted specular, diffuse */
FVECT pnorm; /* perturbed surface normal */
double pdot; /* perturbed dot product */
} NORMDAT; /* normal material data */
static void gaussamp(NORMDAT *np);
static void
dirnorm( /* compute source contribution */
COLOR cval, /* returned coefficient */
void *nnp, /* material data */
FVECT ldir, /* light source direction */
double omega /* light source size */
)
{
NORMDAT *np = nnp;
double ldot;
double lrdiff, ltdiff;
double dtmp, d2, d3, d4;
FVECT vtmp;
COLOR ctmp;
setcolor(cval, 0.0, 0.0, 0.0);
ldot = DOT(np->pnorm, ldir);
if (ldot < 0.0 ? np->trans <= FTINY : np->trans >= 1.0-FTINY)
return; /* wrong side */
/* Fresnel estimate */
lrdiff = np->rdiff;
ltdiff = np->tdiff;
if (np->specfl & SP_PURE && np->rspec >= FRESTHRESH &&
(lrdiff > FTINY) | (ltdiff > FTINY)) {
dtmp = 1. - FRESNE(fabs(ldot));
lrdiff *= dtmp;
ltdiff *= dtmp;
}
if (ldot > FTINY && lrdiff > FTINY) {
/*
* Compute and add diffuse reflected component to returned
* color. The diffuse reflected component will always be
* modified by the color of the material.
*/
copycolor(ctmp, np->mcolor);
dtmp = ldot * omega * lrdiff * (1.0/PI);
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
if (ldot < -FTINY && ltdiff > FTINY) {
/*
* Compute diffuse transmission.
*/
copycolor(ctmp, np->mcolor);
dtmp = -ldot * omega * ltdiff * (1.0/PI);
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
if (ambRayInPmap(np->rp))
return; /* specular already in photon map */
if (ldot > FTINY && (np->specfl&(SP_REFL|SP_PURE)) == SP_REFL) {
/*
* Compute specular reflection coefficient using
* Gaussian distribution model.
*/
/* roughness */
dtmp = np->alpha2;
/* + source if flat */
if (np->specfl & SP_FLAT)
dtmp += omega * (0.25/PI);
/* half vector */
VSUB(vtmp, ldir, np->rp->rdir);
d2 = DOT(vtmp, np->pnorm);
d2 *= d2;
d3 = DOT(vtmp,vtmp);
d4 = (d3 - d2) / d2;
/* new W-G-M-D model */
dtmp = exp(-d4/dtmp) * d3 / (PI * d2*d2 * dtmp);
/* worth using? */
if (dtmp > FTINY) {
copycolor(ctmp, np->scolor);
dtmp *= ldot * omega;
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
}
if (ldot < -FTINY && (np->specfl&(SP_TRAN|SP_PURE)) == SP_TRAN) {
/*
* Compute specular transmission. Specular transmission
* is always modified by material color.
*/
/* roughness + source */
dtmp = np->alpha2 + omega*(1.0/PI);
/* Gaussian */
dtmp = exp((2.*DOT(np->prdir,ldir)-2.)/dtmp)/(PI*dtmp);
/* worth using? */
if (dtmp > FTINY) {
copycolor(ctmp, np->mcolor);
dtmp *= np->tspec * omega * sqrt(-ldot/np->pdot);
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
}
}
int
m_normal( /* color a ray that hit something normal */
OBJREC *m,
RAY *r
)
{
NORMDAT nd;
double fest;
int hastexture;
double d;
COLOR ctmp;
int i;
/* PMAP: skip transmitted shadow ray if accounted for in photon map */
/* No longer needed?
if (shadowRayInPmap(r) || ambRayInPmap(r))
return(1); */
/* easy shadow test */
if (r->crtype & SHADOW && m->otype != MAT_TRANS)
return(1);
if (m->oargs.nfargs != (m->otype == MAT_TRANS ? 7 : 5))
objerror(m, USER, "bad number of arguments");
/* check for back side */
if (r->rod < 0.0) {
if (!backvis) {
raytrans(r);
return(1);
}
raytexture(r, m->omod);
flipsurface(r); /* reorient if backvis */
} else
raytexture(r, m->omod);
nd.mp = m;
nd.rp = r;
/* get material color */
setcolor(nd.mcolor, m->oargs.farg[0],
m->oargs.farg[1],
m->oargs.farg[2]);
/* get roughness */
nd.specfl = 0;
nd.alpha2 = m->oargs.farg[4];
if ((nd.alpha2 *= nd.alpha2) <= FTINY)
nd.specfl |= SP_PURE;
if ( (hastexture = (DOT(r->pert,r->pert) > FTINY*FTINY)) ) {
nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
} else {
VCOPY(nd.pnorm, r->ron);
nd.pdot = r->rod;
}
if (r->ro != NULL && isflat(r->ro->otype))
nd.specfl |= SP_FLAT;
if (nd.pdot < .001)
nd.pdot = .001; /* non-zero for dirnorm() */
multcolor(nd.mcolor, r->pcol); /* modify material color */
nd.rspec = m->oargs.farg[3];
/* compute Fresnel approx. */
if (nd.specfl & SP_PURE && nd.rspec >= FRESTHRESH) {
fest = FRESNE(nd.pdot);
nd.rspec += fest*(1. - nd.rspec);
} else
fest = 0.;
/* compute transmission */
if (m->otype == MAT_TRANS) {
nd.trans = m->oargs.farg[5]*(1.0 - nd.rspec);
nd.tspec = nd.trans * m->oargs.farg[6];
nd.tdiff = nd.trans - nd.tspec;
if (nd.tspec > FTINY) {
nd.specfl |= SP_TRAN;
/* check threshold */
if (!(nd.specfl & SP_PURE) &&
specthresh >= nd.tspec-FTINY)
nd.specfl |= SP_TBLT;
if (!hastexture || r->crtype & (SHADOW|AMBIENT)) {
VCOPY(nd.prdir, r->rdir);
} else {
/* perturb */
VSUB(nd.prdir, r->rdir, r->pert);
if (DOT(nd.prdir, r->ron) < -FTINY)
normalize(nd.prdir); /* OK */
else
VCOPY(nd.prdir, r->rdir);
}
}
} else
nd.tdiff = nd.tspec = nd.trans = 0.0;
/* diffuse reflection */
nd.rdiff = 1.0 - nd.trans - nd.rspec;
/* transmitted ray */
if ((nd.specfl&(SP_TRAN|SP_PURE|SP_TBLT)) == (SP_TRAN|SP_PURE)) {
RAY lr;
copycolor(lr.rcoef, nd.mcolor); /* modified by color */
scalecolor(lr.rcoef, nd.tspec);
if (rayorigin(&lr, TRANS, r, lr.rcoef) == 0) {
VCOPY(lr.rdir, nd.prdir);
rayvalue(&lr);
multcolor(lr.rcol, lr.rcoef);
addcolor(r->rcol, lr.rcol);
if (nd.tspec >= 1.0-FTINY) {
/* completely transparent */
multcolor(lr.mcol, lr.rcoef);
copycolor(r->mcol, lr.mcol);
r->rmt = r->rot + lr.rmt;
r->rxt = r->rot + lr.rxt;
} else if (nd.tspec > nd.tdiff + nd.rdiff)
r->rxt = r->rot + raydistance(&lr);
}
}
if (r->crtype & SHADOW) /* the rest is shadow */
return(1);
/* get specular reflection */
if (nd.rspec > FTINY) {
nd.specfl |= SP_REFL;
/* compute specular color */
if (m->otype != MAT_METAL) {
setcolor(nd.scolor, nd.rspec, nd.rspec, nd.rspec);
} else if (fest > FTINY) {
d = m->oargs.farg[3]*(1. - fest);
for (i = 0; i < 3; i++)
colval(nd.scolor,i) = fest +
colval(nd.mcolor,i)*d;
} else {
copycolor(nd.scolor, nd.mcolor);
scalecolor(nd.scolor, nd.rspec);
}
/* check threshold */
if (!(nd.specfl & SP_PURE) && specthresh >= nd.rspec-FTINY)
nd.specfl |= SP_RBLT;
/* compute reflected ray */
VSUM(nd.vrefl, r->rdir, nd.pnorm, 2.*nd.pdot);
/* penetration? */
if (hastexture && DOT(nd.vrefl, r->ron) <= FTINY)
VSUM(nd.vrefl, r->rdir, r->ron, 2.*r->rod);
checknorm(nd.vrefl);
}
/* reflected ray */
if ((nd.specfl&(SP_REFL|SP_PURE|SP_RBLT)) == (SP_REFL|SP_PURE)) {
RAY lr;
if (rayorigin(&lr, REFLECTED, r, nd.scolor) == 0) {
VCOPY(lr.rdir, nd.vrefl);
rayvalue(&lr);
multcolor(lr.rcol, lr.rcoef);
copycolor(r->mcol, lr.rcol);
addcolor(r->rcol, lr.rcol);
r->rmt = r->rot;
if (nd.specfl & SP_FLAT &&
!hastexture | (r->crtype & AMBIENT))
r->rmt += raydistance(&lr);
}
}
if (nd.specfl & SP_PURE && nd.rdiff <= FTINY && nd.tdiff <= FTINY)
return(1); /* 100% pure specular */
if (!(nd.specfl & SP_PURE))
gaussamp(&nd); /* checks *BLT flags */
if (nd.rdiff > FTINY) { /* ambient from this side */
copycolor(ctmp, nd.mcolor); /* modified by material color */
scalecolor(ctmp, nd.rdiff);
if (nd.specfl & SP_RBLT) /* add in specular as well? */
addcolor(ctmp, nd.scolor);
multambient(ctmp, r, hastexture ? nd.pnorm : r->ron);
addcolor(r->rcol, ctmp); /* add to returned color */
}
if (nd.tdiff > FTINY) { /* ambient from other side */
copycolor(ctmp, nd.mcolor); /* modified by color */
if (nd.specfl & SP_TBLT)
scalecolor(ctmp, nd.trans);
else
scalecolor(ctmp, nd.tdiff);
flipsurface(r);
if (hastexture) {
FVECT bnorm;
bnorm[0] = -nd.pnorm[0];
bnorm[1] = -nd.pnorm[1];
bnorm[2] = -nd.pnorm[2];
multambient(ctmp, r, bnorm);
} else
multambient(ctmp, r, r->ron);
addcolor(r->rcol, ctmp);
flipsurface(r);
}
/* add direct component */
direct(r, dirnorm, &nd);
return(1);
}
static void
gaussamp( /* sample Gaussian specular */
NORMDAT *np
)
{
RAY sr;
FVECT u, v, h;
double rv[2];
double d, sinp, cosp;
COLOR scol;
int maxiter, ntrials, nstarget, nstaken;
int i;
/* quick test */
if ((np->specfl & (SP_REFL|SP_RBLT)) != SP_REFL &&
(np->specfl & (SP_TRAN|SP_TBLT)) != SP_TRAN)
return;
/* set up sample coordinates */
getperpendicular(u, np->pnorm, rand_samp);
fcross(v, np->pnorm, u);
/* compute reflection */
if ((np->specfl & (SP_REFL|SP_RBLT)) == SP_REFL &&
rayorigin(&sr, SPECULAR, np->rp, np->scolor) == 0) {
nstarget = 1;
if (specjitter > 1.5) { /* multiple samples? */
nstarget = specjitter*np->rp->rweight + .5;
if (sr.rweight <= minweight*nstarget)
nstarget = sr.rweight/minweight;
if (nstarget > 1) {
d = 1./nstarget;
scalecolor(sr.rcoef, d);
sr.rweight *= d;
} else
nstarget = 1;
}
setcolor(scol, 0., 0., 0.);
dimlist[ndims++] = (int)(size_t)np->mp;
maxiter = MAXITER*nstarget;
for (nstaken = ntrials = 0; nstaken < nstarget &&
ntrials < maxiter; ntrials++) {
if (ntrials)
d = frandom();
else
d = urand(ilhash(dimlist,ndims)+samplendx);
multisamp(rv, 2, d);
d = 2.0*PI * rv[0];
cosp = tcos(d);
sinp = tsin(d);
if ((0. <= specjitter) & (specjitter < 1.))
rv[1] = 1.0 - specjitter*rv[1];
if (rv[1] <= FTINY)
d = 1.0;
else
d = sqrt( np->alpha2 * -log(rv[1]) );
for (i = 0; i < 3; i++)
h[i] = np->pnorm[i] + d*(cosp*u[i] + sinp*v[i]);
d = -2.0 * DOT(h, np->rp->rdir) / (1.0 + d*d);
VSUM(sr.rdir, np->rp->rdir, h, d);
/* sample rejection test */
if ((d = DOT(sr.rdir, np->rp->ron)) <= FTINY)
continue;
checknorm(sr.rdir);
if (nstarget > 1) { /* W-G-M-D adjustment */
if (nstaken) rayclear(&sr);
rayvalue(&sr);
d = 2./(1. + np->rp->rod/d);
scalecolor(sr.rcol, d);
addcolor(scol, sr.rcol);
} else {
rayvalue(&sr);
multcolor(sr.rcol, sr.rcoef);
addcolor(np->rp->rcol, sr.rcol);
}
++nstaken;
}
if (nstarget > 1) { /* final W-G-M-D weighting */
multcolor(scol, sr.rcoef);
d = (double)nstarget/ntrials;
scalecolor(scol, d);
addcolor(np->rp->rcol, scol);
}
ndims--;
}
/* compute transmission */
copycolor(sr.rcoef, np->mcolor); /* modified by color */
scalecolor(sr.rcoef, np->tspec);
if ((np->specfl & (SP_TRAN|SP_TBLT)) == SP_TRAN &&
rayorigin(&sr, SPECULAR, np->rp, sr.rcoef) == 0) {
nstarget = 1;
if (specjitter > 1.5) { /* multiple samples? */
nstarget = specjitter*np->rp->rweight + .5;
if (sr.rweight <= minweight*nstarget)
nstarget = sr.rweight/minweight;
if (nstarget > 1) {
d = 1./nstarget;
scalecolor(sr.rcoef, d);
sr.rweight *= d;
} else
nstarget = 1;
}
dimlist[ndims++] = (int)(size_t)np->mp;
maxiter = MAXITER*nstarget;
for (nstaken = ntrials = 0; nstaken < nstarget &&
ntrials < maxiter; ntrials++) {
if (ntrials)
d = frandom();
else
d = urand(ilhash(dimlist,ndims)+samplendx);
multisamp(rv, 2, d);
d = 2.0*PI * rv[0];
cosp = tcos(d);
sinp = tsin(d);
if ((0. <= specjitter) & (specjitter < 1.))
rv[1] = 1.0 - specjitter*rv[1];
if (rv[1] <= FTINY)
d = 1.0;
else
d = sqrt( np->alpha2 * -log(rv[1]) );
for (i = 0; i < 3; i++)
sr.rdir[i] = np->prdir[i] + d*(cosp*u[i] + sinp*v[i]);
/* sample rejection test */
if (DOT(sr.rdir, np->rp->ron) >= -FTINY)
continue;
normalize(sr.rdir); /* OK, normalize */
if (nstaken) /* multi-sampling */
rayclear(&sr);
rayvalue(&sr);
multcolor(sr.rcol, sr.rcoef);
addcolor(np->rp->rcol, sr.rcol);
++nstaken;
}
ndims--;
}
}

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