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Wed, May 22, 02:33

aniso.c
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#ifndef lint
static const char RCSid[] = "$Id: aniso.c,v 2.61 2015/09/02 18:59:01 greg Exp $";
#endif
/*
* Shading functions for anisotropic materials.
*/
#include "copyright.h"
#include "ray.h"
#include "ambient.h"
#include "otypes.h"
#include "rtotypes.h"
#include "source.h"
#include "func.h"
#include "random.h"
#include "pmapmat.h"
#ifndef MAXITER
#define MAXITER 10 /* maximum # specular ray attempts */
#endif
/*
* This routine implements the anisotropic Gaussian
* model described by Ward in Siggraph `92 article, updated with
* normalization and sampling adjustments due to Geisler-Moroder and Duer.
* We orient the surface towards the incoming ray, so a single
* surface can be used to represent an infinitely thin object.
*
* Arguments for MAT_PLASTIC2 and MAT_METAL2 are:
* 4+ ux uy uz funcfile [transform...]
* 0
* 6 red grn blu specular-frac. u-rough v-rough
*
* Real arguments for MAT_TRANS2 are:
* 8 red grn blu rspec u-rough v-rough trans tspec
*/
/* specularity flags */
#define SP_REFL 01 /* has reflected specular component */
#define SP_TRAN 02 /* has transmitted specular */
#define SP_FLAT 04 /* reflecting surface is flat */
#define SP_RBLT 010 /* reflection below sample threshold */
#define SP_TBLT 020 /* 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 reflected direction */
FVECT prdir; /* vector in transmitted direction */
FVECT u, v; /* u and v vectors orienting anisotropy */
double u_alpha; /* u roughness */
double v_alpha; /* v roughness */
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 */
} ANISODAT; /* anisotropic material data */
static void getacoords(ANISODAT *np);
static void agaussamp(ANISODAT *np);
static void
diraniso( /* compute source contribution */
COLOR cval, /* returned coefficient */
void *nnp, /* material data */
FVECT ldir, /* light source direction */
double omega /* light source size */
)
{
ANISODAT *np = nnp;
double ldot;
double dtmp, dtmp1, dtmp2;
FVECT h;
double au2, av2;
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 */
if ((ldot > FTINY) & (np->rdiff > 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 * np->rdiff * (1.0/PI);
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
if ((ldot < -FTINY) & (np->tdiff > FTINY)) {
/*
* Compute diffuse transmission.
*/
copycolor(ctmp, np->mcolor);
dtmp = -ldot * omega * np->tdiff * (1.0/PI);
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
if (ambRayInPmap(np->rp))
return; /* specular accounted for in photon map */
if (ldot > FTINY && np->specfl&SP_REFL) {
/*
* Compute specular reflection coefficient using
* anisotropic Gaussian distribution model.
*/
/* add source width if flat */
if (np->specfl & SP_FLAT)
au2 = av2 = omega * (0.25/PI);
else
au2 = av2 = 0.0;
au2 += np->u_alpha*np->u_alpha;
av2 += np->v_alpha*np->v_alpha;
/* half vector */
VSUB(h, ldir, np->rp->rdir);
/* ellipse */
dtmp1 = DOT(np->u, h);
dtmp1 *= dtmp1 / au2;
dtmp2 = DOT(np->v, h);
dtmp2 *= dtmp2 / av2;
/* new W-G-M-D model */
dtmp = DOT(np->pnorm, h);
dtmp *= dtmp;
dtmp1 = (dtmp1 + dtmp2) / dtmp;
dtmp = exp(-dtmp1) * DOT(h,h) /
(PI * dtmp*dtmp * sqrt(au2*av2));
/* 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) {
/*
* Compute specular transmission. Specular transmission
* is always modified by material color.
*/
/* roughness + source */
au2 = av2 = omega * (1.0/PI);
au2 += np->u_alpha*np->u_alpha;
av2 += np->v_alpha*np->v_alpha;
/* "half vector" */
VSUB(h, ldir, np->prdir);
dtmp = DOT(h,h);
if (dtmp > FTINY*FTINY) {
dtmp1 = DOT(h,np->pnorm);
dtmp = 1.0 - dtmp1*dtmp1/dtmp;
if (dtmp > FTINY*FTINY) {
dtmp1 = DOT(h,np->u);
dtmp1 *= dtmp1 / au2;
dtmp2 = DOT(h,np->v);
dtmp2 *= dtmp2 / av2;
dtmp = (dtmp1 + dtmp2) / dtmp;
}
} else
dtmp = 0.0;
/* Gaussian */
dtmp = exp(-dtmp) * (1.0/PI) * sqrt(-ldot/(np->pdot*au2*av2));
/* worth using? */
if (dtmp > FTINY) {
copycolor(ctmp, np->mcolor);
dtmp *= np->tspec * omega;
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
}
}
int
m_aniso( /* shade ray that hit something anisotropic */
OBJREC *m,
RAY *r
)
{
ANISODAT nd;
COLOR ctmp;
int i;
/* easy shadow test */
if (r->crtype & SHADOW)
return(1);
if (m->oargs.nfargs != (m->otype == MAT_TRANS2 ? 8 : 6))
objerror(m, USER, "bad number of real 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);
/* get material color */
nd.mp = m;
nd.rp = r;
setcolor(nd.mcolor, m->oargs.farg[0],
m->oargs.farg[1],
m->oargs.farg[2]);
/* get roughness */
nd.specfl = 0;
nd.u_alpha = m->oargs.farg[4];
nd.v_alpha = m->oargs.farg[5];
if ((nd.u_alpha <= FTINY) | (nd.v_alpha <= FTINY))
objerror(m, USER, "roughness too small");
nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
if (nd.pdot < .001)
nd.pdot = .001; /* non-zero for diraniso() */
multcolor(nd.mcolor, r->pcol); /* modify material color */
/* get specular component */
if ((nd.rspec = m->oargs.farg[3]) > FTINY) {
nd.specfl |= SP_REFL;
/* compute specular color */
if (m->otype == MAT_METAL2)
copycolor(nd.scolor, nd.mcolor);
else
setcolor(nd.scolor, 1.0, 1.0, 1.0);
scalecolor(nd.scolor, nd.rspec);
/* check threshold */
if (specthresh >= nd.rspec-FTINY)
nd.specfl |= SP_RBLT;
/* compute refl. direction */
VSUM(nd.vrefl, r->rdir, nd.pnorm, 2.0*nd.pdot);
if (DOT(nd.vrefl, r->ron) <= FTINY) /* penetration? */
VSUM(nd.vrefl, r->rdir, r->ron, 2.0*r->rod);
}
/* compute transmission */
if (m->otype == MAT_TRANS2) {
nd.trans = m->oargs.farg[6]*(1.0 - nd.rspec);
nd.tspec = nd.trans * m->oargs.farg[7];
nd.tdiff = nd.trans - nd.tspec;
if (nd.tspec > FTINY) {
nd.specfl |= SP_TRAN;
/* check threshold */
if (specthresh >= nd.tspec-FTINY)
nd.specfl |= SP_TBLT;
if (DOT(r->pert,r->pert) <= FTINY*FTINY) {
VCOPY(nd.prdir, r->rdir);
} else {
for (i = 0; i < 3; i++) /* perturb */
nd.prdir[i] = r->rdir[i] - r->pert[i];
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;
if (r->ro != NULL && isflat(r->ro->otype))
nd.specfl |= SP_FLAT;
getacoords(&nd); /* set up coordinates */
if (nd.specfl & (SP_REFL|SP_TRAN))
agaussamp(&nd);
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, nd.pnorm);
addcolor(r->rcol, ctmp); /* add to returned color */
}
if (nd.tdiff > FTINY) { /* ambient from other side */
FVECT bnorm;
flipsurface(r);
bnorm[0] = -nd.pnorm[0];
bnorm[1] = -nd.pnorm[1];
bnorm[2] = -nd.pnorm[2];
copycolor(ctmp, nd.mcolor); /* modified by color */
if (nd.specfl & SP_TBLT)
scalecolor(ctmp, nd.trans);
else
scalecolor(ctmp, nd.tdiff);
multambient(ctmp, r, bnorm);
addcolor(r->rcol, ctmp);
flipsurface(r);
}
/* add direct component */
direct(r, diraniso, &nd);
return(1);
}
static void
getacoords( /* set up coordinate system */
ANISODAT *np
)
{
MFUNC *mf;
int i;
mf = getfunc(np->mp, 3, 0x7, 1);
setfunc(np->mp, np->rp);
errno = 0;
for (i = 0; i < 3; i++)
np->u[i] = evalue(mf->ep[i]);
if ((errno == EDOM) | (errno == ERANGE))
np->u[0] = np->u[1] = np->u[2] = 0.0;
if (mf->fxp != &unitxf)
multv3(np->u, np->u, mf->fxp->xfm);
fcross(np->v, np->pnorm, np->u);
if (normalize(np->v) == 0.0) {
if (fabs(np->u_alpha - np->v_alpha) > 0.001)
objerror(np->mp, WARNING, "illegal orientation vector");
getperpendicular(np->u, np->pnorm, 1); /* punting */
fcross(np->v, np->pnorm, np->u);
np->u_alpha = np->v_alpha = sqrt( 0.5 *
(np->u_alpha*np->u_alpha + np->v_alpha*np->v_alpha) );
} else
fcross(np->u, np->v, np->pnorm);
}
static void
agaussamp( /* sample anisotropic Gaussian specular */
ANISODAT *np
)
{
RAY sr;
FVECT h;
double rv[2];
double d, sinp, cosp;
COLOR scol;
int maxiter, ntrials, nstarget, nstaken;
int i;
/* 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) * np->u_alpha;
sinp = tsin(d) * np->v_alpha;
d = 1./sqrt(cosp*cosp + sinp*sinp);
cosp *= d;
sinp *= d;
if ((0. <= specjitter) & (specjitter < 1.))
rv[1] = 1.0 - specjitter*rv[1];
if (rv[1] <= FTINY)
d = 1.0;
else
d = sqrt(-log(rv[1]) /
(cosp*cosp/(np->u_alpha*np->u_alpha) +
sinp*sinp/(np->v_alpha*np->v_alpha)));
for (i = 0; i < 3; i++)
h[i] = np->pnorm[i] +
d*(cosp*np->u[i] + sinp*np->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); /* modify by material 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)+1823+samplendx);
multisamp(rv, 2, d);
d = 2.0*PI * rv[0];
cosp = tcos(d) * np->u_alpha;
sinp = tsin(d) * np->v_alpha;
d = 1./sqrt(cosp*cosp + sinp*sinp);
cosp *= d;
sinp *= d;
if ((0. <= specjitter) & (specjitter < 1.))
rv[1] = 1.0 - specjitter*rv[1];
if (rv[1] <= FTINY)
d = 1.0;
else
d = sqrt(-log(rv[1]) /
(cosp*cosp/(np->u_alpha*np->u_alpha) +
sinp*sinp/(np->v_alpha*np->v_alpha)));
for (i = 0; i < 3; i++)
sr.rdir[i] = np->prdir[i] +
d*(cosp*np->u[i] + sinp*np->v[i]);
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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