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Mon, May 6, 15:40

ashikhmin.c
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#ifndef lint
static const char RCSid[] = "$Id: ashikhmin.c,v 2.6 2015/09/02 18:59:01 greg Exp $";
#endif
/*
* Shading functions for Ashikhmin-Shirley 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
/*
* Ashikhmin-Shirley model
*
* Arguments for MAT_ASHIKHMIN are:
* 4+ ux uy uz funcfile [transform...]
* 0
* 8 dred dgrn dblu sred sgrn sblu u-power v-power
*/
/* specularity flags */
#define SPA_REFL 01 /* has reflected specular component */
#define SPA_FLAT 02 /* reflecting surface is flat */
#define SPA_RBLT 010 /* reflection below sample 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 u, v; /* u and v vectors orienting anisotropy */
double u_power; /* u power */
double v_power; /* v power */
FVECT pnorm; /* perturbed surface normal */
double pdot; /* perturbed dot product */
} ASHIKDAT; /* anisotropic material data */
static void getacoords_as(ASHIKDAT *np);
static void ashiksamp(ASHIKDAT *np);
#undef MAX
#define MAX(a,b) ((a)>(b) ? (a) : (b))
static double
schlick_fres(double dprod)
{
double pf = 1. - dprod;
return(pf*pf*pf*pf*pf);
}
static void
dirashik( /* compute source contribution */
COLOR cval, /* returned coefficient */
void *nnp, /* material data */
FVECT ldir, /* light source direction */
double omega /* light source size */
)
{
ASHIKDAT *np = nnp;
double ldot;
double dtmp, dtmp1, dtmp2;
FVECT h;
COLOR ctmp;
setcolor(cval, 0.0, 0.0, 0.0);
ldot = DOT(np->pnorm, ldir);
if (ldot < 0.0)
return; /* wrong side */
/*
* Compute and add diffuse reflected component to returned
* color.
*/
copycolor(ctmp, np->mcolor);
dtmp = ldot * omega * (1.0/PI) * (1. - schlick_fres(ldot));
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
if (!(np->specfl & SPA_REFL) || ambRayInPmap(np->rp))
return;
/*
* Compute specular reflection coefficient
*/
/* half vector */
VSUB(h, ldir, np->rp->rdir);
normalize(h);
/* ellipse */
dtmp1 = DOT(np->u, h);
dtmp1 *= dtmp1 * np->u_power;
dtmp2 = DOT(np->v, h);
dtmp2 *= dtmp2 * np->v_power;
/* Ashikhmin-Shirley model*/
dtmp = DOT(np->pnorm, h);
dtmp = pow(dtmp, (dtmp1+dtmp2)/(1.-dtmp*dtmp));
dtmp *= sqrt((np->u_power+1.)*(np->v_power+1.));
dtmp /= 8.*PI * DOT(ldir,h) * MAX(ldot,np->pdot);
/* worth using? */
if (dtmp > FTINY) {
copycolor(ctmp, np->scolor);
dtmp *= ldot * omega;
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
}
int
m_ashikhmin( /* shade ray that hit something anisotropic */
OBJREC *m,
RAY *r
)
{
ASHIKDAT nd;
COLOR ctmp;
double fres;
int i;
/* easy shadow test */
if (r->crtype & SHADOW)
return(1);
if (m->oargs.nfargs != 8)
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]);
setcolor(nd.scolor, m->oargs.farg[3],
m->oargs.farg[4],
m->oargs.farg[5]);
/* get specular power */
nd.specfl = 0;
nd.u_power = m->oargs.farg[6];
nd.v_power = m->oargs.farg[7];
nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
if (nd.pdot < .001)
nd.pdot = .001; /* non-zero for dirashik() */
multcolor(nd.mcolor, r->pcol); /* modify diffuse color */
if (bright(nd.scolor) > FTINY) { /* adjust specular color */
nd.specfl |= SPA_REFL;
/* check threshold */
if (specthresh >= bright(nd.scolor)-FTINY)
nd.specfl |= SPA_RBLT;
fres = schlick_fres(nd.pdot); /* Schick's Fresnel approx */
for (i = 0; i < 3; i++)
colval(nd.scolor,i) += (1.-colval(nd.scolor,i))*fres;
}
if (r->ro != NULL && isflat(r->ro->otype))
nd.specfl |= SPA_FLAT;
/* set up coordinates */
getacoords_as(&nd);
/* specular sampling? */
if ((nd.specfl & (SPA_REFL|SPA_RBLT)) == SPA_REFL)
ashiksamp(&nd);
/* diffuse interreflection */
if (bright(nd.mcolor) > FTINY) {
copycolor(ctmp, nd.mcolor); /* modified by material color */
if (nd.specfl & SPA_RBLT) /* add in specular as well? */
addcolor(ctmp, nd.scolor);
multambient(ctmp, r, nd.pnorm);
addcolor(r->rcol, ctmp); /* add to returned color */
}
direct(r, dirashik, &nd); /* add direct component */
return(1);
}
static void
getacoords_as( /* set up coordinate system */
ASHIKDAT *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_power - np->v_power) > 0.1)
objerror(np->mp, WARNING, "bad orientation vector");
getperpendicular(np->u, np->pnorm, 1); /* punting */
fcross(np->v, np->pnorm, np->u);
np->u_power = np->v_power =
2./(1./(np->u_power+1e-5) + 1./(np->v_power+1e-5));
} else
fcross(np->u, np->v, np->pnorm);
}
static void
ashiksamp( /* sample anisotropic Ashikhmin-Shirley specular */
ASHIKDAT *np
)
{
RAY sr;
FVECT h;
double rv[2], dtmp;
double cosph, sinph, costh, sinth;
int maxiter, ntrials, nstarget, nstaken;
int i;
if (rayorigin(&sr, SPECULAR, np->rp, np->scolor) < 0)
return;
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) {
dtmp = 1./nstarget;
scalecolor(sr.rcoef, dtmp);
sr.rweight *= dtmp;
} else
nstarget = 1;
}
dimlist[ndims++] = (int)(size_t)np->mp;
maxiter = MAXITER*nstarget;
for (nstaken = ntrials = 0; nstaken < nstarget &&
ntrials < maxiter; ntrials++) {
if (ntrials)
dtmp = frandom();
else
dtmp = urand(ilhash(dimlist,ndims)+647+samplendx);
multisamp(rv, 2, dtmp);
dtmp = 2.*PI * rv[0];
cosph = sqrt(np->v_power + 1.) * tcos(dtmp);
sinph = sqrt(np->u_power + 1.) * tsin(dtmp);
dtmp = 1./sqrt(cosph*cosph + sinph*sinph);
cosph *= dtmp;
sinph *= dtmp;
costh = pow(rv[1], 1./(np->u_power*cosph*cosph+np->v_power*sinph*sinph+1.));
if (costh <= FTINY)
continue;
sinth = sqrt(1. - costh*costh);
for (i = 0; i < 3; i++)
h[i] = cosph*sinth*np->u[i] + sinph*sinth*np->v[i] + costh*np->pnorm[i];
if (nstaken)
rayclear(&sr);
dtmp = -2.*DOT(h, np->rp->rdir);
VSUM(sr.rdir, np->rp->rdir, h, dtmp);
/* sample rejection test */
if (DOT(sr.rdir, np->rp->ron) <= FTINY)
continue;
checknorm(sr.rdir);
rayvalue(&sr);
multcolor(sr.rcol, sr.rcoef);
addcolor(np->rp->rcol, sr.rcol);
++nstaken;
}
ndims--;
}

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