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m_brdf.c
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Fri, Nov 8, 15:10

m_brdf.c
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#ifndef lint
static const char RCSid[] = "$Id: m_brdf.c,v 2.39 2019/04/19 19:01:32 greg Exp $";
#endif
/*
* Shading for materials with arbitrary BRDF's
*/
#include "copyright.h"
#include "ray.h"
#include "ambient.h"
#include "data.h"
#include "source.h"
#include "otypes.h"
#include "rtotypes.h"
#include "func.h"
#include "pmapmat.h"
/*
* Arguments to this material include the color and specularity.
* String arguments include the reflection function and files.
* The BRDF is currently used just for the specular component to light
* sources. Reflectance values or data coordinates are functions
* of the direction to the light source. (Data modification functions
* are passed the source direction as args 2-4.)
* We orient the surface towards the incoming ray, so a single
* surface can be used to represent an infinitely thin object.
*
* Arguments for MAT_PFUNC and MAT_MFUNC are:
* 2+ func funcfile transform
* 0
* 4+ red grn blu specularity A5 ..
*
* Arguments for MAT_PDATA and MAT_MDATA are:
* 4+ func datafile funcfile v0 .. transform
* 0
* 4+ red grn blu specularity A5 ..
*
* Arguments for MAT_TFUNC are:
* 2+ func funcfile transform
* 0
* 6+ red grn blu rspec trans tspec A7 ..
*
* Arguments for MAT_TDATA are:
* 4+ func datafile funcfile v0 .. transform
* 0
* 6+ red grn blu rspec trans tspec A7 ..
*
* Arguments for the more general MAT_BRTDF are:
* 10+ rrefl grefl brefl
* rtrns gtrns btrns
* rbrtd gbrtd bbrtd
* funcfile transform
* 0
* 9+ rdf gdf bdf
* rdb gdb bdb
* rdt gdt bdt A10 ..
*
* In addition to the normal variables available to functions,
* we define the following:
* NxP, NyP, NzP - perturbed surface normal
* RdotP - perturbed ray dot product
* CrP, CgP, CbP - perturbed material color (or pattern)
*/
typedef struct {
OBJREC *mp; /* material pointer */
RAY *pr; /* intersected ray */
DATARRAY *dp; /* data array for PDATA, MDATA or TDATA */
COLOR mcolor; /* material (or pattern) color */
COLOR rdiff; /* diffuse reflection */
COLOR tdiff; /* diffuse transmission */
double rspec; /* specular reflectance (1 for BRDTF) */
double trans; /* transmissivity (.5 for BRDTF) */
double tspec; /* specular transmittance (1 for BRDTF) */
FVECT pnorm; /* perturbed surface normal */
double pdot; /* perturbed dot product */
} BRDFDAT; /* BRDF material data */
static int setbrdfunc(BRDFDAT *np);
static void
dirbrdf( /* compute source contribution */
COLOR cval, /* returned coefficient */
void *nnp, /* material data */
FVECT ldir, /* light source direction */
double omega /* light source size */
)
{
BRDFDAT *np = nnp;
double ldot;
double dtmp;
COLOR ctmp;
FVECT ldx;
static double vldx[5], pt[MAXDIM];
char **sa;
int i;
#define lddx (vldx+1)
setcolor(cval, 0.0, 0.0, 0.0);
ldot = DOT(np->pnorm, ldir);
if (ldot <= FTINY && ldot >= -FTINY)
return; /* too close to grazing */
if (ldot < 0.0 ? np->trans <= FTINY : np->trans >= 1.0-FTINY)
return; /* wrong side */
if (ldot > 0.0) {
/*
* 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->rdiff);
dtmp = ldot * omega / PI;
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
} else {
/*
* Diffuse transmitted component.
*/
copycolor(ctmp, np->tdiff);
dtmp = -ldot * omega / PI;
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
if ((ldot > 0.0 ? np->rspec <= FTINY : np->tspec <= FTINY) ||
ambRayInPmap(np->pr))
return; /* diffuse only */
/* set up function */
setbrdfunc(np);
sa = np->mp->oargs.sarg;
errno = 0;
/* transform light vector */
multv3(ldx, ldir, funcxf.xfm);
for (i = 0; i < 3; i++)
lddx[i] = ldx[i]/funcxf.sca;
lddx[3] = omega;
/* compute BRTDF */
if (np->mp->otype == MAT_BRTDF) {
if (sa[6][0] == '0' && !sa[6][1]) /* special case */
colval(ctmp,RED) = 0.0;
else
colval(ctmp,RED) = funvalue(sa[6], 4, lddx);
if (sa[7][0] == '0' && !sa[7][1])
colval(ctmp,GRN) = 0.0;
else if (!strcmp(sa[7],sa[6]))
colval(ctmp,GRN) = colval(ctmp,RED);
else
colval(ctmp,GRN) = funvalue(sa[7], 4, lddx);
if (sa[8][0] == '0' && !sa[8][1])
colval(ctmp,BLU) = 0.0;
else if (!strcmp(sa[8],sa[6]))
colval(ctmp,BLU) = colval(ctmp,RED);
else if (!strcmp(sa[8],sa[7]))
colval(ctmp,BLU) = colval(ctmp,GRN);
else
colval(ctmp,BLU) = funvalue(sa[8], 4, lddx);
dtmp = bright(ctmp);
} else if (np->dp == NULL) {
dtmp = funvalue(sa[0], 4, lddx);
setcolor(ctmp, dtmp, dtmp, dtmp);
} else {
for (i = 0; i < np->dp->nd; i++)
pt[i] = funvalue(sa[3+i], 4, lddx);
vldx[0] = datavalue(np->dp, pt);
dtmp = funvalue(sa[0], 5, vldx);
setcolor(ctmp, dtmp, dtmp, dtmp);
}
if ((errno == EDOM) | (errno == ERANGE)) {
objerror(np->mp, WARNING, "compute error");
return;
}
if (dtmp <= FTINY)
return;
if (ldot > 0.0) {
/*
* Compute reflected non-diffuse component.
*/
if ((np->mp->otype == MAT_MFUNC) | (np->mp->otype == MAT_MDATA))
multcolor(ctmp, np->mcolor);
dtmp = ldot * omega * np->rspec;
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
} else {
/*
* Compute transmitted non-diffuse component.
*/
if ((np->mp->otype == MAT_TFUNC) | (np->mp->otype == MAT_TDATA))
multcolor(ctmp, np->mcolor);
dtmp = -ldot * omega * np->tspec;
scalecolor(ctmp, dtmp);
addcolor(cval, ctmp);
}
#undef lddx
}
int
m_brdf( /* color a ray that hit a BRDTfunc material */
OBJREC *m,
RAY *r
)
{
int hitfront = 1;
BRDFDAT nd;
RAY sr;
int hasrefl, hastrans;
int hastexture;
COLOR ctmp;
FVECT vtmp;
double d;
MFUNC *mf;
int i;
/* check arguments */
if ((m->oargs.nsargs < 10) | (m->oargs.nfargs < 9))
objerror(m, USER, "bad # arguments");
nd.mp = m;
nd.pr = r;
/* dummy values */
nd.rspec = nd.tspec = 1.0;
nd.trans = 0.5;
/* diffuse reflectance */
if (r->rod > 0.0)
setcolor(nd.rdiff, m->oargs.farg[0],
m->oargs.farg[1],
m->oargs.farg[2]);
else
setcolor(nd.rdiff, m->oargs.farg[3],
m->oargs.farg[4],
m->oargs.farg[5]);
/* diffuse transmittance */
setcolor(nd.tdiff, m->oargs.farg[6],
m->oargs.farg[7],
m->oargs.farg[8]);
/* get modifiers */
raytexture(r, m->omod);
hastexture = (DOT(r->pert,r->pert) > FTINY*FTINY);
if (hastexture) { /* perturb normal */
nd.pdot = raynormal(nd.pnorm, r);
} else {
VCOPY(nd.pnorm, r->ron);
nd.pdot = r->rod;
}
if (r->rod < 0.0) { /* orient perturbed values */
nd.pdot = -nd.pdot;
for (i = 0; i < 3; i++) {
nd.pnorm[i] = -nd.pnorm[i];
r->pert[i] = -r->pert[i];
}
hitfront = 0;
}
copycolor(nd.mcolor, r->pcol); /* get pattern color */
multcolor(nd.rdiff, nd.mcolor); /* modify diffuse values */
multcolor(nd.tdiff, nd.mcolor);
hasrefl = (bright(nd.rdiff) > FTINY);
hastrans = (bright(nd.tdiff) > FTINY);
/* load cal file */
nd.dp = NULL;
mf = getfunc(m, 9, 0x3f, 0);
/* compute transmitted ray */
setbrdfunc(&nd);
errno = 0;
setcolor(ctmp, evalue(mf->ep[3]),
evalue(mf->ep[4]),
evalue(mf->ep[5]));
if ((errno == EDOM) | (errno == ERANGE))
objerror(m, WARNING, "compute error");
else if (rayorigin(&sr, TRANS, r, ctmp) == 0) {
if (hastexture && !(r->crtype & (SHADOW|AMBIENT))) {
/* perturb direction */
VSUB(sr.rdir, r->rdir, r->pert);
if (normalize(sr.rdir) == 0.0) {
objerror(m, WARNING, "illegal perturbation");
VCOPY(sr.rdir, r->rdir);
}
} else {
VCOPY(sr.rdir, r->rdir);
}
rayvalue(&sr);
multcolor(sr.rcol, sr.rcoef);
addcolor(r->rcol, sr.rcol);
if ((!hastexture || r->crtype & (SHADOW|AMBIENT)) &&
nd.tspec > bright(nd.tdiff) + bright(nd.rdiff))
r->rxt = r->rot + raydistance(&sr);
}
if (r->crtype & SHADOW) /* the rest is shadow */
return(1);
/* compute reflected ray */
setbrdfunc(&nd);
errno = 0;
setcolor(ctmp, evalue(mf->ep[0]),
evalue(mf->ep[1]),
evalue(mf->ep[2]));
if ((errno == EDOM) | (errno == ERANGE))
objerror(m, WARNING, "compute error");
else if (rayorigin(&sr, REFLECTED, r, ctmp) == 0) {
VSUM(sr.rdir, r->rdir, nd.pnorm, 2.*nd.pdot);
checknorm(sr.rdir);
rayvalue(&sr);
multcolor(sr.rcol, sr.rcoef);
copycolor(r->mcol, sr.rcol);
addcolor(r->rcol, sr.rcol);
r->rmt = r->rot;
if (r->ro != NULL && isflat(r->ro->otype) &&
!hastexture | (r->crtype & AMBIENT))
r->rmt += raydistance(&sr);
}
/* compute ambient */
if (hasrefl) {
if (!hitfront)
flipsurface(r);
copycolor(ctmp, nd.rdiff);
multambient(ctmp, r, nd.pnorm);
addcolor(r->rcol, ctmp); /* add to returned color */
if (!hitfront)
flipsurface(r);
}
if (hastrans) { /* from other side */
if (hitfront)
flipsurface(r);
vtmp[0] = -nd.pnorm[0];
vtmp[1] = -nd.pnorm[1];
vtmp[2] = -nd.pnorm[2];
copycolor(ctmp, nd.tdiff);
multambient(ctmp, r, vtmp);
addcolor(r->rcol, ctmp);
if (hitfront)
flipsurface(r);
}
if (hasrefl | hastrans || m->oargs.sarg[6][0] != '0')
direct(r, dirbrdf, &nd); /* add direct component */
return(1);
}
int
m_brdf2( /* color a ray that hit a BRDF material */
OBJREC *m,
RAY *r
)
{
BRDFDAT nd;
COLOR ctmp;
FVECT vtmp;
double dtmp;
/* always a shadow */
if (r->crtype & SHADOW)
return(1);
/* check arguments */
if ((m->oargs.nsargs < (hasdata(m->otype)?4:2)) | (m->oargs.nfargs <
((m->otype==MAT_TFUNC)|(m->otype==MAT_TDATA)?6:4)))
objerror(m, USER, "bad # 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.pr = r;
/* get material color */
setcolor(nd.mcolor, m->oargs.farg[0],
m->oargs.farg[1],
m->oargs.farg[2]);
/* get specular component */
nd.rspec = m->oargs.farg[3];
/* compute transmittance */
if ((m->otype == MAT_TFUNC) | (m->otype == MAT_TDATA)) {
nd.trans = m->oargs.farg[4]*(1.0 - nd.rspec);
nd.tspec = nd.trans * m->oargs.farg[5];
dtmp = nd.trans - nd.tspec;
setcolor(nd.tdiff, dtmp, dtmp, dtmp);
} else {
nd.tspec = nd.trans = 0.0;
setcolor(nd.tdiff, 0.0, 0.0, 0.0);
}
/* compute reflectance */
dtmp = 1.0 - nd.trans - nd.rspec;
setcolor(nd.rdiff, dtmp, dtmp, dtmp);
nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
multcolor(nd.mcolor, r->pcol); /* modify material color */
multcolor(nd.rdiff, nd.mcolor);
multcolor(nd.tdiff, nd.mcolor);
/* load auxiliary files */
if (hasdata(m->otype)) {
nd.dp = getdata(m->oargs.sarg[1]);
getfunc(m, 2, 0, 0);
} else {
nd.dp = NULL;
getfunc(m, 1, 0, 0);
}
/* compute ambient */
if (nd.trans < 1.0-FTINY) {
copycolor(ctmp, nd.mcolor); /* modified by material color */
scalecolor(ctmp, 1.0-nd.trans);
multambient(ctmp, r, nd.pnorm);
addcolor(r->rcol, ctmp); /* add to returned color */
}
if (nd.trans > FTINY) { /* from other side */
flipsurface(r);
vtmp[0] = -nd.pnorm[0];
vtmp[1] = -nd.pnorm[1];
vtmp[2] = -nd.pnorm[2];
copycolor(ctmp, nd.mcolor);
scalecolor(ctmp, nd.trans);
multambient(ctmp, r, vtmp);
addcolor(r->rcol, ctmp);
flipsurface(r);
}
/* add direct component */
direct(r, dirbrdf, &nd);
return(1);
}
static int
setbrdfunc( /* set up brdf function and variables */
BRDFDAT *np
)
{
FVECT vec;
if (setfunc(np->mp, np->pr) == 0)
return(0); /* it's OK, setfunc says we're done */
/* else (re)assign special variables */
multv3(vec, np->pnorm, funcxf.xfm);
varset("NxP`", '=', vec[0]/funcxf.sca);
varset("NyP`", '=', vec[1]/funcxf.sca);
varset("NzP`", '=', vec[2]/funcxf.sca);
varset("RdotP`", '=', np->pdot <= -1.0 ? -1.0 :
np->pdot >= 1.0 ? 1.0 : np->pdot);
varset("CrP", '=', colval(np->mcolor,RED));
varset("CgP", '=', colval(np->mcolor,GRN));
varset("CbP", '=', colval(np->mcolor,BLU));
return(1);
}

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