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m_mirror.c
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Tue, Apr 30, 20:26

m_mirror.c
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#ifndef lint
static const char RCSid[] = "$Id: m_mirror.c,v 2.22 2020/01/21 21:31:58 greg Exp $";
#endif
/*
* Routines for mirror material supporting virtual light sources
*/
#include "copyright.h"
#include "ray.h"
#include "otypes.h"
#include "rtotypes.h"
#include "source.h"
/*
* The real arguments for MAT_MIRROR are simply:
*
* 3 rrefl grefl brefl
*
* Additionally, the user may specify a single string argument
* which is interpreted as the name of the material to use
* instead of the mirror if the ray being considered is not
* part of the direct calculation.
*/
static int mir_proj(MAT4 pm, OBJREC *o, SRCREC *s, int n);
static void mirrorproj(MAT4 m, FVECT nv, double offs);
VSMATERIAL mirror_vs = {mir_proj, 1};
int
m_mirror( /* shade mirrored ray */
OBJREC *m,
RAY *r
)
{
COLOR mcolor;
RAY nr;
int rpure = 1;
int i;
/* check arguments */
if (m->oargs.nfargs != 3 || m->oargs.nsargs > 1)
objerror(m, USER, "bad number of arguments");
/* check for substitute material */
/* but avoid double-counting */
if ( m->oargs.nsargs > 0 &&
(r->rsrc < 0 || source[r->rsrc].so != r->ro) &&
!(r->crtype & (AMBIENT|SPECULAR) && r->rod > 0.) ) {
if (!strcmp(m->oargs.sarg[0], VOIDID)) {
raytrans(r);
return(1);
}
return(rayshade(r, lastmod(objndx(m), m->oargs.sarg[0])));
}
/* check for bad source ray */
if (r->rsrc >= 0 && source[r->rsrc].so != r->ro)
return(1);
if (r->rod < 0.) { /* back is black */
if (!backvis)
raytrans(r); /* unless back visibility is off */
return(1);
}
/* get modifiers */
raytexture(r, m->omod);
/* assign material color */
setcolor(mcolor, m->oargs.farg[0],
m->oargs.farg[1],
m->oargs.farg[2]);
multcolor(mcolor, r->pcol);
/* compute reflected ray */
if (r->rsrc >= 0) { /* relayed light source */
rayorigin(&nr, REFLECTED, r, mcolor);
/* ignore textures */
for (i = 0; i < 3; i++)
nr.rdir[i] = r->rdir[i] + 2.*r->rod*r->ron[i];
/* source we're aiming for next */
nr.rsrc = source[r->rsrc].sa.sv.sn;
} else { /* ordinary reflection */
FVECT pnorm;
double pdot;
if (rayorigin(&nr, REFLECTED, r, mcolor) < 0)
return(1);
if (!(r->crtype & AMBIENT) &&
DOT(r->pert,r->pert) > FTINY*FTINY) {
pdot = raynormal(pnorm, r); /* use textures */
for (i = 0; i < 3; i++)
nr.rdir[i] = r->rdir[i] + 2.*pdot*pnorm[i];
rpure = 0;
}
/* check for penetration */
if (rpure || DOT(nr.rdir, r->ron) <= FTINY)
for (i = 0; i < 3; i++)
nr.rdir[i] = r->rdir[i] + 2.*r->rod*r->ron[i];
}
checknorm(nr.rdir);
rayvalue(&nr);
multcolor(nr.rcol, nr.rcoef);
copycolor(r->mcol, nr.rcol);
addcolor(r->rcol, nr.rcol);
r->rmt = r->rot;
if (rpure && r->ro != NULL && isflat(r->ro->otype))
r->rmt += raydistance(&nr);
return(1);
}
static int
mir_proj( /* compute a mirror's projection */
MAT4 pm,
OBJREC *o,
SRCREC *s,
int n
)
{
double corr = 1.;
FVECT nv, sc;
double od, offs;
int i;
/* get surface normal and offset */
offs = od = getplaneq(nv, o);
if (s->sflags & SDISTANT)
offs = 0.;
/* check for extreme point behind */
if (s->sflags & SCIR) {
if (s->sflags & (SFLAT|SDISTANT))
corr = 1.12837917; /* correct setflatss() */
else
corr = 1.0/0.7236; /* correct sphsetsrc() */
}
VCOPY(sc, s->sloc);
for (i = s->sflags & SFLAT ? SV : SW; i >= 0; i--)
if (DOT(nv, s->ss[i]) > offs)
VSUM(sc, sc, s->ss[i], corr);
else
VSUM(sc, sc, s->ss[i], -corr);
if (DOT(sc, nv) <= offs+FTINY)
return(0);
/* everything OK -- compute projection */
mirrorproj(pm, nv, od);
return(1);
}
static void
mirrorproj( /* get mirror projection for surface */
MAT4 m,
FVECT nv,
double offs
)
{
int i, j;
/* assign matrix */
setident4(m);
for (j = 0; j < 3; j++) {
for (i = 0; i < 3; i++)
m[i][j] -= 2.*nv[i]*nv[j];
m[3][j] = 2.*offs*nv[j];
}
}

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