static AMBHEMI *
samp_hemi( /* sample indirect hemisphere */
COLOR rcol,
RAY *r,
double wt
)
{
AMBHEMI *hp;
double d;
int n, i, j;
/* insignificance check */
if (bright(rcol) <= FTINY)
return(NULL);
/* set number of divisions */
if (ambacc <= FTINY &&
wt > (d = 0.8*intens(rcol)*r->rweight/(ambdiv*minweight)))
wt = d; /* avoid ray termination */
n = sqrt(ambdiv * wt) + 0.5;
i = 1 + 5*(ambacc > FTINY); /* minimum number of samples */
if (n < i)
n = i;
/* allocate sampling array */
hp = (AMBHEMI *)malloc(sizeof(AMBHEMI) + sizeof(AMBSAMP)*(n*n - 1));
if (hp == NULL)
error(SYSTEM, "out of memory in samp_hemi");
hp->rp = r;
hp->ns = n;
hp->acol[RED] = hp->acol[GRN] = hp->acol[BLU] = 0.0;
memset(hp->sa, 0, sizeof(AMBSAMP)*n*n);
hp->sampOK = 0;
/* assign coefficient */
copycolor(hp->acoef, rcol);
d = 1.0/(n*n);
scalecolor(hp->acoef, d);
/* make tangent plane axes */
if (!getperpendicular(hp->ux, r->ron, 1))
error(CONSISTENCY, "bad ray direction in samp_hemi");
VCROSS(hp->uy, r->ron, hp->ux);
/* sample divisions */
for (i = hp->ns; i--; )
for (j = hp->ns; j--; )
hp->sampOK += ambsample(hp, i, j, 0);
copycolor(rcol, hp->acol);
if (!hp->sampOK) { /* utter failure? */
free(hp);
return(NULL);
}
if (hp->sampOK < hp->ns*hp->ns) {
hp->sampOK *= -1; /* soft failure */
return(hp);
}
if (hp->sampOK < 64)
return(hp); /* insufficient for super-sampling */
n = ambssamp*wt + 0.5;
if (n > 8) { /* perform super-sampling? */
ambsupersamp(hp, n);
copycolor(rcol, hp->acol);
}
return(hp); /* all is well */
}
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); /* 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);
}
