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/* Copyright (c) 1986 Regents of the University of California */ |
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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* dielectric.c - shading function for transparent materials. |
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* |
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* 9/6/85 |
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*/ |
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#include "ray.h" |
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#include "copyright.h" |
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#include "ray.h" |
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#include "otypes.h" |
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#include "rtotypes.h" |
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#ifdef DISPERSE |
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#include "source.h" |
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static disperse(); |
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static int lambda(); |
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static int disperse(OBJREC *m,RAY *r,FVECT vt,double tr,COLOR cet,COLOR abt); |
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static int lambda(OBJREC *m, FVECT v2, FVECT dv, FVECT lr); |
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#endif |
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static double mylog(double x); |
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/* |
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* Explicit calculations for Fresnel's equation are performed, |
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* but only one square root computation is necessary. |
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#define MINCOS 0.997 /* minimum dot product for dispersion */ |
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extern COLOR cextinction; /* global coefficient of extinction */ |
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extern COLOR salbedo; /* global scattering albedo */ |
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static double |
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mylog(x) /* special log for extinction coefficients */ |
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double x; |
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mylog( /* special log for extinction coefficients */ |
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double x |
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) |
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{ |
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if (x < 1e-40) |
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return(-100.); |
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} |
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m_dielectric(m, r) /* color a ray which hit a dielectric interface */ |
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OBJREC *m; |
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register RAY *r; |
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extern int |
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m_dielectric( /* color a ray which hit a dielectric interface */ |
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OBJREC *m, |
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register RAY *r |
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) |
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{ |
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double cos1, cos2, nratio; |
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COLOR ctrans; |
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COLOR talb; |
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double mabsorp; |
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int hastexture; |
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double transdist, transtest=0; |
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double mirdist, mirtest=0; |
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int flatsurface; |
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double refl, trans; |
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FVECT dnorm; |
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double d1, d2; |
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raytexture(r, m->omod); /* get modifiers */ |
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cos1 = raynormal(dnorm, r); /* cosine of theta1 */ |
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if ( (hastexture = DOT(r->pert,r->pert) > FTINY*FTINY) ) |
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cos1 = raynormal(dnorm, r); /* perturb normal */ |
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else { |
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VCOPY(dnorm, r->ron); |
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cos1 = r->rod; |
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} |
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flatsurface = !hastexture && r->ro != NULL && isflat(r->ro->otype); |
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/* index of refraction */ |
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if (m->otype == MAT_DIELECTRIC) |
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nratio = m->oargs.farg[3] + m->oargs.farg[4]/MLAMBDA; |
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nratio = m->oargs.farg[3] / m->oargs.farg[7]; |
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if (cos1 < 0.0) { /* inside */ |
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hastexture = -hastexture; |
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cos1 = -cos1; |
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dnorm[0] = -dnorm[0]; |
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dnorm[1] = -dnorm[1]; |
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r->gecc = 0.; |
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} |
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} |
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/* estimate absorption */ |
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mabsorp = colval(r->cext,RED) < colval(r->cext,GRN) ? |
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colval(r->cext,RED) : colval(r->cext,GRN); |
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if (colval(r->cext,BLU) < mabsorp) mabsorp = colval(r->cext,BLU); |
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if (mabsorp > 0.) |
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mabsorp = exp(-mabsorp*r->rot); /* conservative */ |
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else |
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mabsorp = 1.0; |
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d2 = 1.0 - nratio*nratio*(1.0 - cos1*cos1); /* compute cos theta2 */ |
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refl *= 0.5; |
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trans = 1.0 - refl; |
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if (rayorigin(&p, r, REFRACTED, mabsorp*trans) == 0) { |
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trans *= nratio*nratio; /* solid angle ratio */ |
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if (rayorigin(&p, r, REFRACTED, trans) == 0) { |
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/* compute refracted ray */ |
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d1 = nratio*cos1 - cos2; |
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for (i = 0; i < 3; i++) |
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p.rdir[i] = nratio*r->rdir[i] + d1*dnorm[i]; |
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/* accidental reflection? */ |
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if (hastexture && |
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DOT(p.rdir,r->ron)*hastexture >= -FTINY) { |
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d1 *= (double)hastexture; |
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for (i = 0; i < 3; i++) /* ignore texture */ |
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p.rdir[i] = nratio*r->rdir[i] + |
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d1*r->ron[i]; |
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normalize(p.rdir); /* not exact */ |
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} |
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#ifdef DISPERSE |
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if (m->otype != MAT_DIELECTRIC |
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|| r->rod > 0.0 |
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rayvalue(&p); |
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scalecolor(p.rcol, trans); |
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addcolor(r->rcol, p.rcol); |
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if (nratio >= 1.0-FTINY && nratio <= 1.0+FTINY) |
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r->rt = r->rot + p.rt; |
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/* virtual distance */ |
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if (flatsurface || |
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(1.-FTINY <= nratio && |
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nratio <= 1.+FTINY)) { |
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transtest = 2*bright(p.rcol); |
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transdist = r->rot + p.rt; |
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} |
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} |
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} |
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} |
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if (!(r->crtype & SHADOW) && |
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rayorigin(&p, r, REFLECTED, mabsorp*refl) == 0) { |
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rayorigin(&p, r, REFLECTED, refl) == 0) { |
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/* compute reflected ray */ |
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for (i = 0; i < 3; i++) |
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p.rdir[i] = r->rdir[i] + 2.0*cos1*dnorm[i]; |
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/* accidental penetration? */ |
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if (hastexture && DOT(p.rdir,r->ron)*hastexture <= FTINY) |
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for (i = 0; i < 3; i++) /* ignore texture */ |
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p.rdir[i] = r->rdir[i] + 2.0*r->rod*r->ron[i]; |
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rayvalue(&p); /* reflected ray value */ |
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scalecolor(p.rcol, refl); /* color contribution */ |
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addcolor(r->rcol, p.rcol); |
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/* virtual distance */ |
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if (flatsurface) { |
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mirtest = 2*bright(p.rcol); |
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mirdist = r->rot + p.rt; |
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} |
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} |
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/* check distance to return */ |
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d1 = bright(r->rcol); |
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if (transtest > d1) |
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r->rt = transdist; |
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else if (mirtest > d1) |
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r->rt = mirdist; |
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/* rayvalue() computes absorption */ |
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return(1); |
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} |
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#ifdef DISPERSE |
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static |
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disperse(m, r, vt, tr, cet, abt) /* check light sources for dispersion */ |
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OBJREC *m; |
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RAY *r; |
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FVECT vt; |
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double tr; |
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COLOR cet, abt; |
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static int |
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disperse( /* check light sources for dispersion */ |
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OBJREC *m, |
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RAY *r, |
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FVECT vt, |
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double tr, |
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COLOR cet, |
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COLOR abt |
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) |
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{ |
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RAY sray, *entray; |
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FVECT v1, v2, n1, n2; |
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static int |
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lambda(m, v2, dv, lr) /* compute lambda for material */ |
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register OBJREC *m; |
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FVECT v2, dv, lr; |
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lambda( /* compute lambda for material */ |
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register OBJREC *m, |
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FVECT v2, |
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FVECT dv, |
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FVECT lr |
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) |
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{ |
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FVECT lrXdv, v2Xlr; |
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double dtmp, denom; |
