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#ifndef lint |
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static const char RCSid[] = "$Id: ashikhmin.c,v 2.4 2014/12/04 05:26:28 greg Exp $"; |
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#endif |
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/* |
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* Shading functions for Ashikhmin-Shirley anisotropic materials. |
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*/ |
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|
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#include "copyright.h" |
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|
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#include "ray.h" |
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#include "ambient.h" |
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#include "otypes.h" |
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#include "rtotypes.h" |
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#include "source.h" |
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#include "func.h" |
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#include "random.h" |
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|
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#ifndef MAXITER |
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#define MAXITER 10 /* maximum # specular ray attempts */ |
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#endif |
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|
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/* |
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* Ashikhmin-Shirley model |
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* |
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* Arguments for MAT_ASHIKHMIN are: |
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* 4+ ux uy uz funcfile [transform...] |
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* 0 |
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* 8 dred dgrn dblu sred sgrn sblu u-power v-power |
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*/ |
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|
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/* specularity flags */ |
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#define SPA_REFL 01 /* has reflected specular component */ |
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#define SPA_FLAT 02 /* reflecting surface is flat */ |
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#define SPA_RBLT 010 /* reflection below sample threshold */ |
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|
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typedef struct { |
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OBJREC *mp; /* material pointer */ |
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RAY *rp; /* ray pointer */ |
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short specfl; /* specularity flags, defined above */ |
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COLOR mcolor; /* color of this material */ |
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COLOR scolor; /* color of specular component */ |
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FVECT u, v; /* u and v vectors orienting anisotropy */ |
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double u_power; /* u power */ |
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double v_power; /* v power */ |
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FVECT pnorm; /* perturbed surface normal */ |
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double pdot; /* perturbed dot product */ |
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} ASHIKDAT; /* anisotropic material data */ |
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|
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static void getacoords_as(ASHIKDAT *np); |
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static void ashiksamp(ASHIKDAT *np); |
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|
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#undef MAX |
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#define MAX(a,b) ((a)>(b) ? (a) : (b)) |
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|
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|
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static double |
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schlick_fres(double dprod) |
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{ |
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double pf = 1. - dprod; |
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|
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return(pf*pf*pf*pf*pf); |
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} |
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|
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|
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static void |
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dirashik( /* compute source contribution */ |
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COLOR cval, /* returned coefficient */ |
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void *nnp, /* material data */ |
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FVECT ldir, /* light source direction */ |
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double omega /* light source size */ |
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) |
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{ |
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ASHIKDAT *np = nnp; |
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double ldot; |
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double dtmp, dtmp1, dtmp2; |
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FVECT h; |
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COLOR ctmp; |
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|
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setcolor(cval, 0.0, 0.0, 0.0); |
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|
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ldot = DOT(np->pnorm, ldir); |
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|
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if (ldot < 0.0) |
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return; /* wrong side */ |
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|
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/* |
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* Compute and add diffuse reflected component to returned |
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* color. |
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*/ |
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copycolor(ctmp, np->mcolor); |
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dtmp = ldot * omega * (1.0/PI) * (1. - schlick_fres(ldot)); |
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scalecolor(ctmp, dtmp); |
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addcolor(cval, ctmp); |
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|
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if (!(np->specfl & SPA_REFL)) |
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return; |
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/* |
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* Compute specular reflection coefficient |
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*/ |
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/* half vector */ |
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VSUB(h, ldir, np->rp->rdir); |
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normalize(h); |
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/* ellipse */ |
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dtmp1 = DOT(np->u, h); |
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dtmp1 *= dtmp1 * np->u_power; |
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dtmp2 = DOT(np->v, h); |
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dtmp2 *= dtmp2 * np->v_power; |
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/* Ashikhmin-Shirley model*/ |
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dtmp = DOT(np->pnorm, h); |
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dtmp = pow(dtmp, (dtmp1+dtmp2)/(1.-dtmp*dtmp)); |
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dtmp *= sqrt((np->u_power+1.)*(np->v_power+1.)); |
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dtmp /= 8.*PI * DOT(ldir,h) * MAX(ldot,np->pdot); |
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/* worth using? */ |
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if (dtmp > FTINY) { |
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copycolor(ctmp, np->scolor); |
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dtmp *= ldot * omega; |
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scalecolor(ctmp, dtmp); |
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addcolor(cval, ctmp); |
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} |
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} |
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|
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|
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int |
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m_ashikhmin( /* shade ray that hit something anisotropic */ |
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OBJREC *m, |
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RAY *r |
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) |
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{ |
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ASHIKDAT nd; |
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COLOR ctmp; |
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double fres; |
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int i; |
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/* easy shadow test */ |
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if (r->crtype & SHADOW) |
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return(1); |
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|
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if (m->oargs.nfargs != 8) |
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objerror(m, USER, "bad number of real arguments"); |
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/* check for back side */ |
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if (r->rod < 0.0) { |
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if (!backvis) { |
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raytrans(r); |
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return(1); |
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} |
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raytexture(r, m->omod); |
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flipsurface(r); /* reorient if backvis */ |
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} else |
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raytexture(r, m->omod); |
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/* get material color */ |
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nd.mp = m; |
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nd.rp = r; |
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setcolor(nd.mcolor, m->oargs.farg[0], |
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m->oargs.farg[1], |
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m->oargs.farg[2]); |
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setcolor(nd.scolor, m->oargs.farg[3], |
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m->oargs.farg[4], |
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m->oargs.farg[5]); |
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/* get specular power */ |
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nd.specfl = 0; |
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nd.u_power = m->oargs.farg[6]; |
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nd.v_power = m->oargs.farg[7]; |
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|
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nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */ |
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if (nd.pdot < .001) |
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nd.pdot = .001; /* non-zero for dirashik() */ |
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multcolor(nd.mcolor, r->pcol); /* modify diffuse color */ |
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|
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if (bright(nd.scolor) > FTINY) { /* adjust specular color */ |
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nd.specfl |= SPA_REFL; |
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/* check threshold */ |
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if (specthresh >= bright(nd.scolor)-FTINY) |
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nd.specfl |= SPA_RBLT; |
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fres = schlick_fres(nd.pdot); /* Schick's Fresnel approx */ |
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for (i = 0; i < 3; i++) |
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colval(nd.scolor,i) += (1.-colval(nd.scolor,i))*fres; |
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} |
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if (r->ro != NULL && isflat(r->ro->otype)) |
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nd.specfl |= SPA_FLAT; |
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/* set up coordinates */ |
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getacoords_as(&nd); |
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/* specular sampling? */ |
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if ((nd.specfl & (SPA_REFL|SPA_RBLT)) == SPA_REFL) |
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ashiksamp(&nd); |
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/* diffuse interreflection */ |
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if (bright(nd.mcolor) > FTINY) { |
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copycolor(ctmp, nd.mcolor); /* modified by material color */ |
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if (nd.specfl & SPA_RBLT) /* add in specular as well? */ |
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addcolor(ctmp, nd.scolor); |
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multambient(ctmp, r, nd.pnorm); |
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addcolor(r->rcol, ctmp); /* add to returned color */ |
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} |
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direct(r, dirashik, &nd); /* add direct component */ |
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|
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return(1); |
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} |
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|
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|
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static void |
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getacoords_as( /* set up coordinate system */ |
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ASHIKDAT *np |
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) |
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{ |
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MFUNC *mf; |
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int i; |
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|
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mf = getfunc(np->mp, 3, 0x7, 1); |
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setfunc(np->mp, np->rp); |
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errno = 0; |
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for (i = 0; i < 3; i++) |
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np->u[i] = evalue(mf->ep[i]); |
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if ((errno == EDOM) | (errno == ERANGE)) |
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np->u[0] = np->u[1] = np->u[2] = 0.0; |
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if (mf->fxp != &unitxf) |
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multv3(np->u, np->u, mf->fxp->xfm); |
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fcross(np->v, np->pnorm, np->u); |
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if (normalize(np->v) == 0.0) { |
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if (fabs(np->u_power - np->v_power) > 0.1) |
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objerror(np->mp, WARNING, "bad orientation vector"); |
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getperpendicular(np->u, np->pnorm, 1); /* punting */ |
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fcross(np->v, np->pnorm, np->u); |
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np->u_power = np->v_power = |
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2./(1./(np->u_power+1e-5) + 1./(np->v_power+1e-5)); |
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} else |
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fcross(np->u, np->v, np->pnorm); |
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} |
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|
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|
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static void |
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ashiksamp( /* sample anisotropic Ashikhmin-Shirley specular */ |
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ASHIKDAT *np |
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) |
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{ |
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RAY sr; |
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FVECT h; |
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double rv[2], dtmp; |
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double cosph, sinph, costh, sinth; |
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int maxiter, ntrials, nstarget, nstaken; |
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int i; |
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|
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if (rayorigin(&sr, SPECULAR, np->rp, np->scolor) < 0) |
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return; |
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|
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nstarget = 1; |
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if (specjitter > 1.5) { /* multiple samples? */ |
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nstarget = specjitter*np->rp->rweight + .5; |
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if (sr.rweight <= minweight*nstarget) |
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nstarget = sr.rweight/minweight; |
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if (nstarget > 1) { |
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dtmp = 1./nstarget; |
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scalecolor(sr.rcoef, dtmp); |
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sr.rweight *= dtmp; |
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} else |
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nstarget = 1; |
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} |
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dimlist[ndims++] = (int)(size_t)np->mp; |
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maxiter = MAXITER*nstarget; |
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for (nstaken = ntrials = 0; nstaken < nstarget && |
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ntrials < maxiter; ntrials++) { |
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if (ntrials) |
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dtmp = frandom(); |
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else |
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dtmp = urand(ilhash(dimlist,ndims)+647+samplendx); |
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multisamp(rv, 2, dtmp); |
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dtmp = 2.*PI * rv[0]; |
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cosph = sqrt(np->v_power + 1.) * tcos(dtmp); |
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sinph = sqrt(np->u_power + 1.) * tsin(dtmp); |
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dtmp = 1./sqrt(cosph*cosph + sinph*sinph); |
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cosph *= dtmp; |
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sinph *= dtmp; |
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costh = pow(rv[1], 1./(np->u_power*cosph*cosph+np->v_power*sinph*sinph+1.)); |
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if (costh <= FTINY) |
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continue; |
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sinth = sqrt(1. - costh*costh); |
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for (i = 0; i < 3; i++) |
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h[i] = cosph*sinth*np->u[i] + sinph*sinth*np->v[i] + costh*np->pnorm[i]; |
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|
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if (nstaken) |
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rayclear(&sr); |
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dtmp = -2.*DOT(h, np->rp->rdir); |
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VSUM(sr.rdir, np->rp->rdir, h, dtmp); |
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/* sample rejection test */ |
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if (DOT(sr.rdir, np->rp->ron) <= FTINY) |
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continue; |
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checknorm(sr.rdir); |
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rayvalue(&sr); |
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multcolor(sr.rcol, sr.rcoef); |
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addcolor(np->rp->rcol, sr.rcol); |
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++nstaken; |
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} |
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ndims--; |
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} |
