src/rt/m_brdf.c

/* Copyright (c) 1990 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 *  Shading for materials with arbitrary BRDF's
 */

#include  "ray.h"

#include  "data.h"

#include  "otypes.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.
 *      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 ..
 */

extern double   funvalue(), varvalue();

typedef struct {
        OBJREC  *mp;            /* material pointer */
        RAY  *pr;               /* intersected ray */
        DATARRAY  *dp;          /* data array for PDATA or MDATA */
        COLOR  mcolor;          /* color of this material */
        COLOR  scolor;          /* color of specular component */
        double  rspec;          /* specular reflection */
        double  rdiff;          /* diffuse reflection */
        FVECT  pnorm;           /* perturbed surface normal */
        double  pdot;           /* perturbed dot product */
}  BRDFDAT;             /* BRDF material data */


dirbrdf(cval, np, ldir, omega)          /* compute source contribution */
COLOR  cval;                    /* returned coefficient */
register BRDFDAT  *np;          /* material data */
FVECT  ldir;                    /* light source direction */
double  omega;                  /* light source size */
{
        extern XF  funcxf;
        double  ldot;
        double  dtmp;
        COLOR  ctmp;
        FVECT  ldx;
        double  pt[MAXDIM];
        register int    i;

        setcolor(cval, 0.0, 0.0, 0.0);
        
        ldot = DOT(np->pnorm, ldir);

        if (ldot < 0.0)
                return;         /* wrong side */

        if (np->rdiff > FTINY) {
                /*
                 *  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->mcolor);
                dtmp = ldot * omega * np->rdiff / PI;
                scalecolor(ctmp, dtmp);
                addcolor(cval, ctmp);
        }
        if (np->rspec > FTINY) {
                /*
                 *  Compute specular component.
                 */
                setfunc(np->mp, np->pr);
                                                /* transform light vector */
                multv3(ldx, ldir, funcxf.xfm);
                for (i = 0; i < 3; i++)
                        ldx[i] /= funcxf.sca;
                                                /* evaluate BRDF */
                errno = 0;
                if (np->dp == NULL)
                        dtmp = funvalue(np->mp->oargs.sarg[0], 3, ldx);
                else {
                        for (i = 0; i < np->dp->nd; i++)
                                pt[i] = funvalue(np->mp->oargs.sarg[3+i],
                                                3, ldx);
                        dtmp = datavalue(np->dp, pt);
                        dtmp = funvalue(np->mp->oargs.sarg[0], 1, &dtmp);
                }
                if (errno)
                        goto computerr;
                if (dtmp > FTINY) {
                        copycolor(ctmp, np->scolor);
                        dtmp *= ldot * omega;
                        scalecolor(ctmp, dtmp);
                        addcolor(cval, ctmp);
                }
        }
        return;
computerr:
        objerror(np->mp, WARNING, "compute error");
        return;
}


m_brdf(m, r)                    /* color a ray which hit a BRDF material */
register OBJREC  *m;
register RAY  *r;
{
        BRDFDAT  nd;
        COLOR  ctmp;
        register int  i;

        if (m->oargs.nsargs < 2 || m->oargs.nfargs < 4)
                objerror(m, USER, "bad # arguments");
                                                /* easy shadow test */
        if (r->crtype & SHADOW)
                return;
        nd.mp = m;
        nd.pr = r;
                                                /* load auxiliary files */
        if (m->otype == MAT_PDATA || m->otype == MAT_MDATA) {
                nd.dp = getdata(m->oargs.sarg[1]);
                for (i = 3; i < m->oargs.nsargs; i++)
                        if (m->oargs.sarg[i][0] == '-')
                                break;
                if (i-3 != nd.dp->nd)
                        objerror(m, USER, "dimension error");
                if (!fundefined(m->oargs.sarg[3]))
                        loadfunc(m->oargs.sarg[2]);
        } else {
                nd.dp = NULL;
                if (!fundefined(m->oargs.sarg[0]))
                        loadfunc(m->oargs.sarg[1]);
        }
                                                /* get material color */
        setcolor(nd.mcolor, m->oargs.farg[0],
                           m->oargs.farg[1],
                           m->oargs.farg[2]);
                                                /* get roughness */
        if (r->rod < 0.0)
                flipsurface(r);
                                                /* get modifiers */
        raytexture(r, m->omod);
        nd.pdot = raynormal(nd.pnorm, r);       /* perturb normal */
        multcolor(nd.mcolor, r->pcol);          /* modify material color */
        r->rt = r->rot;                         /* default ray length */
                                                /* get specular component */
        nd.rspec = m->oargs.farg[3];

        if (nd.rspec > FTINY) {                 /* has specular component */
                                                /* compute specular color */
                if (m->otype == MAT_MFUNC || m->otype == MAT_MDATA)
                        copycolor(nd.scolor, nd.mcolor);
                else
                        setcolor(nd.scolor, 1.0, 1.0, 1.0);
                scalecolor(nd.scolor, nd.rspec);
        }
                                                /* diffuse reflection */
        nd.rdiff = 1.0 - nd.rspec;
                                                /* compute ambient */
        if (nd.rdiff > FTINY) {
                ambient(ctmp, r);
                multcolor(ctmp, nd.mcolor);     /* modified by material color */
                addcolor(r->rcol, ctmp);        /* add to returned color */
        }
                                                /* add direct component */
        direct(r, dirbrdf, &nd);
}
Revision:	1.4
Committed:	Sat Dec 15 15:03:44 1990 UTC (34 years, 10 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.3:	+13 -7 lines
Log Message:	changed handling of matrix transformations with new MAT4 & XF types dynamic allocation of ray transformations with newrayxf() added missing light source vector transformation to m_brdf.c
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1990 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Shading for materials with arbitrary BRDF's
9			*/
10
11			#include "ray.h"
12
13			#include "data.h"
14
15			#include "otypes.h"
16
17			/*
18			* Arguments to this material include the color and specularity.
19			* String arguments include the reflection function and files.
20			* The BRDF is currently used just for the specular component to light
21			* sources. Reflectance values or data coordinates are functions
22			* of the direction to the light source.
23			* We orient the surface towards the incoming ray, so a single
24			* surface can be used to represent an infinitely thin object.
25			*
26			* Arguments for MAT_PFUNC and MAT_MFUNC are:
27	greg	1.4	* 2+ func funcfile transform
28	greg	1.1	* 0
29	greg	1.4	* 4+ red grn blu specularity A5 ..
30	greg	1.1	*
31			* Arguments for MAT_PDATA and MAT_MDATA are:
32	greg	1.4	* 4+ func datafile funcfile v0 .. transform
33	greg	1.1	* 0
34	greg	1.4	* 4+ red grn blu specularity A5 ..
35	greg	1.1	*/
36
37	greg	1.2	extern double funvalue(), varvalue();
38
39	greg	1.1	typedef struct {
40			OBJREC mp; / material pointer */
41			RAY pr; / intersected ray */
42			DATARRAY dp; / data array for PDATA or MDATA */
43			COLOR mcolor; /* color of this material */
44			COLOR scolor; /* color of specular component */
45			double rspec; /* specular reflection */
46			double rdiff; /* diffuse reflection */
47			FVECT pnorm; /* perturbed surface normal */
48			double pdot; /* perturbed dot product */
49			} BRDFDAT; /* BRDF material data */
50
51
52			dirbrdf(cval, np, ldir, omega) /* compute source contribution */
53			COLOR cval; /* returned coefficient */
54			register BRDFDAT np; / material data */
55			FVECT ldir; /* light source direction */
56			double omega; /* light source size */
57			{
58	greg	1.4	extern XF funcxf;
59	greg	1.1	double ldot;
60			double dtmp;
61			COLOR ctmp;
62	greg	1.4	FVECT ldx;
63	greg	1.1	double pt[MAXDIM];
64			register int i;
65
66			setcolor(cval, 0.0, 0.0, 0.0);
67
68			ldot = DOT(np->pnorm, ldir);
69
70			if (ldot < 0.0)
71			return; /* wrong side */
72
73			if (np->rdiff > FTINY) {
74			/*
75			* Compute and add diffuse reflected component to returned
76			* color. The diffuse reflected component will always be
77			* modified by the color of the material.
78			*/
79			copycolor(ctmp, np->mcolor);
80			dtmp = ldot * omega * np->rdiff / PI;
81			scalecolor(ctmp, dtmp);
82			addcolor(cval, ctmp);
83			}
84			if (np->rspec > FTINY) {
85			/*
86			* Compute specular component.
87			*/
88			setfunc(np->mp, np->pr);
89	greg	1.4	/* transform light vector */
90			multv3(ldx, ldir, funcxf.xfm);
91			for (i = 0; i < 3; i++)
92			ldx[i] /= funcxf.sca;
93			/* evaluate BRDF */
94	greg	1.1	errno = 0;
95			if (np->dp == NULL)
96	greg	1.4	dtmp = funvalue(np->mp->oargs.sarg[0], 3, ldx);
97	greg	1.1	else {
98			for (i = 0; i < np->dp->nd; i++)
99			pt[i] = funvalue(np->mp->oargs.sarg[3+i],
100	greg	1.4	3, ldx);
101	greg	1.1	dtmp = datavalue(np->dp, pt);
102			dtmp = funvalue(np->mp->oargs.sarg[0], 1, &dtmp);
103			}
104			if (errno)
105			goto computerr;
106			if (dtmp > FTINY) {
107			copycolor(ctmp, np->scolor);
108			dtmp = ldot omega;
109			scalecolor(ctmp, dtmp);
110			addcolor(cval, ctmp);
111			}
112			}
113			return;
114			computerr:
115			objerror(np->mp, WARNING, "compute error");
116			return;
117			}
118
119
120			m_brdf(m, r) /* color a ray which hit a BRDF material */
121			register OBJREC *m;
122			register RAY *r;
123			{
124			BRDFDAT nd;
125			COLOR ctmp;
126			register int i;
127
128			if (m->oargs.nsargs < 2 \|\| m->oargs.nfargs < 4)
129			objerror(m, USER, "bad # arguments");
130			/* easy shadow test */
131			if (r->crtype & SHADOW)
132			return;
133			nd.mp = m;
134			nd.pr = r;
135			/* load auxiliary files */
136			if (m->otype == MAT_PDATA \|\| m->otype == MAT_MDATA) {
137			nd.dp = getdata(m->oargs.sarg[1]);
138			for (i = 3; i < m->oargs.nsargs; i++)
139			if (m->oargs.sarg[i][0] == '-')
140			break;
141			if (i-3 != nd.dp->nd)
142			objerror(m, USER, "dimension error");
143			if (!fundefined(m->oargs.sarg[3]))
144			loadfunc(m->oargs.sarg[2]);
145			} else {
146			nd.dp = NULL;
147			if (!fundefined(m->oargs.sarg[0]))
148			loadfunc(m->oargs.sarg[1]);
149			}
150			/* get material color */
151			setcolor(nd.mcolor, m->oargs.farg[0],
152			m->oargs.farg[1],
153			m->oargs.farg[2]);
154			/* get roughness */
155			if (r->rod < 0.0)
156			flipsurface(r);
157			/* get modifiers */
158			raytexture(r, m->omod);
159			nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
160			multcolor(nd.mcolor, r->pcol); /* modify material color */
161			r->rt = r->rot; /* default ray length */
162			/* get specular component */
163			nd.rspec = m->oargs.farg[3];
164
165			if (nd.rspec > FTINY) { /* has specular component */
166			/* compute specular color */
167			if (m->otype == MAT_MFUNC \|\| m->otype == MAT_MDATA)
168			copycolor(nd.scolor, nd.mcolor);
169			else
170			setcolor(nd.scolor, 1.0, 1.0, 1.0);
171			scalecolor(nd.scolor, nd.rspec);
172			}
173			/* diffuse reflection */
174			nd.rdiff = 1.0 - nd.rspec;
175			/* compute ambient */
176			if (nd.rdiff > FTINY) {
177			ambient(ctmp, r);
178			multcolor(ctmp, nd.mcolor); /* modified by material color */
179			addcolor(r->rcol, ctmp); /* add to returned color */
180			}
181			/* add direct component */
182			direct(r, dirbrdf, &nd);
183			}