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root/radiance/ray/src/rt/m_bsdf.c
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Comparing ray/src/rt/m_bsdf.c (file contents):
Revision 2.34 by greg, Mon May 15 22:50:33 2017 UTC vs.
Revision 2.38 by greg, Fri May 19 15:13:41 2017 UTC

# Line 23 | Line 23 | static const char RCSid[] = "$Id$";
23   *  (opposite the surface normal) to bypass any intervening geometry.
24   *  Translation only affects scattered, non-source-directed samples.
25   *  A non-zero thickness has the further side-effect that an unscattered
26 < *  (view) ray will pass right through our material if it has any
27 < *  non-diffuse transmission, making the BSDF surface invisible.  This
28 < *  shows the proxied geometry instead. Thickness has the further
29 < *  effect of turning off reflection on the hidden side so that rays
30 < *  heading in the opposite direction pass unimpeded through the BSDF
26 > *  (view) ray will pass right through our material, making the BSDF
27 > *  surface invisible and showing the proxied geometry instead. Thickness
28 > *  has the further effect of turning off reflection on the reverse side so
29 > *  rays heading in the opposite direction pass unimpeded through the BSDF
30   *  surface.  A paired surface may be placed on the opposide side of
31   *  the detail geometry, less than this thickness away, if a two-way
32   *  proxy is desired.  Note that the sign of the thickness is important.
# Line 36 | Line 35 | static const char RCSid[] = "$Id$";
35   *  hides geometry in front of the surface when rays hit from behind,
36   *  and applies only the transmission and backside reflectance properties.
37   *  Reflection is ignored on the hidden side, as those rays pass through.
38 + *      When thickness is set to zero, shadow rays will be blocked unless
39 + *  a BTDF has a strong "through" component in the source direction.
40 + *  A separate test prevents over-counting by dropping specular & ambient
41 + *  samples that are too close to this "through" direction.  The same
42 + *  restriction applies for the proxy case (thickness != 0).
43   *      The "up" vector for the BSDF is given by three variables, defined
44   *  (along with the thickness) by the named function file, or '.' if none.
45   *  Together with the surface normal, this defines the local coordinate
# Line 43 | Line 47 | static const char RCSid[] = "$Id$";
47   *      We do not reorient the surface, so if the BSDF has no back-side
48   *  reflectance and none is given in the real arguments, a BSDF surface
49   *  with zero thickness will appear black when viewed from behind
50 < *  unless backface visibility is off.
50 > *  unless backface visibility is on, when it becomes invisible.
51   *      The diffuse arguments are added to components in the BSDF file,
52   *  not multiplied.  However, patterns affect this material as a multiplier
53   *  on everything except non-diffuse reflection.
# Line 59 | Line 63 | static const char RCSid[] = "$Id$";
63   /*
64   * Note that our reverse ray-tracing process means that the positions
65   * of incoming and outgoing vectors may be reversed in our calls
66 < * to the BSDF library.  This is fine, since the bidirectional nature
66 > * to the BSDF library.  This is usually fine, since the bidirectional nature
67   * of the BSDF (that's what the 'B' stands for) means it all works out.
68   */
69  
# Line 72 | Line 76 | typedef struct {
76          RREAL   toloc[3][3];    /* world to local BSDF coords */
77          RREAL   fromloc[3][3];  /* local BSDF coords to world */
78          double  thick;          /* surface thickness */
79 <        COLOR   cthru;          /* through component multiplier */
79 >        COLOR   cthru;          /* "through" component multiplier */
80          SDData  *sd;            /* loaded BSDF data */
81          COLOR   rdiff;          /* diffuse reflection */
82          COLOR   tdiff;          /* diffuse transmission */
# Line 80 | Line 84 | typedef struct {
84  
85   #define cvt_sdcolor(cv, svp)    ccy2rgb(&(svp)->spec, (svp)->cieY, cv)
86  
87 < /* Compute through component color */
87 > /* Compute "through" component color */
88   static void
89   compute_through(BSDFDAT *ndp)
90   {
# Line 110 | Line 114 | compute_through(BSDFDAT *ndp)
114  
115          setcolor(ndp->cthru, .0, .0, .0);       /* starting assumption */
116  
117 +        if (!(ndp->pr->crtype & (SPECULAR|AMBIENT|SHADOW)))
118 +                return;                         /* simply don't need to know */
119 +
120          if (ndp->pr->rod > 0)
121                  dfp = (ndp->sd->tf != NULL) ? ndp->sd->tf : ndp->sd->tb;
122          else
# Line 130 | Line 137 | compute_through(BSDFDAT *ndp)
137                  tdir[0] = -ndp->vray[0] + dir2check[i][0]*srchrad;
138                  tdir[1] = -ndp->vray[1] + dir2check[i][1]*srchrad;
139                  tdir[2] = -ndp->vray[2];
140 <                if (normalize(tdir) == 0)
134 <                        continue;
140 >                normalize(tdir);
141                  ec = SDevalBSDF(&sv, tdir, ndp->vray, ndp->sd);
142                  if (ec)
143                          goto baderror;
# Line 148 | Line 154 | compute_through(BSDFDAT *ndp)
154                  goto baderror;
155          if (tomega > 1.5*dfp->minProjSA)
156                  return;                         /* not really a peak? */
157 <        if ((bright(vpeak) - ndp->sd->tLamb.cieY*(1./PI))*tomega <= .001)
158 <                return;                         /* < 0.1% transmission */
157 >        if ((bright(vpeak) - ndp->sd->tLamb.cieY*(1./PI))*tomega <= .007)
158 >                return;                         /* < 0.7% transmission */
159          for (i = 3; i--; )                      /* remove peak from average */
160                  colval(vsum,i) -= colval(vpeak,i);
161          --nsum;
# Line 184 | Line 190 | direct_specular_OK(COLOR cval, FVECT ldir, double omeg
190   {
191          int     nsamp, ok = 0;
192          FVECT   vsrc, vsmp, vjit;
193 <        double  tomega;
193 >        double  tomega, tomega2;
194          double  sf, tsr, sd[2];
195          COLOR   csmp, cdiff;
196          double  diffY;
197          SDValue sv;
198          SDError ec;
199          int     i;
200 +                                        /* in case we fail */
201 +        setcolor(cval, .0, .0, .0);
202                                          /* transform source direction */
203          if (SDmapDir(vsrc, ndp->toloc, ldir) != SDEnone)
204                  return(0);
# Line 219 | Line 227 | direct_specular_OK(COLOR cval, FVECT ldir, double omeg
227                  diffY = .0;
228                  setcolor(cdiff, .0, .0, .0);
229          }
230 <                                        /* assign number of samples */
230 >                                        /* need projected solid angles */
231 >        omega *= fabs(vsrc[2]);
232          ec = SDsizeBSDF(&tomega, ndp->vray, vsrc, SDqueryMin, ndp->sd);
233          if (ec)
234                  goto baderror;
235                                          /* check indirect over-counting */
236 <        if ((ndp->thick != 0 || bright(ndp->cthru) > FTINY)
237 <                                && ndp->pr->crtype & (SPECULAR|AMBIENT)
238 <                                && (vsrc[2] > 0) ^ (ndp->vray[2] > 0)) {
236 >        if (ndp->pr->crtype & (SPECULAR|AMBIENT)
237 >                                && (vsrc[2] > 0) ^ (ndp->vray[2] > 0)
238 >                                && bright(ndp->cthru) > FTINY) {
239                  double  dx = vsrc[0] + ndp->vray[0];
240                  double  dy = vsrc[1] + ndp->vray[1];
241 <                if (dx*dx + dy*dy <= omega+tomega)
241 >                if (dx*dx + dy*dy <= (4./PI)*(omega + tomega +
242 >                                                2.*sqrt(omega*tomega)))
243                          return(0);
244          }
245 +                                        /* assign number of samples */
246          sf = specjitter * ndp->pr->rweight;
247          if (tomega <= .0)
248                  nsamp = 1;
# Line 240 | Line 251 | direct_specular_OK(COLOR cval, FVECT ldir, double omeg
251          else
252                  nsamp = 4.*sf*omega/tomega + .5;
253          nsamp += !nsamp;
254 <        setcolor(cval, .0, .0, .0);     /* sample our source area */
244 <        sf = sqrt(omega);
254 >        sf = sqrt(omega);               /* sample our source area */
255          tsr = sqrt(tomega);
256          for (i = nsamp; i--; ) {
257                  VCOPY(vsmp, vsrc);      /* jitter query directions */
# Line 249 | Line 259 | direct_specular_OK(COLOR cval, FVECT ldir, double omeg
259                          multisamp(sd, 2, (i + frandom())/(double)nsamp);
260                          vsmp[0] += (sd[0] - .5)*sf;
261                          vsmp[1] += (sd[1] - .5)*sf;
262 <                        if (normalize(vsmp) == 0) {
253 <                                --nsamp;
254 <                                continue;
255 <                        }
262 >                        normalize(vsmp);
263                  }
264                  bsdf_jitter(vjit, ndp, tsr);
265                                          /* compute BSDF */
266                  ec = SDevalBSDF(&sv, vjit, vsmp, ndp->sd);
267                  if (ec)
268                          goto baderror;
269 <                if (sv.cieY - diffY <= FTINY) {
263 <                        addcolor(cval, cdiff);
269 >                if (sv.cieY - diffY <= FTINY)
270                          continue;       /* no specular part */
271 <                }
271 >                                        /* check for variable resolution */
272 >                ec = SDsizeBSDF(&tomega2, vjit, vsmp, SDqueryMin, ndp->sd);
273 >                if (ec)
274 >                        goto baderror;
275 >                if (tomega2 < .12*tomega)
276 >                        continue;       /* not safe to include */
277                  cvt_sdcolor(csmp, &sv);
278                  addcolor(cval, csmp);   /* else average it in */
279                  ++ok;
280          }
281 <        if (!ok) {
282 <                setcolor(cval, .0, .0, .0);
283 <                return(0);              /* no valid specular samples */
284 <        }
274 <        sf = 1./(double)nsamp;
281 >        if (!ok)                        /* no valid specular samples? */
282 >                return(0);
283 >
284 >        sf = 1./(double)ok;             /* compute average BSDF */
285          scalecolor(cval, sf);
286                                          /* subtract diffuse contribution */
287          for (i = 3*(diffY > FTINY); i--; )

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