solstice-solver

commit 56d72fdef2d5755e21f4d511c770940415694516
parent e8f0312b136e47536a9fe8ac81dc87b67c2f6207
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Fri,  7 Apr 2017 20:53:12 +0200

Fix perturbated normals in the path-tracer

Handle the inconsistency of the sampled direction around the
shading normal wrt to the geometric normal, i.e. the sampled direction
must point on the right surface side wrt the sampled BSDF component.

Diffstat:
M
src/ssol_draw_pt.c
 | 
24
+++++++++++++++++++++---

1 file changed, 21 insertions(+), 3 deletions(-)
diff --git a/src/ssol_draw_pt.c b/src/ssol_draw_pt.c
@@ -143,12 +143,16 @@ Li(struct ssol_scene* scn,
   double L = 0;
   double R;
   double pdf;
+  double cos_wi_Ng;
   const float ray_range[2] = {0, FLT_MAX};
   float ray_org[3];
   float ray_dir[3];
   enum ssol_side_flag side;
   int russian_roulette = 0;
   int type;
+  int reject_sample;
+  int nfailures;
+  const int MAX_FAILURES = 10;
   res_T res = RES_OK;
   ASSERT(scn && view && org && dir && val);
 
@@ -225,16 +229,30 @@ Li(struct ssol_scene* scn,
         (scn->sun, view, &ray_data, ctx->bsdf, wo, frag.Ns, ray_org);
     }
 
-    R = ssf_bsdf_sample(ctx->bsdf, ctx->rng, wo, frag.Ns, wi, &type, &pdf);
-    ASSERT(0 <= R && R <= 1);
+    /* Sampling a bounce direction */
+    nfailures = 0;
+    do {
+      reject_sample = 0;
+      R = ssf_bsdf_sample(ctx->bsdf, ctx->rng, wo, frag.Ns, wi, &type, &pdf);
+      ASSERT(0 <= R && R <= 1);
+      cos_wi_Ng = d3_dot(wi, frag.Ng);
+      if(((type & SSF_TRANSMISSION) && cos_wi_Ng > 0)
+      || ((type & SSF_REFLECTION)   && cos_wi_Ng < 0)) {
+        /* Reject inconsistent direction due to normal perturbation exepted if
+         * no other direction can be generated */
+        R = 0;
+        reject_sample = (++nfailures < MAX_FAILURES && !(type & SSF_SPECULAR));
+      }
+    } while(reject_sample);
     f3_set_d3(ray_dir, wi);
+
     if(type & SSF_TRANSMISSION) material_get_next_medium(mtl, &medium, &medium);
 
     if(!russian_roulette) {
       throughput *= fabs(d3_dot(wi, frag.Ns)) * R;
     } else {
       if(ssp_rng_canonical(ctx->rng) >= R) break;
-      throughput *= d3_dot(wi, frag.Ns);
+      throughput *= fabs(d3_dot(wi, frag.Ns));
     }
 
     if(throughput <= 0) break;