fixed assertion, renamed some methods, tweaked code.

src/appleseed/renderer/kernel/lighting/drt/drtlightingengine.cpp

@@ -384,8 +384,8 @@ namespace
                     const double light_sample_count = max(m_params.m_dl_light_sample_count, 1.0);
                     const double mis_weight =
                         mis_power2(
-                            1.0 * vertex.get_bsdf_point_prob(),
-                            light_sample_count * vertex.get_light_point_prob(m_light_sampler));
+                            1.0 * vertex.get_prev_prob_area(),
+                            light_sample_count * vertex.get_light_prob_area(m_light_sampler));
                     emitted_radiance *= static_cast<float>(mis_weight);
                 }
 

src/appleseed/renderer/kernel/lighting/pathtracer.h

@@ -403,10 +403,10 @@ size_t PathTracer<PathVisitor, Adjoint>::trace(
             sampling_context.split_in_place(3, 1);
             const foundation::Vector3d s = sampling_context.next_vector2<3>();
 
-            // Select one incoming point at random.
+            // Select one of the incoming points at random.
             const size_t sample_index = foundation::truncate<size_t>(s[0] * visitor.m_sample_count);
             const ShadingPoint& incoming_point = visitor.m_incoming_points[sample_index];
-            const double probability = visitor.m_probabilities[sample_index] / visitor.m_sample_count;
+            const double probability = visitor.m_probabilities[sample_index];
             const double eta = visitor.m_etas[sample_index];
 
             // Compute Fresnel coefficient at outgoing point.
@@ -415,7 +415,7 @@ size_t PathTracer<PathVisitor, Adjoint>::trace(
             if (outgoing_fresnel <= 0.0)
                 break;
 
-            // Pick an incoming direction.
+            // Pick an incoming direction at random.
             foundation::Vector3d incoming_vector =
                 foundation::sample_hemisphere_cosine(foundation::Vector2d(s[1], s[2]));
             const double cos_in = incoming_vector.y;
@@ -447,6 +447,7 @@ size_t PathTracer<PathVisitor, Adjoint>::trace(
                 * incoming_fresnel
                 * outgoing_fresnel
                 * cos_in
+                * visitor.m_sample_count
                 / (probability * incoming_prob);
             value = rd;
             value *= static_cast<float>(weight);

src/appleseed/renderer/kernel/lighting/pathvertex.h

@@ -107,10 +107,10 @@ class PathVertex
         Spectrum&               radiance) const;
 
     // Return the probability density wrt. surface area mesure of reaching this vertex via BSDF sampling.
-    double get_bsdf_point_prob() const;
+    double get_prev_prob_area() const;
 
     // Return the probability density wrt. surface area mesure of reaching this vertex via light sampling.
-    double get_light_point_prob(const LightSampler& light_sampler) const;
+    double get_light_prob_area(const LightSampler& light_sampler) const;
 };
 
 
@@ -163,20 +163,18 @@ inline const Material* PathVertex::get_material() const
     return m_shading_point->get_material();
 }
 
-inline double PathVertex::get_bsdf_point_prob() const
+inline double PathVertex::get_prev_prob_area() const
 {
-    // Make sure we're coming from a valid BSDF scattering event.
-    assert(m_prev_mode == ScatteringMode::Diffuse ||
-           m_prev_mode == ScatteringMode::Glossy ||
-           m_prev_mode == ScatteringMode::Specular);
+    // Make sure we're coming from a valid scattering event.
+    assert(m_prev_mode != ScatteringMode::Absorption);
     assert(m_prev_prob > 0.0);
 
     // Veach: 8.2.2.2 eq. 8.10.
     const double d = m_shading_point->get_distance();
     return m_prev_prob * m_cos_on / (d * d);
 }
 
-inline double PathVertex::get_light_point_prob(const LightSampler& light_sampler) const
+inline double PathVertex::get_light_prob_area(const LightSampler& light_sampler) const
 {
     return light_sampler.evaluate_pdf(*m_shading_point);
 }

src/appleseed/renderer/kernel/lighting/pt/ptlightingengine.cpp

@@ -935,8 +935,8 @@ namespace
                     const double light_sample_count = max(m_params.m_dl_light_sample_count, 1.0);
                     const double mis_weight =
                         mis_power2(
-                            1.0 * vertex.get_bsdf_point_prob(),
-                            light_sample_count * vertex.get_light_point_prob(m_light_sampler));
+                            1.0 * vertex.get_prev_prob_area(),
+                            light_sample_count * vertex.get_light_prob_area(m_light_sampler));
                     emitted_radiance *= static_cast<float>(mis_weight);
                 }