Fix to ignore geometric term for non area lights

Author: Sopiro

sample/scene/cornell_box.cpp

@@ -66,12 +66,12 @@ std::unique_ptr<Camera> CornellBox(Scene& scene)
         // auto mat = CreateThinDielectricMaterial(scene, 1.5f);
 
         auto tf = Transform{ 0.66f, hy, -0.33f, Quat(DegToRad(-18.0f), y_axis), Vec3(hx * 2.0f, hy * 2.0f, hz * 2.0f) };
-        // CreateBox(scene, tf, right_box);
+        CreateBox(scene, tf, right_box);
     }
 
     // Right sphere
     {
-        CreateSphere(scene, Transform(Vec3(0.65f, 0.15f, -0.3f), Quat(DegToRad(0), x_axis)), 0.15f, glass);
+        // CreateSphere(scene, Transform(Vec3(0.65f, 0.15f, -0.3f), Quat(DegToRad(0), x_axis)), 0.15f, rough_glass);
     }
 
     // Lights

src/integrator/bidirectional_path_integrator.cpp

@@ -100,8 +100,11 @@ int32 BiDirectionalPathIntegrator::SampleLightPath(Vertex* path, Sampler& sample
         v.pdf_rev = 0;
     }
 
-    Spectrum beta =
-        light_sample.Le * AbsDot(light_sample.normal, light_sample.ray.d) / (sl.pmf * light_sample.pdf_p * light_sample.pdf_w);
+    Spectrum beta = light_sample.Le / (sl.pmf * light_sample.pdf_p * light_sample.pdf_w);
+    if (light_sample.normal != Vec3::zero)
+    {
+        beta *= AbsDot(light_sample.normal, light_sample.ray.d);
+    }
 
     // Note light paths sample one fewer vertex than the target path length
     return 1 + RandomWalk(

src/integrator/light_path_integrator.cpp

@@ -69,8 +69,11 @@ Spectrum LightPathIntegrator::L(
     int32 bounce = 0;
     Ray ray = light_sample.ray;
 
-    Spectrum beta =
-        light_sample.Le * AbsDot(light_sample.normal, ray.d) / (sampled_light.pmf * light_sample.pdf_p * light_sample.pdf_w);
+    Spectrum beta = light_sample.Le / (sampled_light.pmf * light_sample.pdf_p * light_sample.pdf_w);
+    if (light_sample.normal != Vec3::zero)
+    {
+        beta *= AbsDot(light_sample.normal, ray.d);
+    }
 
     // Trace light path
     while (true)

src/integrator/light_vol_path_integrator.cpp

@@ -70,8 +70,12 @@ Spectrum LightVolPathIntegrator::L(
     int32 bounce = 0;
     Ray ray = light_sample.ray;
 
-    Spectrum beta =
-        light_sample.Le * AbsDot(light_sample.normal, ray.d) / (sampled_light.pmf * light_sample.pdf_p * light_sample.pdf_w);
+    Spectrum beta = light_sample.Le / (sampled_light.pmf * light_sample.pdf_p * light_sample.pdf_w);
+    if (light_sample.normal != Vec3::zero)
+    {
+        beta *= AbsDot(light_sample.normal, ray.d);
+    }
+
     Spectrum r_u(1);
 
     // Trace light path