From a64e85601c3d9fbd630d5d377e7c7cc168315e0e Mon Sep 17 00:00:00 2001
From: Stefan Zellmann <info@szellmann.de>
Date: Sun, 13 Oct 2024 15:50:11 +0200
Subject: [PATCH] Use real light dist for shadow offset computation

---
 renderer/DirectLight_impl.cpp |  6 ++---
 renderer/Raycast_impl.cpp     |  4 ++--
 renderer/common.h             | 41 +++++++++++++++++++++++++----------
 3 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/renderer/DirectLight_impl.cpp b/renderer/DirectLight_impl.cpp
index 8075beaa..6db5197f 100644
--- a/renderer/DirectLight_impl.cpp
+++ b/renderer/DirectLight_impl.cpp
@@ -174,10 +174,10 @@ bool shade(ScreenSample &ss, Ray &ray, unsigned worldID,
                                      viewDir,
                                      ls.dir,
                                      ls.intensity);
-          shadedColor = shadedColor * safe_rcp(ls.pdf) / (ls.dist*ls.dist);
+          shadedColor = shadedColor * safe_rcp(ls.pdf) / ls.dist2;
         }
         else
-          shadedColor = hrv.albedo * ls.intensity * safe_rcp(ls.pdf) / (ls.dist*ls.dist);
+          shadedColor = hrv.albedo * ls.intensity * safe_rcp(ls.pdf) / ls.dist2;
       } else {
         const auto &geom = onDevice.geometries[group.geoms[hr.geom_id]];
         const auto &mat = onDevice.materials[group.materials[hr.geom_id]];
@@ -190,7 +190,7 @@ bool shade(ScreenSample &ss, Ray &ray, unsigned worldID,
                                    viewDir,
                                    ls.dir,
                                    ls.intensity);
-        shadedColor = shadedColor * safe_rcp(ls.pdf) / (ls.dist*ls.dist);
+        shadedColor = shadedColor * safe_rcp(ls.pdf) / ls.dist2;
       }
     }
     else if (rendererState.renderMode == RenderMode::Ng)
diff --git a/renderer/Raycast_impl.cpp b/renderer/Raycast_impl.cpp
index 6a3e9002..4dbedde7 100644
--- a/renderer/Raycast_impl.cpp
+++ b/renderer/Raycast_impl.cpp
@@ -66,7 +66,7 @@ inline PixelSample renderSample(ScreenSample &ss, Ray ray, unsigned worldID,
       for (unsigned lightID=0; lightID<world.numLights; ++lightID) {
         const dco::Light &light = onDevice.lights[world.allLights[lightID]];
 
-        light_sample<float> ls = sampleLight(light, hitPos, ss.random);
+        LightSample ls = sampleLight(light, hitPos, ss.random);
 
         float3 brdf = evalMaterial(mat,
                                    onDevice.samplers,
@@ -76,7 +76,7 @@ inline PixelSample renderSample(ScreenSample &ss, Ray ray, unsigned worldID,
                                    viewDir,
                                    ls.dir,
                                    ls.intensity);
-        shadedColor += brdf / ls.pdf / (ls.dist*ls.dist);
+        shadedColor += brdf / ls.pdf / ls.dist2;
       }
 
       shadedColor +=
diff --git a/renderer/common.h b/renderer/common.h
index 11f0c7a6..ff03caa6 100644
--- a/renderer/common.h
+++ b/renderer/common.h
@@ -741,27 +741,46 @@ inline vec3 evalMaterial(const dco::Material &mat,
   return shadedColor;
 }
 
-typedef light_sample<float> LightSample;
+struct LightSample : light_sample<float>
+{
+  float3 intensity;
+  float3 dir;
+  float pdf;
+  float dist;
+  float dist2;
+};
 
 VSNRAY_FUNC
 inline LightSample sampleLight(const dco::Light &light, vec3f hitPos, Random &rnd)
 {
   LightSample result;
+  light_sample<float> ls;
   if (light.type == dco::Light::Point) {
-    result = light.asPoint.sample(hitPos, rnd);
-    result.intensity = light.asPoint.intensity(hitPos);
+    ls = light.asPoint.sample(hitPos, rnd);
+    ls.intensity = light.asPoint.intensity(hitPos);
   } else if (light.type == dco::Light::Quad) {
-    result = light.asQuad.sample(hitPos, rnd);
-    result.intensity = light.asQuad.intensity(hitPos);
+    ls = light.asQuad.sample(hitPos, rnd);
+    ls.intensity = light.asQuad.intensity(hitPos);
   } else if (light.type == dco::Light::Directional) {
-    result = light.asDirectional.sample(hitPos, rnd);
-    result.intensity = light.asDirectional.intensity(hitPos);
+    ls = light.asDirectional.sample(hitPos, rnd);
+    ls.intensity = light.asDirectional.intensity(hitPos);
   } else if (light.type == dco::Light::HDRI) {
-    result = light.asHDRI.sample(hitPos, rnd);
-    result.intensity = light.asHDRI.intensity(result.dir);
+    ls = light.asHDRI.sample(hitPos, rnd);
+    ls.intensity = light.asHDRI.intensity(result.dir);
   }
-  float dist = result.dist;
-  result.dist = light.type == dco::Light::Directional||dco::Light::HDRI ? 1.f : dist;
+
+  result.intensity = ls.intensity;
+  result.dir = ls.dir;
+  result.pdf = ls.pdf;
+  result.dist = ls.dist;
+
+  if (light.type == dco::Light::Directional
+    ||light.type == dco::Light::HDRI) {
+    result.dist2 = 1.f; // infinite lights are not attenuated by distance!
+  } else {
+    result.dist2 = ls.dist*ls.dist;
+  }
+
   return result;
 }