From 3e41274f45735fa6e93ae346eafc8738a056d846 Mon Sep 17 00:00:00 2001
From: Anton Ljungdahl <anton.ljungdahl@fysik.su.se>
Date: Fri, 25 Apr 2025 23:47:57 +0200
Subject: [PATCH] diffuse skylight

---
 src/main.cu   |  21 +++++++++++++++------
 timeBuild.ctm | Bin 2468 -> 2500 bytes
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/main.cu b/src/main.cu
index 0d6780b..cb56bfe 100644
--- a/src/main.cu
+++ b/src/main.cu
@@ -488,10 +488,10 @@ get_sample_color(RayF32 ray, Entity *entities, curandState *local_rand_state)
   Vec3F32 out = {0};
 
   F32 current_attenuation = 1.0f;
+  F32 attenuation_factor = 0.5f;
   Vec3F32 sample_pixel_color = vec3F32(0.0f, 0.0f, 0.0f);
   for(U32 bounce_idx = 0; 
-      //bounce_idx < MAX_DIFFUSE_DEPTH; 
-      bounce_idx < 1; 
+      bounce_idx < MAX_DIFFUSE_DEPTH; 
       bounce_idx += 1)
   {
 
@@ -524,14 +524,18 @@ get_sample_color(RayF32 ray, Entity *entities, curandState *local_rand_state)
 
     if(hit_rec.hit)
     {
-      // Paint entity
+      // "Paint entity"
+      // For a diffuse color we actually just update the attenuation here and 
+      // bounce rays around... Then when we are not hitting anything anymore we will sample
+      // the background gradient and use the computed attenuation. Since the rays are
+      // bouncing diffusely this will shade nicely.
       Vec3F32 rand_dir = rand_unit_vector_on_hemisphere_F32(local_rand_state, hit_rec.normal);
-      current_attenuation = current_attenuation * 0.5f;
+      current_attenuation = current_attenuation * attenuation_factor;
 
       current_ray.origin = hit_rec.point;
       current_ray.direction = rand_dir;
-      sample_pixel_color = add_V3F32(hit_rec.normal, vec3F32(1.0f, 1.0f, 1.0f));
-      sample_pixel_color = scale_V3F32(0.5f, sample_pixel_color);
+      //sample_pixel_color = add_V3F32(hit_rec.normal, vec3F32(1.0f, 1.0f, 1.0f));
+      //sample_pixel_color = scale_V3F32(0.5f, sample_pixel_color);
       // debug
       //sample_pixel_color = vec3F32(1.0f, 0.0f, 0.0f);
     }
@@ -547,6 +551,7 @@ get_sample_color(RayF32 ray, Entity *entities, curandState *local_rand_state)
       F32 blend = 0.5f*(unit_dir.y + 1.0f);
 
       sample_pixel_color = lerp_V3F32(blend, white, light_blue);
+      // Scale by the current attenuation for diffuse shading using background color
       sample_pixel_color = scale_V3F32(current_attenuation, sample_pixel_color);
       break;
     }
@@ -568,7 +573,11 @@ cuda_main(Entity *entities, Vec3F32 *pixelbuffer, curandState *rand_state)
   if(x < image.width && y < image.height)
   {
 
+    // NOTE! We need to pass this as a pointer to subsequent usage functions, in order
+    // to update the random state on this thread, after each call to a distribution function.
     curandState local_rand_state = rand_state[idx];
+
+
     // We are adding all samples and then dividing by num samples to get the mean, so 
     // we initialise the color for this pixel to black.
     // Loop over all pixel samples
diff --git a/timeBuild.ctm b/timeBuild.ctm
index 24f69157b8a6549c5d3d2869e18f7c7e0d622d16..619dfc043a807c80a5751abb7baa5ad078dcc212 100644
GIT binary patch
delta 40
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delta 7
OcmX>iyhM1z5>5aNwgT(`