Glitter: add spatial energy compensation

1 files changed, 5 insertions, 3 deletions

diff --git a/glitter.cginc b/glitter.cginc
index 09ba0ea..ebacffe 100644
--- a/glitter.cginc
+++ b/glitter.cginc
@@ -152,10 +152,11 @@ float integrate_box(float2 x, float2 size, float2 mu, float2x2 sigma,
         sqrt(sigma[1][1]), lower_limit.y, upper_limit.y);
 }
 
-float compensation(float2 x_a, float2x2 sigma_a, float res_a) {
-  float containing = integrate_box(0.5, 0.5, x_a, sigma_a, 0.0, 1.0);
+float compensation(float2 x, float2x2 sigma, float res) {
+  float containing = integrate_box(0.5, 0.5, x, sigma, 0.0, 1.0);
+  float2 sampled_cell_center = (floor(x * res) + 0.5) / res;
   float explicitly_evaluated =
-    integrate_box(round(x_a*res_a)/res_a, 1.0/res_a, x_a, sigma_a, 0, 1);
+    integrate_box(sampled_cell_center, 1.0 / res, x, sigma, 0, 1);
   return containing - explicitly_evaluated;
 }
 
@@ -217,6 +218,7 @@ float D_Kemppinen(float3 h, float alpha, float glint_alpha, float2 uv,
       best_g_a = g_a;
     }
     D_filter += w_lambda * compensation(x_a, sigma_a, res_a);
+    D_filter += w_lambda * compensation(x_s, sigma_s, res_s);
   }
 
   micro_normal = normalize(disk_to_ndf_ggx(best_g_a, alpha));