Cycles Denoising: Get rid of halos around bright edges

Previously, bright edges (e.g. caused by rim lighting) would sometimes get
halos around them after denoising.

This change introduces a log(1+x) highlight compression step that is performed
before denoising and reversed afterwards. That way, the denoising algorithm
itself operates in the compressed space and therefore bright edges cause less
numerical issues.

1 files changed, 13 insertions, 0 deletions

diff --git a/intern/cycles/render/denoising.cpp b/intern/cycles/render/denoising.cpp
index 82bbfa5f823..39bd8ce00c2 100644
--- a/intern/cycles/render/denoising.cpp
+++ b/intern/cycles/render/denoising.cpp
@@ -491,6 +491,19 @@ bool DenoiseTask::load_input_pixels(int layer)
       }
     }
 
+    /* Highlight compression */
+    data = buffer_data + 8;
+    for (int y = 0; y < h; y++) {
+      for (int x = 0; x < w; x++) {
+        int idx = INPUT_NUM_CHANNELS * (y * w + x);
+        float3 color = make_float3(data[idx], data[idx + 1], data[idx + 2]);
+        color = color_highlight_compress(color, NULL);
+        data[idx] = color.x;
+        data[idx + 1] = color.y;
+        data[idx + 2] = color.z;
+      }
+    }
+
     buffer_data += frame_stride;
   }