[Bf-blender-cvs] [630d2b64974] master: Cycles: allow Adaptive Sampling with Scrambling Distance

[Brecht Van Lommel]

Commit: 630d2b649741c9d9f7bc0857054b001eede84a80
Author: Brecht Van Lommel
Date:   Tue Mar 15 16:08:10 2022 +0100
Branches: master
https://developer.blender.org/rB630d2b649741c9d9f7bc0857054b001eede84a80

Cycles: allow Adaptive Sampling with Scrambling Distance

While the correlation may not work well with adaptive sampling, in practice
this appears to work ok in most cases

Automatic scrambling distance uses the minimum samples from adaptive sampling,
which provides a good default estimate to avoid artifacts.

Contributed by Alaska.

Differential Revision: https://developer.blender.org/D13325

===================================================================

M	intern/cycles/blender/addon/properties.py
M	intern/cycles/blender/addon/ui.py
M	intern/cycles/blender/sync.cpp

===================================================================

diff --git a/intern/cycles/blender/addon/properties.py b/intern/cycles/blender/addon/properties.py
index a0741c0633d..4f78fbfc9e7 100644
--- a/intern/cycles/blender/addon/properties.py
+++ b/intern/cycles/blender/addon/properties.py
@@ -349,7 +349,7 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
         name="Scrambling Distance",
         default=1.0,
         min=0.0, soft_max=1.0,
-        description="Reduce randomization between pixels to improve GPU rendering performance, at the cost of possible rendering artifacts if set too low. Only works when not using adaptive sampling",
+        description="Reduce randomization between pixels to improve GPU rendering performance, at the cost of possible rendering artifacts if set too low",
     )
     preview_scrambling_distance: BoolProperty(
         name="Scrambling Distance viewport",
@@ -360,7 +360,7 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
     auto_scrambling_distance: BoolProperty(
         name="Automatic Scrambling Distance",
         default=False,
-        description="Automatically reduce the randomization between pixels to improve GPU rendering performance, at the cost of possible rendering artifacts. Only works when not using adaptive sampling",
+        description="Automatically reduce the randomization between pixels to improve GPU rendering performance, at the cost of possible rendering artifacts",
     )
 
     use_layer_samples: EnumProperty(
diff --git a/intern/cycles/blender/addon/ui.py b/intern/cycles/blender/addon/ui.py
index 64de1227355..1f50f3da7ae 100644
--- a/intern/cycles/blender/addon/ui.py
+++ b/intern/cycles/blender/addon/ui.py
@@ -289,11 +289,8 @@ class CYCLES_RENDER_PT_sampling_advanced(CyclesButtonsPanel, Panel):
         layout.separator()
 
         heading = layout.column(align=True, heading="Scrambling Distance")
-        heading.active = not (cscene.use_adaptive_sampling and cscene.use_preview_adaptive_sampling)
         heading.prop(cscene, "auto_scrambling_distance", text="Automatic")
-        sub = heading.row()
-        sub.active = not cscene.use_preview_adaptive_sampling
-        sub.prop(cscene, "preview_scrambling_distance", text="Viewport")
+        heading.prop(cscene, "preview_scrambling_distance", text="Viewport")
         heading.prop(cscene, "scrambling_distance", text="Multiplier")
 
         layout.separator()
diff --git a/intern/cycles/blender/sync.cpp b/intern/cycles/blender/sync.cpp
index d4949a5ff30..8af2ee7a435 100644
--- a/intern/cycles/blender/sync.cpp
+++ b/intern/cycles/blender/sync.cpp
@@ -346,31 +346,48 @@ void BlenderSync::sync_integrator(BL::ViewLayer &b_view_layer, bool background)
       cscene, "sampling_pattern", SAMPLING_NUM_PATTERNS, SAMPLING_PATTERN_SOBOL);
   integrator->set_sampling_pattern(sampling_pattern);
 
+  int samples = 1;
   bool use_adaptive_sampling = false;
   if (preview) {
+    samples = get_int(cscene, "preview_samples");
     use_adaptive_sampling = RNA_boolean_get(&cscene, "use_preview_adaptive_sampling");
     integrator->set_use_adaptive_sampling(use_adaptive_sampling);
     integrator->set_adaptive_threshold(get_float(cscene, "preview_adaptive_threshold"));
     integrator->set_adaptive_min_samples(get_int(cscene, "preview_adaptive_min_samples"));
   }
   else {
+    samples = get_int(cscene, "samples");
     use_adaptive_sampling = RNA_boolean_get(&cscene, "use_adaptive_sampling");
     integrator->set_use_adaptive_sampling(use_adaptive_sampling);
     integrator->set_adaptive_threshold(get_float(cscene, "adaptive_threshold"));
     integrator->set_adaptive_min_samples(get_int(cscene, "adaptive_min_samples"));
   }
 
-  int samples = get_int(cscene, "samples");
   float scrambling_distance = get_float(cscene, "scrambling_distance");
   bool auto_scrambling_distance = get_boolean(cscene, "auto_scrambling_distance");
   if (auto_scrambling_distance) {
+    if (samples == 0) {
+      /* If samples is 0, then viewport rendering is set to render infinitely. In that case we
+       * override the samples value with 4096 so the Automatic Scrambling Distance algorithm
+       * picks a Scrambling Distance value with a good balance of performance and correlation
+       * artifacts when rendering to high sample counts. */
+      samples = 4096;
+    }
+
+    if (use_adaptive_sampling) {
+      /* If Adaptive Sampling is enabled, use "min_samples" in the Automatic Scrambling Distance
+       * algorithm to avoid artifacts common with Adaptive Sampling + Scrambling Distance. */
+      const AdaptiveSampling adaptive_sampling = integrator->get_adaptive_sampling();
+      samples = min(samples, adaptive_sampling.min_samples);
+    }
     scrambling_distance *= 4.0f / sqrtf(samples);
   }
 
-  /* only use scrambling distance in the viewport if user wants to and disable with AS */
+  /* Only use scrambling distance in the viewport if user wants to. */
   bool preview_scrambling_distance = get_boolean(cscene, "preview_scrambling_distance");
-  if ((preview && !preview_scrambling_distance) || use_adaptive_sampling)
+  if (preview && !preview_scrambling_distance) {
     scrambling_distance = 1.0f;
+  }
 
   if (scrambling_distance != 1.0f) {
     VLOG(3) << "Using scrambling distance: " << scrambling_distance;