Cycles: make AO bounces settings more discoverable

* Move out of Simplify panel, into Light Paths > Fast Global Illumination
* Add separate boolan setting to enable/disable it separate from Simplify
* Default AO bounces to 1
* Put ambient occlusion distance in this panel as well

intern/cycles/blender/addon/properties.py

@@ -801,17 +801,22 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
         items=enum_texture_limit
     )
 
+    use_fast_gi: BoolProperty(
+        name="Fast GI Approximation",
+        description="Approximate diffuse indirect light with background tinted ambient occlusion. This provides fast alternative to full global illumination, for interactive viewport rendering or final renders with reduced quality",
+        default=False,
+    )
     ao_bounces: IntProperty(
         name="AO Bounces",
-        default=0,
-        description="Approximate indirect light with background tinted ambient occlusion at the specified bounce, 0 disables this feature",
+        default=1,
+        description="After this number of light bounces, use approximate global illumination. 0 disables this feature",
         min=0, max=1024,
     )
 
     ao_bounces_render: IntProperty(
         name="AO Bounces Render",
-        default=0,
-        description="Approximate indirect light with background tinted ambient occlusion at the specified bounce, 0 disables this feature",
+        default=1,
+        description="After this number of light bounces, use approximate global illumination. 0 disables this feature",
         min=0, max=1024,
     )
 

intern/cycles/blender/addon/ui.py

@@ -526,6 +526,35 @@ class CYCLES_RENDER_PT_light_paths_caustics(CyclesButtonsPanel, Panel):
         col.prop(cscene, "caustics_refractive", text="Refractive")
 
 
+class CYCLES_RENDER_PT_light_paths_fast_gi(CyclesButtonsPanel, Panel):
+    bl_label = "Fast GI Approximation"
+    bl_options = {'DEFAULT_CLOSED'}
+    bl_parent_id = "CYCLES_RENDER_PT_light_paths"
+
+    def draw_header(self, context):
+        scene = context.scene
+        cscene = scene.cycles
+
+        self.layout.prop(cscene, "use_fast_gi", text="")
+
+    def draw(self, context):
+        scene = context.scene
+        cscene = scene.cycles
+        world = scene.world
+
+        layout = self.layout
+        layout.use_property_split = True
+        layout.use_property_decorate = False
+
+        col = layout.column(align=True)
+        col.prop(cscene, "ao_bounces", text="Viewport Bounces")
+        col.prop(cscene, "ao_bounces_render", text="Render Bounces")
+
+        if world:
+          light = world.light_settings
+          layout.prop(light, "distance", text="AO Distance")
+
+
 class CYCLES_RENDER_PT_motion_blur(CyclesButtonsPanel, Panel):
     bl_label = "Motion Blur"
     bl_options = {'DEFAULT_CLOSED'}
@@ -2041,7 +2070,6 @@ class CYCLES_RENDER_PT_simplify_viewport(CyclesButtonsPanel, Panel):
         col.prop(rd, "simplify_subdivision", text="Max Subdivision")
         col.prop(rd, "simplify_child_particles", text="Child Particles")
         col.prop(cscene, "texture_limit", text="Texture Limit")
-        col.prop(cscene, "ao_bounces", text="AO Bounces")
         col.prop(rd, "simplify_volumes", text="Volume Resolution")
 
 
@@ -2067,7 +2095,6 @@ class CYCLES_RENDER_PT_simplify_render(CyclesButtonsPanel, Panel):
         col.prop(rd, "simplify_subdivision_render", text="Max Subdivision")
         col.prop(rd, "simplify_child_particles_render", text="Child Particles")
         col.prop(cscene, "texture_limit_render", text="Texture Limit")
-        col.prop(cscene, "ao_bounces_render", text="AO Bounces")
 
 
 class CYCLES_RENDER_PT_simplify_culling(CyclesButtonsPanel, Panel):
@@ -2245,6 +2272,7 @@ classes = (
     CYCLES_RENDER_PT_light_paths_max_bounces,
     CYCLES_RENDER_PT_light_paths_clamping,
     CYCLES_RENDER_PT_light_paths_caustics,
+    CYCLES_RENDER_PT_light_paths_fast_gi,
     CYCLES_RENDER_PT_volumes,
     CYCLES_RENDER_PT_subdivision,
     CYCLES_RENDER_PT_hair,

intern/cycles/blender/addon/version_update.py

@@ -217,6 +217,15 @@ def do_versions(self):
                         baov.name = caov.get("name", "AOV")
                         baov.type = "COLOR" if caov.get("type", 1) == 1 else "VALUE"
 
+            if version <= (2, 93, 16):
+                cscene = scene.cycles
+                if scene.render.use_simplify and \
+                   (cscene.ao_bounces or cscene.ao_bounces_render):
+                    cscene.use_fast_gi = True
+                else:
+                    cscene.ao_bounces = 1
+                    cscene.ao_bounces_render = 1
+
         # Lamps
         for light in bpy.data.lights:
             if light.library not in libraries:

intern/cycles/blender/blender_sync.cpp

@@ -358,7 +358,7 @@ void BlenderSync::sync_integrator()
 
   integrator->set_adaptive_min_samples(adaptive_min_samples);
 
-  if (b_scene.render().use_simplify()) {
+  if (get_boolean(cscene, "use_fast_gi")) {
     if (preview) {
       integrator->set_ao_bounces(get_int(cscene, "ao_bounces"));
     }

source/blender/blenkernel/BKE_blender_version.h

@@ -39,7 +39,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 16
+#define BLENDER_FILE_SUBVERSION 17
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and show a warning if the file